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Carbapenem-resistant Acinetobacter baumannii (CRAB) is a persistent nosocomial pathogen that poses a significant threat to global public health, particularly in intensive care units (ICUs). Here we report a three-month longitudinal genomic surveillance study conducted in a Hangzhou ICU in 2021. This followed a three-month study conducted in the same ICU in 2019, and infection prevention and control (IPC) interventions targeting patients, staff and the ICU environment. Most A. baumannii isolated in this ICU in 2021 were CRAB (80.9%; 419/518) with higher-level resistance to carbapenems. This was accompanied by the proportion of global clone 2 (GC2) isolates falling from 99.5% in 2019 to 50.8% (213/419) in 2021. The phylogenetic diversity of GC2 increased, apparently driven by regular introductions of distinct clusters in association with patients. The remaining CRAB (40.2%; 206/419) were a highly clonal population of ST164. Isolates of ST164 carried bla NDM-1 and bla OXA-23 carbapenemase genes, and exhibited higher carbapenem MIC 50 /MIC 90 values than GC2. Comparative analysis of publicly available genomes from 26 countries (five continents) revealed that ST164 has evolved towards carbapenem resistance on multiple independent occasions. Its success in this ICU and global capacity for acquiring resistance determinants indicate that ST164 CRAB is an emerging high-risk lineage of global concern., (© 2024. The Author(s).)

Carbapenem-Resistant Acinetobacter baumannii (CRAB) outbreak in intensive care units (ICUs) is a significant problem for healthcare facilities. In this study, we aimed to investigate the occurrence of CRAB isolates among ICU-admitted patients during the three waves of the COVID-19 pandemic in Iran using Multiple-Locus Variable Number Tandem-Repeat Analysis (MLVA). We obtained 50 (A) baumannii isolates from tracheal aspirate and blood culture samples. In the disc diffusion method, all isolates were cefotaxime, ceftriaxone, and cefepime-resistant, while 98% (49/50) of isolates were resistant to piperacillin, piperacillin-tazobactam, ceftazidime, and ciprofloxacin. Levofloxacin and tobramycin resistance was found in 76% (38/50) of isolates. In the microbroth dilution test all isolates were resistant to imipenem, 98% (49/50) to meropenem, 68% (34/50) to colistin, and 20% (10/50) to polymyxin (B) Based on the PCR findings, all isolates harbored bla OXA-40 , ISAba-1, and int-2 genes. There were no isolates found that have the bla OXA-58 , bla OXA-143 , bla VEB-1 , bla VIM , and int-3 genes. Among Extended-spectrum beta-lactamases (ESBL) genes, bla CTX-M , bla TEM , bla SHV , bla GES , and bla PER-1 have a prevalence of 42% (21/50), 84% (42/50), 58% (29/50), 78% (39/50), and 54% (27/50), respectively. 74% (37/50) of the isolates had the bla OXA-23 gene, while all of the isolates carried the bla OXA-40 gene. Among MBL genes, bla IPM , bla GIM , bla SIM , and bla NDM-1 have a prevalence of 20% (10/50), 8% (4/50), 22% (11/50), and 60% (30/50), respectively. The prevalence of int-1 was documented as 74% (37/50). Accordingly, all isolates were identified as CRAB. The co-existence of bla OXA-23 /int-2 and bla OXA-23 /isaba-1 was 74% (37/50). The co-existence of bla NDM-1 /ISAba-1 was observed in 30 (60%) isolates. Using an 80% similarity threshold on the dendrogram constructed through MLVA typing, all isolates were grouped into two clusters: cluster A with 9 isolates from wave 3, and cluster B with 41 isolates from waves 3, 4, and 5. Our study confirms a clonal transmission of CRAB during the study period and suggests using molecular typing methods like MLVA in healthcare settings to identify dominant clones, antibiotic resistance patterns, and transmission routes. This will help to better manage the emergence and spread of antibiotic-resistant strains in future outbreaks., (© 2024. The Author(s).)

The carbapenem-resistant Acinetobacter baumannii isolate BAL062 is a clinical reference isolate used in several recent experimental studies. It is from a ventilator-associated pneumonia (VAP) patient in an intensive care unit at the Hospital for Tropical Diseases (HTD), Ho Chi Minh City, Vietnam in 2009. Here, BAL062 was found to belong to the B sub-lineage of global clone 2 (GC2) isolates in the previously reported outbreak (2008 and 2012) of carbapenem-resistant VAP A. baumannii at the HTD. While related sub-lineage B outbreak isolates were extensively antibiotic-resistant and carry GC2-associated genomic resistance islands, AbGRI1, AbGRI2, and AbGRI3, BAL062 has lost AbGRI3 and three aminoglycoside resistance genes, armA, aacA4, and aphA1 , leading to amikacin, tobramycin and kanamycin susceptibility. The location of Tn 2008 VAR found in the chromosome of this sub-lineage was also corrected. Like many of the outbreak isolates, BAL062 carries the KL58 gene cluster at the capsular polysaccharide (CPS) synthesis locus and an annotation key is provided. As information about K type is important for the development of novel CPS-targeting therapies, the BAL062 K58-type CPS structure was established using NMR spectroscopy. It is most closely related to K2 and K93, sharing similar configurations and linkages between K units, and contains the rare higher monosaccharide, 5,7-diacetamido-3,5,7,9-tetradeoxy-d- glycero -l- manno -non-2-ulosonic acid (5,7-di- N -acetyl-8-epipseudaminic acid; 8ePse5Ac7Ac), the 8-epimer of Pse5Ac7Ac (5,7-di- N -acetylpseudaminic acid). Inspection of publicly available A. baumannii genomes revealed a wide distribution of the KL58 locus in geographically diverse isolates belonging to several sequence types that were recovered over two decades from clinical, animal, and environmental sources.IMPORTANCEMany published experimental studies aimed at developing a clearer understanding of the pathogenicity of carbapenem-resistant Acinetobacter baumannii strains currently causing treatment failure due to extensive antibiotic resistance are undertaken using historic, laboratory-adapted isolates. However, it is ideal if not imperative that recent clinical isolates are used in such studies. The clinical reference isolate characterized here belongs to the dominant A. baumannii GC2 clone causing extensively resistant infections and has been used in various recent studies. The correlation of resistance profiles and resistance gene data is key to identifying genes available for gene knockout and complementation analyses, and we have mapped the antibiotic resistance genes to find candidates. Novel therapies, such as bacteriophage or monoclonal antibody therapies, currently under investigation as alternatives or adjuncts to antibiotic treatment to combat difficult-to-treat CRAb infections often exhibit specificity for specific structural epitopes of the capsular polysaccharide (CPS), the outer-most polysaccharide layer. Here, we have solved the structure of the CPS type found in BAL062 and other extensively resistant isolates. As consistent gene naming and annotation are important for locus identification and interpretation of experimental studies, we also have correlated automatic annotations to the standard gene names., Competing Interests: The authors declare no conflict of interest.

Background: The treatment of carbapenem-resistant Acinetobacter baumannii/calcoaceticus complex (CRAB) presents significant treatment challenges., Methods: We report the case of a 42-year-old woman with CRAB meningitis who experienced persistently positive cerebrospinal fluid (CSF) cultures for 13 days despite treatment with high-dose ampicillin-sulbactam and cefiderocol. On day 13, she was transitioned to sulbactam-durlobactam and meropenem; 4 subsequent CSF cultures remained negative. After 14 days of sulbactam-durlobactam, she was cured of infection. Whole genome sequencing investigations identified putative mechanisms that contributed to the reduced cefiderocol susceptibility observed during cefiderocol therapy. Blood and CSF samples were collected pre-dose and 3-hours post initiation of a sulbactam-durlobactam infusion., Results: The CRAB isolate belonged to sequence type 2. An acquired blaOXA-23 and an intrinsic blaOXA-51-like (ie, blaOXA-66) carbapenemase gene were identified. The paradoxical effect (ie, no growth at lower cefiderocol dilutions but growth at higher dilutions) was observed by broth microdilution after 8 days of cefiderocol exposure but not by disk diffusion. Potential markers of resistance to cefiderocol included mutations in the start codon of piuA and piuC iron transport genes and an A515V substitution in PBP3, the primary target of cefiderocol. Sulbactam and durlobactam were detected in CSF at both timepoints, indicating CSF penetration., Conclusions: This case describes successful treatment of refractory CRAB meningitis with the administration of sulbactam-durlobactam and meropenem and highlights the need to be cognizant of the paradoxical effect that can be observed with broth microdilution testing of CRAB isolates with cefiderocol., Competing Interests: Potential conflicts of interest . S. M. K. and P. J. S. served on an Advisory Board for Entasis/Innoviva Specialty Therapeutics. P. J. S. reports grants from T2 Diagnostics and Accelerate Diagnostics, grants and personal fees from bioMérieux, Inc., and Qiagen Sciences Inc.; and personal fees from BD Diagnostics, Shionogi, Inc., GeneCapture, Day Zero Diagnostics, Next Gen Diagnostics, outside the submitted work. All other authors report no potential conflicts. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed., (© The Author(s) 2024. Published by Oxford University Press on behalf of Infectious Diseases Society of America. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Background: The global threat of Carbapenem-resistant Acinetobacter baumannii (CRAB) has intensified as resistance to carbapenems continues to rise in recent decades. We aimed to explore risk factors, molecular epidemiology, and antimicrobial therapy of CRAB infection., Methods: The clinical data of 110 patients infected with A. baumannii from December 2021 to December 2022 were retrospectively analyzed. Patients were divided into a carbapenem-resistance group (55 patients) and carbapenem-sensitive group (CSAB; 55 patients) based on resistance to carbapenem, and the risk factors of patients infected with CRAB were analyzed. Fifty-five patients with CRAB infection who received antimicrobial therapy were divided into a combination therapy group (45 patients) and a monotherapy group (10 patients), and differences between the two groups were compared. Whole-genome sequencing analysis was performed to assess resistance genes. Phylogenetic analysis was performed to explore the characteristics of CRAB isolates., Results: Among the total 110 patients, the rate of poor prognosis in the CRAB group was 43.6% (24/55). Mechanical ventilation (odds ratio [OR] = 5.364, 95% confidence interval [CI] 1.462-19.679, P = 0.011) and puncture (OR = 19.935, 95% CI 1.261-315.031, P = 0.012) were independent risk factors for CRAB infection. Of 55 patients in the antimicrobial regimen study, 45 received combination therapy (including dual, triple, or quadruple antibiotic therapy) and 10 received monotherapy. Univariate analysis revealed significant differences between the combination group and monotherapy group for admission to the intensive care unit and wound infection (P < 0.05). The CRAB strains of 26 patients taking carbapenem-based combination therapy were mainly ST208, ST1968, and ST195, among which patients with ST1968 strains had higher 28-day mortality. Furthermore, the bla OXA-23 gene was harbored in ST1968, ST195, and ST208., Conclusions: Mortality was significantly higher in patients infected with CRAB than with CSAB. Mechanical ventilation and puncture were independent risk factors in predicting CRAB infections. The distribution of CRAB was dominated by ST208, ST1968, and ST195, among which patients with ST1968 had higher 28-day mortality. The bla OXA-23 gene appears to be widely disseminated., (© 2024. The Author(s).)

Background and Objectives: Of the genes conferring resistance to carbapenems in Acinetobacter baumannii, the bla OXA-23 gene is the most widely found across the world. The gene carrying bla OXA-23 transposons in A. baumannii isolates of global clones GC1 and GC2 is found worldwide. Here, we examined whether transposons play a role in the dissemination of the bla OXA-23 in globally distributed clones, GC1 and GC2 A. baumannii isolates from Iraq., Materials and Methods: The 119 non-repetitive A. baumannii isolates including 94 recovered from clinical specimens and 25 isolates from hospital environment between September 2021 and April 2022 from different medical centers located at various regions in Baghdad, Iraq. The global clones (GC) and the genes encoding carbapenem resistance, including bla OXA-23 , bla OXA-24 , and bla OXA-58 were identified using multiplex PCR assays. Antibiotic susceptibility testing was performed by the Kirby-Bauer disk diffusion susceptibility method. The transposons carrying bla OXA-23 were examined using PCR mapping. In cases when carbapenem susceptible A. baumannii isolates were found, they were subjected to E test, full length sequencing of bla OXA-Ab (bla OXA-51-like ) and Institut Pasteur multi-locus sequence typing scheme., Results: All but two isolates (92 clinical and 25 environmental) were identified carbapenem-resistant A. baumannii (CRAB). Of 117 CRAB isolates, 20 belong to GC1, 19 contained bla OXA-23 ; of them, 17 isolates harbored the bla OXA-23 located on Tn2006. Among the 46 CRAB belonging to GC2, 39 contained bla OXA-23 ; of them, 34 carried the bla OXA-23 located on Tn2006. The remaining GC1 and GC2 isolates, one GC1 as well as one GC2 isolate, were susceptible to imipenem, doripenem, and meropenem and considered carbapenem-susceptible A. baumannii (CSAB). Full-length sequencing of the bla OXA-Ab and MLST for the two CSAB isolates belonging to GC1 and GC2 confirmed that the GC1 isolate belongs to ST 623 and contained an allele that encodes an bla OXA-69 variant of the bla OXA-Ab while the GC2 belong to ST2 and carried an bla OXA-66 variant., Conclusion: This study provides evidence for the dissemination of bla OXA-23 on the Tn2006 in CRAB isolates in Baghdad, Iraq. It appears that this transposon is widespread in GC1 and 2 isolates as in the other parts of the world. Interestingly, one GC1 and one GC2 isolate from Iraq were found to be susceptible to carbapenem while the isolates belonging to GC1 and GC2 have so far rarely been found to be susceptible to carbapenem globally., (© 2024. The Author(s).)

Cefiderocol, a siderophore-cephalosporine conjugate antibiotic, shows promise as a therapeutic option for carbapenem-resistant (CR) Acinetobacter infections. While resistance has already been reported in A. baumannii , combination therapies with avibactam or sulbactam reduce MICs of cefiderocol, extending its efficacy. However, careful consideration is necessary when using these combinations. In our experiments, exposure of A. baumannii and A. lwoffii to cefiderocol and sulbactam or avibactam led to the selection of cefiderocol-resistant strains. Three of those were subjected to whole genome sequencing and transcriptomic analysis. The strains all possessed synonymous and non-synonymous substitutions and short deletions. The most significant mutations affected efflux pumps, transcriptional regulators, and iron homeostasis genes. Transcriptomics showed significant alterations in expression levels of outer membrane proteins, iron homeostasis, and β-lactamases, suggesting adaptive responses to selective pressure. This study underscores the importance of carefully assessing drug synergies, as they may inadvertently foster the selection of resistant variants and complicate the management of CR Acinetobacter infections.IMPORTANCEThe emergence of carbapenem-resistant Acinetobacter strains as a serious global health threat underscores the urgent need for effective treatment options. Although few drugs show promise against CR Acinetobacter infections, resistance to both drugs has been reported. In this study, the molecular characterization of spontaneous cefiderocol-resistant variants, a CR A. baumannii strain with antagonism to sulbactam, and an A. lwoffii strain with antagonism to avibactam, provides valuable insights into the mechanisms of resistance to cefiderocol. Some mechanisms observed are associated with mutations affecting efflux pumps, regulators, and iron homeostasis genes. These findings highlight the importance of understanding resistance mechanisms to optimize treatment options. They also emphasize the importance of early evaluation of drug synergies to address the challenges of antimicrobial resistance in Acinetobacter infections., Competing Interests: The authors declare no conflict of interest.

Introduction: There are multiple ongoing outbreaks of carbapenem resistant Acinetobacter baumannii (CR Ab ) infection in Fiji's hospitals. CR Ab is able to colonize and persist on various hospital surfaces for extended periods. We conducted a study to understand the extent of hospital environmental contamination and phylogenetic links with clinical isolates., Methods: Swabs were collected from high-touch surfaces at Colonial War Memorial Hospital (CWMH) September 2021 and December 2022; Lautoka Hospital (LTKH) August 2022; and Labasa Hospital (LBSH) November 2022. All bacterial isolates were identified, and antimicrobial susceptibility testing (AST) performed; isolates resistant to carbapenems and producing a carbapenemase underwent whole genome sequencing. Comparison was made to clinical isolates obtained from CWMH in 2016-2017 and 2019-2021 and from LTKH and LBSH from 2020-2021., Results: From the 180 environmental samples collected, ten (5.6%) CR Ab were isolated; no other carbapenem-resistant gram-negative organisms were isolated. Seven (70%) of the CR Ab were isolated from CWMH and three (30%) from LTKH; no CR Ab were isolated from LBSH. Of the seven CWMH CR Ab , two were sequence type 2 (ST2), three ST25, and two ST499. All LTKH isolates were ST499. The two environmental CR Ab ST2 isolates were closely genetically linked to isolates obtained from patients in CWMH, LTKH, and LBSH 2020-2021. Similarly, the three environmental CR Ab ST25 isolates were closely genetically linked to isolates obtained from patients admitted to CWMH in 2019-2021 and LBSH in 2020. The environmental CR Ab ST499 isolates represented two distinct clones, with clone 1 comprising two genetically identical isolates from CWMH and clone 2 the three isolates from LTKH. Although no genetic linkages were observed when comparing environmental ST499 isolates to those from CWMH patients in 2020-2021, both clone 1 isolates were genetically identical to an isolate obtained from a patient admitted during the sampling period., Conclusion: Our study highlights the contamination of high-touch surfaces within Fiji hospitals with CR Ab , suggesting that these may serve as important sources for CR Ab . Phylogenetic linkages to CR Ab isolated from patients since 2019 underscores the persistence of this resistant pathogen in hospital settings and the ongoing risk for hospital-acquired infections., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Baleivanualala, Matanitobua, Samisoni, Soqo, Smita, Mailulu, Nabose, Lata, Shayam, Sharma, Wilson, Crump and Ussher.)

Background: Carbapenem-resistant Acinetobacter baumannii (CRAB) frequently causes both healthcare-associated infections and nosocomial outbreaks in burn medicine/plastic surgery and beyond. Owing to the high antibiotic resistance, infections are difficult to treat, and patient outcomes are often compromised. The environmental persistence capability of CRAB favors its transmission in hospitals. A comprehensive analysis and understanding of CRAB epidemiology and microbiology are essential for guiding management., Methods: A three-year retrospective cohort study (2020-2022) was conducted in a German tertiary burn and plastic surgery center. In addition to epidemiological analyses, microbiological and molecular techniques, including whole-genome sequencing, were applied for the comprehensive examination of isolates from CRAB-positive patients., Results: During the study period, eight CRAB cases were found, corresponding to an overall incidence of 0.2 CRAB cases per 100 cases and an incidence density of 0.35 CRAB cases per 1000 patient-days. Six cases (75%) were treated in the burn intensive care unit, and four cases (50%) acquired CRAB in the hospital. Molecular analyses comprising 74 isolates supported the epidemiologic assumption that hospital acquisitions occurred within two separate clusters. In one of these clusters, environmental CRAB contamination of anesthesia equipment may have enabled transmission. Furthermore, molecular diversity of CRAB isolates within patients was observed., Conclusions: CRAB can pose a challenge in terms of infection prevention and control, especially if cases are clustered in time and space on a ward. Our study demonstrates that high-resolution phylogenetic analysis of several bacterial isolates from single patients can greatly aid in understanding transmission chains and helps to take precision control measures., (© 2024. The Author(s).)

Carbapenem-resistant Acinetobacter baumannii (CRAB) poses a significant threat to hospitalized patients as effective therapeutic options are scarce. Based on the genomic characteristics of the CRAB strain AB2877 harboring chromosome-borne bla OXA-23 , which was isolated from the bronchoalveolar lavage fluid (BALF) of a patient in a respiratory intensive care unit (RICU), we systematically analyzed antibiotic resistance genes (ARGs) and the genetic context associated with ARGs carried by CRAB strains harboring chromosome-borne bla OXA-23 worldwide. Besides bla OXA-23 , other ARGs were detected on the chromosome of the CRAB strain AB2877 belonging to ST208/1806 (Oxford MLST scheme). Several key genetic contexts associated with the ARGs were identified on the chromosome of the CRAB strain AB2877, including (1) the MDR region associated with bla OXA-23 , tet(B)-tetR(B ), aph(3'')-Ib, and aph(6)-Id (2); the resistance island AbGRI3 harboring armA and mph(E)-msr(E ) (3); the Tn 3 -like composite transposon containing bla TEM-1D and aph(3')-Ia ; and (4) the structure "IS Aba1-bla ADC-25 ." The first two genetic contexts were most common in ST195/1816, followed by ST208/1806. The last two genetic contexts were found most frequently in ST208/1806, followed by ST195/1816.IMPORTANCEThe bla OXA-23 gene can be carried by plasmid or chromosome, facilitating horizontal genetic transfer and increasing carbapenem resistance in healthcare settings. In this study, we focused on the genomic characteristics of CRAB strains harboring the chromosome-borne bla OXA-23 gene, and the important genetic contexts associated with bla OXA-23 and other ARGs were identified, and their prevalent clones worldwide were determined. Notably, although the predominant clonal CRAB lineages worldwide containing the MDR region associated with bla OXA-23 , tet(B)-tetR(B ), aph(3'')-Ib, and aph (6)-Id was ST195/1816, followed by ST208/1806, the CRAB strain AB2877 in our study belonged to ST208/1806. Our findings contribute to the knowledge regarding the dissemination of CRAB strains and the control of nosocomial infection., Competing Interests: The authors declare no conflict of interest.

Nosocomial outbreaks caused by carbapenem-resistant Acinetobacter baumannii (CRAB) strains are rapidly emerging worldwide and are cause for concern. Herein, we aimed to describe the genomic characteristics of CRAB strains isolated from two hospitals in China in 2023. The A. baumannii isolates were mainly collected from the ICU and isolated from the sputum (71.43%, 15/21), followed by urine (14.29%, 3/21). Twenty-one A. baumannii strains possessed a multidrug-resistant (MDR) profile, and whole-genome sequencing showed that they all carried bla OXA-23 . Based on the Pasteur multilocus sequence typing (MLST) scheme, all strains were typed into a sequence type 2 (ST2). Based on the Oxford MLST scheme, six strains belonged to ST540, three of which were ST208, and four strains were assigned to ST784. Kaptive showed most of the strains (38.10%, 8/21) contained KL93. As for the lipoolygosaccharide (OC locus) type, OCL1c and OCL1d were identified, accounting for 33.33% (7/21) and 66.67% (14/21), respectively. Based on the BacWGSTdb server, we found that the strains belonging to ST540 and ST784 were all collected from China. However, the ST938 strains were isolated from Malaysia and Thailand. Comparative genomics analysis showed that the AB10 strain had a closed relationship with SXAB10-SXAB13 strains, suggesting the transmission happened in these two hospitals and other hospital in China. In addition, the 4300STDY7045869 strain, which was collected from Thailand, possessed near genetic relationship with our isolates in this study, suggesting the possible spread among various countries. Additionally, 3-237 single nucleotide polymorphisms were observed among these strains. In conclusion, this study conducted a genome-based study for A. baumannii strains collected from two hospitals in China and revealed their epidemiological and molecular features. Clone spreading occurred in these two hospitals. Hence, there is an urgent need for increased surveillance in hospitals and other clinical settings to prevent and control CRAB spreading., Competing Interests: Declaration of competing interest The authors declare that there is no conflict of interest., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Background: Understanding the epidemiology of carbapenem-resistant A. baumannii complex (CRAB) and the patients impacted is an important step toward informing better infection prevention and control practices and improving public health response., Methods: Active, population-based surveillance was conducted for CRAB in 9 U.S. sites from January 1 to December 31, 2019. Medical records were reviewed, isolates were collected and characterized including antimicrobial susceptibility testing and whole genome sequencing., Results: Among 136 incident cases in 2019, 66 isolates were collected and characterized; 56.5% were from cases who were male, 54.5% were from persons of Black or African American race with non-Hispanic ethnicity, and the median age was 63.5 years. Most isolates, 77.2%, were isolated from urine, and 50.0% were collected in the outpatient setting; 72.7% of isolates harbored an acquired carbapenemase gene (aCP), predominantly bla OXA-23 or bla OXA-24/40 ; however, an isolate with bla NDM was identified. The antimicrobial agent with the most in vitro activity was cefiderocol (96.9% of isolates were susceptible)., Conclusions: Our surveillance found that CRAB isolates in the U.S. commonly harbor an aCP, have an antimicrobial susceptibility profile that is defined as difficult-to-treat resistance, and epidemiologically are similar regardless of the presence of an aCP., (Published by Elsevier Inc.)

Carbapenem-resistant significant members of Acinetobacter calcoaceticus-Acinetobacter baumannii (CR-SM-ACB) complex have emerged as an important cause of sepsis, especially in ICUs. This study demonstrates the application of loop-mediated-isothermal-amplification (LAMP) assay for detection of CR-SM-ACB-complex from patients with sepsis. Whole-blood and culture-broths(CB) collected from patients with culture-positive sepsis were subjected to LAMP and compared with PCR, and RealAmp. Vitek-2 system and conventional PCR results were used as confirmatory references. The sensitivity and specificity of LAMP(97 % & 100 %) and RealAmp(100 % & 100 %) for detection of CR-SM-ACB-complex from CB were better than PCR(87 % & 100 %). Diagnostic accuracy of LAMP, RealAmp, and PCR for detection of SM-ACB-complex from CB was 98.5 %, 100 %, and 88.5 % respectively. Turnaround time of Culture, LAMP, PCR, and RealAmp was 28-53, 6-20, 9-23, and 6-20hours, respectively. LAMP is a simple, inexpensive tool that can be applied directly to positive CB and may be customized to detect emerging pathogens and locally-prevalent resistance genes and to optimize antimicrobial use., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Inc.)

The emergence and spread of Acinetobacter baumannii pose a severe threat to public health, highlighting the urgent need for the next generation of therapeutics due to its increasing resistance to existing antibiotics. BfmR, a response regulator modulating virulence and antimicrobial resistance, shows a promising potential as a novel antimicrobial target. Developing BfmR inhibitors may propel a new therapeutic direction for intractable infection of resistant strains. In this study, we conducted a structure-based hierarchical virtual screening pipeline combining molecular docking, molecular dynamic simulation, and MM/GBSA calculation to sift the Specs chemical library and finally discover three novel potential BfmR inhibitors. The three hits can reduce the MIC of meropenem for the carbapenem-resistant Acinetobacter baumannii (CRAB) strain ZJ06. Similar to the BfmR knockout strain, Cmp-98 was demonstrated to downregulate the expression of K locus genes, indicating it as a BfmR inhibitor. Bacteria underwent harmful morphological changes after treatment with these inhibitors. Molecular dynamic simulations found that all the hits tend to dynamically bind to different positions of the phosphorylation site of BfmR. Wherein we identified a potential inhibitory-binding cleft, beside a possible activated binding cleft at the edge of the phosphorylation site. Restraining the ligand binding poses may help exert inhibitory effects. This study reports a group of new scaffold BfmR inhibitors, offering new insights for novel antibiotic therapeutics against CRAB.

Carbapenem-resistant Acinetobacter baumannii (CRAB) is a major human pathogen and a research priority for developing new antimicrobial agents. CRAB is a causative agent of a variety of infections in different body sites. One of the manifestations is catheter-associated urinary tract infection, which exposes the bacteria to the host's urine, creating a particular environment. Exposure of two CRAB clinical isolates, AB5075 and AMA40, to human urine (HU) resulted in the differential expression levels of 264 and 455 genes, respectively, of which 112 were common to both strains. Genes within this group play roles in metabolic pathways such as phenylacetic acid (PAA) catabolism, the Hut system, the tricarboxylic acid (TCA) cycle, and other processes like quorum sensing and biofilm formation. These results indicate that the presence of HU induces numerous adaptive changes in gene expression of the infecting bacteria. These changes presumably help bacteria establish and thrive in the hostile conditions in the urinary tract. These analyses advance our understanding of CRAB's metabolic adaptations to human fluids, as well as expand knowledge on bacterial responses to distinct human fluids containing different concentrations of human serum albumin (HSA)., (© 2024. The Author(s).)

The Acinetobacter calcoaceticus-baumannii (ACB) complex, also known as ACB complex, consists of four bacterial species that can cause opportunistic infections in humans, especially in hospital settings. Conventional therapies for susceptible strains of the ACB complex include broad-spectrum cephalosporins, β -lactam/ β -lactamase inhibitors, and carbapenems. Unfortunately, the effectiveness of these antibiotics has declined due to increasing rates of resistance. The predominant resistance mechanisms identified in the ACB complex involve carbapenem-resistant (CR) oxacillinases and metallo- β -lactamases (MBLs). This research, conducted at Kathmandu Model Hospital in Nepal, sought to identify genes associated with CR, specifically bla NDM-1, bla OXA-23-like, and bla OXA-24-like genes in carbapenem-resistant Acinetobacter calcoaceticus-baumannii (CR-ACB) complex. Additionally, the study is aimed at identifying the ACB complex through the sequencing of the 16s rRNA gene. Among the 992 samples collected from hospitalized patients, 43 (approximately 4.334%) tested positive for the ACB complex. These positive samples were mainly obtained from different hospital units, including intensive care units (ICUs); cabins; and neonatal, general, and maternity wards. The prevalence of infection was higher among males (58.14%) than females (41.86%), with the 40-50 age group showing the highest infection rate. In susceptibility testing, colistin and polymyxin B exhibited a susceptibility rate of 100%, whereas all samples showed resistance to third-generation cephalosporins. After polymyxins, gentamicin (30.23%) and amikacin (34.88%) demonstrated the highest susceptibility. A substantial majority (81.45%) of ACB complex isolates displayed resistance to carbapenems, with respiratory and pus specimens being the primary sources. Polymerase chain reaction (PCR) revealed that the primary CR gene within the ACB complex at this hospital was bla OXA-23-like , followed by bla NDM-1 . To ensure the accuracy of the phenotypic assessment, 12 samples were chosen for 16s rRNA sequencing using Illumina MiSeq™ to confirm that they are Acinetobacter species. QIIME 2.0 analysis confirmed all 12 isolates to be Acinetobacter species. In the hospital setting, a substantial portion of the ACB complex carries CR genes, rendering carbapenem ineffective for treatment., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2024 Anupama Gurung et al.)

Wastewater treatment plants (WWTPs) have been implicated as direct key reservoir of both antibiotic-resistant bacteria (ARB) and antibiotic-resistant genes (ARGs) associated with human infection, as high concentrations of ARBs and ARGs have been detected in recycled hospital wastewater. Among the ARBs, the carbapenem-resistant Acinetobacter baumannii has been ranked as priority 1 (critical) pathogen by the World Health Organization (WHO), due to its overwhelming burden on public health. Therefore, this study is aimed at investigating non-thermal plasma (NTP) technology as an alternative disinfection step to inactivate this bacterium and its ARGs. Culture-based method and PCR were employed in confirming the carbapenem resistance gene bla NDM-1 in A. baumannii (BAA 1605). Suspension of carbapenem-resistant A. baumannii (24 h culture) was prepared from the confirmed isolate and subjected to plasma treatment at varying time intervals (3 min, 6 min, 9 min, 12 min, and 15 min) in triplicates. The plasma-treated samples were evaluated for re-growth and the presence of the resistance gene. The treatment resulted in a 1.13 log reduction after 3 min and the highest log reduction of ≥ 8 after 15 min, and the results also showed that NTP was able to inactivate the bla NDM-1 gene. The log reduction and gel image results suggest that plasma disinfection has a great potential to be an efficient tertiary treatment step for WWTPs., (© 2024. The Author(s).)

Tandem amplification of carbapenemase genes increases gene copy number and enhances carbapenem resistance. These amplifications are often heterogeneous, transient, and located on plasmids, which also contribute to heteroresistance. Amplification of encoding genes is especially important for enzymes with low hydrolysis activity, which are often overlooked. Here, we reported an intrinsic oxacillinase oxaAb amplification flanked by ISAba1. The amplification is in the chromosome and contains up to 25 repeats. We provided genomic, transcriptomic, and proteomic evidence that the amplification resulted in oxacillinase overproduction. Notably, no point mutations of oxaAb were found during the amplification process. Strains of Acinetobacter baumannii with intrinsic amplified or external transformed ISAba1-oxaAb exhibited higher meropenem hydrolysis activity. Furthermore, the number of repeats in the amplification decreased gradually over a period of 21 d cultured with carbapenem withdrawal. However, upon re-exposure to meropenem, the ISAba1 flanked oxaAb responded rapidly, with repeat numbers reaching or exceeding pre-carbapenem withdrawal levels within 24 h. Taken together, these findings suggest that ISAba1-mediated gene amplification and overproduction of intrinsic low-activity oxacillinase oxaAb resulted in carbapenem resistance., (Copyright © 2024 Elsevier Ltd and International Society of Antimicrobial Chemotherapy. All rights reserved.)

Introduction: Acinetobacter baumannii (AB) is rising as a human pathogen of critical priority worldwide as it is the leading cause of opportunistic infections in healthcare settings and carbapenem-resistant AB is listed as a "super bacterium" or "priority pathogen for drug resistance" by the World Health Organization., Methods: Clinical isolates of A. baumannii were collected and tested for antimicrobial susceptibility. Among them, carbapenem-resistant and carbapenem-sensitive A. baumannii were subjected to prokaryotic transcriptome sequencing. The change of sRNA and mRNA expression was analyzed by bioinformatics and validated by quantitative reverse transcription-PCR., Results: A total of 687 clinical isolates were collected, of which 336 strains of A. baumannii were resistant to carbapenem. Five hundred and six differentially expressed genes and nineteen differentially expressed sRNA candidates were discovered through transcriptomic profile analysis between carbapenem-resistant isolates and carbapenem-sensitive isolates. Possible binding sites were predicted through software for sRNA21 and adeK , sRNA27 and pgaC , sRNA29 and adeB , sRNA36 and katG , indicating a possible targeting relationship. A negative correlation was shown between sRNA21 and adeK (r = -0.581, P = 0.007), sRNA27 and pgaC (r = -0.612, P = 0.004), sRNA29 and adeB (r = -0.516, P = 0.020)., Discussion: This study preliminarily screened differentially expressed mRNA and sRNA in carbapenem-resistant A. baumannii , and explored possible targeting relationships, which will help further reveal the resistance mechanism and provide a theoretical basis for the development of drugs targeting sRNA for the prevention and treatment of carbapenem-resistant A. baumannii infection., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Wei, Xin, Zhang, Liao, Rong, Zhong, Zhao, Ma and He.)

We report the emergence of cefiderocol resistance in a bla OXA-72 carbapenem-resistant Acinetobacter baumannii isolate from a sacral decubitus ulcer. Cefiderocol was initially used; however, a newly approved sulbactam-durlobactam therapy with source control and flap coverage was successful in treating the infection. Laboratory investigation revealed cefiderocol resistance mediated by IS Aba36 insertion into the siderophore receptor pirA ., Competing Interests: The authors declare no conflict of interest.

Background and Objectives: Acinetobacter baumannii ( A. baumannii ), particularly carbapenem-resistant A. baumannii (CRAB), represents a grave concern in healthcare settings and is associated with high mortality. This study aimed to conduct molecular, mutational, and phylogenetic analyses of specific genes in CRAB and evaluate the synergistic effects of selected antimicrobial combinations. Materials and Methods : Phenotypic characterization was performed on six CRAB strains by using the Modified Hodge Test (MHT) and IMP-EDTA Double-Disc Synergy Test (IMP-EDTA DDST). Carbapenemase- and metallo-beta-lactamase-encoding genes were amplified by using Polymerase Chain Reaction. Phylogenetic analysis using the MEGA 11 tool was used to determine the evolutionary relatedness of these genes. Mutational analysis was performed by using I-Mutant, MUPro, and PHD-SNP bioinformatics tools to predict mutations in the carbapenemase-encoding genes. Microdilution checkerboard titration assessed the synergistic effects of antimicrobial combinations (azithromycin-meropenem, rifampicin-meropenem, meropenem-colistin, and azithromycin-colistin) on these CRAB isolates. Results : The phenotypic characterization of six CRAB isolates revealed positive results for MHT and IMP-EDTA DDST. The molecular characterization revealed that carbapenemase- and MBL-encoding genes were present in all isolates with varying frequencies, including blaOXA-51 (100%) and blaIMP (0%). The sequence analysis revealed high evolutionary relatedness to sequences in the NCBI database. The mutational analysis identified 16 mutations, of which 1 mutation (P116L) in the blaOXA-58 gene predicted a change in the protein product, potentially contributing to carbapenem resistance. The checkerboard titration method did not reveal any synergism among the tested antimicrobial combinations against CRAB. Conclusion : This study's findings underscore the significant challenges posed by CRAB isolates harboring multiple resistant genes in treatment. This highlights the urgent need for novel antimicrobial agents, a crucial step towards reducing mortality rates not only in Pakistan but also globally.

We present our findings on interpatient transmission, epidemic control measures, and the outcomes of a series of ten critically ill burn patients who were either colonized or infected with carbapenem-resistant Acinetobacter baumannii (CRAB). None of the five infected patients achieved clinical cure, and all experienced relapses. Microbiological failure was observed in 40% of the infected patients. The isolated CRAB strains were found to carry bla OXA-23 and armA resistance genes. Despite the lack of clinical cure, all five infected patients survived and were discharged from the Burn Intensive Care Unit., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Introduction: Our goal was to investigate the antimicrobial resistance due to beta-lactamase genes and virulent determinants (biofilm-forming ability) expressed by Acinetobacter collected from health settings in Pakistan. A cross-sectional study was conducted for the molecular characterization of carbapenemases and biofilm-producing strains of Acinetobacter spp., Methodology: Two twenty-three imipenem-resistant Acinetobacter isolates were analyzed from 2020 to 2023.The combination disk test and modified hodge test were performed. Biofilm forming ability was determined by polystyrene tube assay. Multiplex polymerase chain reaction (PCR) for virulent and biofilm-forming genes, and 16S rRNA sequencing were performed., Results: 118 (52.9%) carbapenem-resistant Acinetobacter (CR-AB) were isolated from wounds and pus, 121 (54.2%) from males, and 92 (41.2%) from 26-50-years-olds. More than 80% of strains produced β-lactamases and carbapenemases. Based on the PCR amplification of the ITS gene, 174 (78.0%) CR-AB strains were identified from CR-Acinetobacter non-baumannii (ANB). Most CR-AB were strong and moderate biofilm producers. Genetic analysis revealed the blaOXA-23, blaTEM, blaCTX-M blaNDM-1 and blaVIM were prevalent in CR-AB with frequencies 91 (94.8%), 68 (70.8%), 19 (19.7%), 53 (55.2%), 2 (2.0%) respectively. Among virulence genes, OmpA was dominant in CR-AB isolates from wound (83, 86.4%), csuE 63 (80.7%) from non-wound specimens and significantly correlated with blaNDM and blaOXA genes. Phylogenetic analysis revealed three different clades for strains based on specimens., Conclusions: CR-AB was highly prevalent in Pakistan and associated with wound infections. The genes, blaOXA-23, blaTEM, blaCTX-M, and blaNDM-1 were detected in CR-AB. Most CR-AB were strong biofilm producers with virulent genes OmpA and csuE., Competing Interests: No Conflict of Interest is declared, (Copyright (c) 2024 Maqsood Arif, Amina Asif, Kiran Nazeer, Sikander Sultan, Saba Riaz.)

Introduction: A complex interplay between Acinetobacter spp., patients, and the environment has made it increasingly difficult to optimally treat patients infected with Acinetobacter spp., mainly due to rising antimicrobial resistance and challenges with surveillance., Objectives: This study evaluated carbapenem‑resistant A. baumannii (CRAB) isolates to determine their resistance profiles and the presence of specific β‑lactamases to inform CRAB surveillance upon hospital admission and regional empiric antibiotic therapies., Patients and Methods: The study was conducted at 4 hospitals in southern Poland between June and December 2022. Only health care-associated infections caused by A. baumannii were considered. A total of 82 CRAB isolates were included in the analysis. Species identification was performed by matrix‑assisted laser desorption / ionization time‑of‑flight mass spectrometry, antimicrobial susceptibility was determined phenotypically, and polymerase chain reactions were carried out to identify the resistance genes., Results: Depending on the hospital, the incidence of CRAB infections varied from 428.6 to 759.5 per 10 000 admissions in intensive care units (ICUs), and from 0.3 to 21 per 10 000 admissions in non‑ICUs. CRAB antibiotic susceptibility was the highest for cefiderocol (100%), colistin (96%), tigecycline (77%), gentamicin (51%), and ampicillin / sulbactam (36%). The most prevalent blaOXA genes were blaOXA‑66‑1 (95%) and blaOXA‑40 (71%), and additionally the extended‑spectrum β‑lactamase gene blaTEM‑1 (41%)., Conclusion: An unexpectedly high incidence of CRAB infections occurred in Polish hospitals. There is a need for effective CRAB prevention and control that includes effective hospital screening, national surveillance, and improved treatment options.

Objectives: To report trends in carbapenem resistance and difficult-to-treat resistance (DTR) among clinical isolates of Gram-negative priority pathogens collected by the ATLAS global surveillance program from 2018 to 2022., Methods: Reference broth microdilution testing was performed in a central laboratory for 79,214 Enterobacterales, 30,504 Pseudomonas aeruginosa, and 13,500 Acinetobacter baumannii-calcoaceticus complex isolates collected by a constant set of 157 medical centres in 49 countries in Asia Pacific (APAC), Europe (EUR), Latin America (LATAM), Middle East-Africa (MEA), and North America (NA) regions. MICs were interpreted by 2023 CLSI M100 breakpoints. β-lactamase genes were identified for meropenem-nonsusceptible (MIC ≥2 mg/L) Enterobacterales isolates., Results: Carbapenem-resistant Enterobacterales (CRE) detection increased (P < 0.05) in APAC, EUR, LATAM, and MEA regions and decreased in NA, while annual DTR percentages increased in all five regions. Carbapenem-resistant P. aeruginosa (CRPA; decreased in MEA region) and carbapenem-resistant A. baumannii-calcoaceticus complex (CRAB; decreased in MEA region and increased in EUR) remained relatively stable over time in all regions, although notably, annual percentages of CRAB and DTR A. baumannii-calcoaceticus complex isolates were consistently >25 percentage points lower in NA than in other regions. For all regions except NA, the majority of changes in CRE percentages could be attributed to hospital-acquired infections. Among meropenem-nonsusceptible Enterobacterales, KPC was the most frequent carbapenemase in NA and EUR each year. NDM was the most prevalent carbapenemase detected in 2022 in other global regions., Conclusion: CRE, CRPA, CRAB, and DTR rates vary among global regions over time highlighting the need for continuing surveillance to inform treatment strategies and antimicrobial stewardship., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Objectives: This study aimed to determine the in vitro efficacy of cefiderocol in carbapenem-resistant Acinetobacter baumannii (CRAB) isolates and evaluate the disk-diffusion (DD) method as an alternative method to broth-microdilution (BMD)., Methods: Totally 89 CRAB isolates were included. Cluster analysis was determined by Pulsed-Field Gel Electrophoresis (PFGE). Resistance genes; bla OXA-51 , bla OXA-23 , bla OXA-24 , bla OXA-58, bla PER-1 , bla NDM , bla IMP and mcr-1 were screened. Cefiderocol susceptibility testing was performed by both DD and BMD. Interpretation was made according to EUCAST and CLSI. Categorical agreement (CA), minor errors (mEs), major errors (MEs), and very major errors (VMEs) were determined., Results: PFGE revealed 5 distinct pulsotypes; 86 of the isolates were extensively drug-resistant (XDR). All the isolates were negative for bla NDM , bla IMP , mcr-1, while positive for bla OXA-58 and bla OXA51 . bla PER-1 was positive for 33.7%; bla OXA-23 for 74.2%; bla OXA-24 for 12.3%. According to CLSI, the MEs rate was 1.85%, mEs was 7.86% and there were no VMEs. According to EUCAST, MEs rate was 3.70%, there were no mEs and VMEs. CA was 91% for CLSI and 97.8% for EUCAST. MICs of cefiderocol against A. baumannii isolates ranged from 0.06 to > 128 mg/L, with MIC50 and MIC90 values of 0.5 and > 128 mg/L, respectively., Conclusions: Cefiderocol susceptibility was 60.7% in CRAB isolates. MIC50, MIC90 of bla PER-1 positive and bla PER-1 negative groups were > 128/>128 and 0.25/>128 mg/L. A correlation between the presence of bla PER-1 and cefiderocol resistance was observed (p < 0.0001). Among colistin-resistant isolates, the presence of bla PER-1 was 47.1% and 75% of them were resistant to cefiderocol respectively., (© 2024. The Author(s).)

Objective: To evaluate the virulence levels of carbapenem-resistant Acinetobacter baumannii ST191, ST195, and ST208, and to analyze the differences in virulence factors among these epidemic clones. Methods: The study involved the genomic sequencing of 233 Acinetobacter baumannii strains that were isolated from the Fifth Medical Center of the Chinese People's Liberation Army General Hospital (North Hospital) between 2011 and 2019. The genomic data was cross-referenced with the Virulence Factor Database (VFDB) to examine the presence of virulence genes in the strains. Furthermore, a Galleria mellonella infection survival model was used to evaluate the virulence levels of the strains, and the association between virulence levels and virulence genes was analyzed. Results: The study included 38 strains of the ST191 clone, 104 strains of the ST195 clone, and 91 strains of the ST208 clone. In the Galleria mellonella infection survival experiment, the average mortality rate for ST191 was 23.0%, with 3 (7.9%) highly virulent strains. For ST195, the average mortality rate was 53.0%, with 34 (32.7%) highly virulent strains. For ST208, the average mortality rate was 47.0%, with 20 (21.9%) highly virulent strains. There was a significant statistical difference in mortality rates between ST191 and ST195 ( χ 2 =13.9, P <0.001) as well as between ST191 and ST208 ( χ 2 =15.2, P <0.001). A comparison of the strains with the VFDB revealed significant differences in the virulence genes carried by the clones. Specifically, the type Ⅵ secretion system-related genes ( clpV/tssH, hcp/tssD, tagX, tssA, tssB, tssC, tssE, tssF, tssG, tssK, ssL, tssM ) and the sugar transferase gene ACICU&#95;RS00475 were found to be universally absent in ST191 strains (0%) while being prevalent in ST195 (100.0%) and ST208 (>82.0%) strains. Statistical analysis revealed an association between the mortality rate of the clones and the presence of virulence genes( clpV/tssH P <0.001, hcp/tssD P =0.001, tagX P <0.001, tssA P <0.001, tssB P =0.001, tssC P =0.001, tssE P= 0.001, tssF P =0.001, tssG P <0.001, tssK P <0.001, tssL P <0.001, tssM P =0.001, ACICU&#95;RS00475 P =0.001). Conclusion: Among the carbapenem-resistant epidemic clones of Acinetobacter baumannii , the ST191 clone shows lower mortality rates in Galleria mellonella , possibly because of the lack of type Ⅵ secretion system and sugar transferase genes.

Brazil is recognized for its biodiversity and the genetic variability of its organisms. This genetic variability becomes even more valuable when it is properly documented and accessible. Understanding bacterial diversity through molecular characterization is necessary as it can improve patient treatment, reduce the length of hospital stays and the selection of resistant bacteria, and generate data for health and epidemiological surveillance. In this sense, in this study, we aimed to understand the biodiversity and molecular epidemiology of carbapenem-resistant bacteria in clinical samples recovered in the state of Rondônia, located in the Southwest Amazon region. Retrospective data from the Central Public Health Laboratories (LACEN/RO) between 2018 and 2021 were analysed using the Laboratory Environment Manager Platform (GAL). Seventy-two species with carbapenem resistance profiles were identified, of which 25 species carried at least one gene encoding carbapenemases of classes A (bla KPC -like), B (bla NDM -like, bla SPM -like or bla VIM -like) and D (bla OXA-23 -like, bla OXA-24 -like, bla OXA-48 -like, bla OXA-58 -like or bla OXA-143 -like), among which we will highlight Klebsiella pneumoniae, Pseudomonas aeruginosa, Acinetobacter baumannii, Serratia marcescens, and Providencia spp. With these results, we hope to contribute to the field by providing epidemiological molecular data for state surveillance on bacterial resistance and assisting in public policy decision-making., (© 2024. The Author(s).)

Objectives: To study the distribution, drug resistance, and biofilm characteristics of carbapenem-resistant Acinetobacter baumannii (CRAB) isolated from hospitalized children, providing a reference for the prevention and treatment of CRAB infections in hospitalized children., Methods: Forty-eight CRAB strains isolated from January 2019 to December 2022 were classified into epidemic and sporadic strains using repetitive extragenic palindromic sequence-based polymerase chain reaction. The drug resistance, biofilm phenotypes, and gene carriage of these two types of strains were compared., Results: Both the 22 epidemic strains and the 26 sporadic strains were producers of Class D carbapenemases or extended-spectrum β-lactamases with downregulated outer membrane porins, harboring the VIM , OXA-23 , and OXA-51 genes. The biofilm formation capability of the sporadic strains was stronger than that of the epidemic strains ( P <0.05). Genes related to biofilm formation, including Bap , bfs , OmpA , CsuE , and intI1 , were detected in both epidemic and sporadic strains, with a higher detection rate of the intI1 gene in epidemic strains ( P <0.05)., Conclusions: CRAB strains are colonized in the hospital, with sporadic strains having a stronger ability to form biofilms, suggesting the potential for forming new clonal transmissions in the hospital. Continuous monitoring of the epidemic trends of CRAB and early warning of the distribution of epidemic strains are necessary to reduce the risk of CRAB infections in hospitalized children.

Acinetobacter baumannii (Ab) has increasingly been identified as a cause of hospital-acquired infections and epidemics. The rise of carbapenem-resistant Acinetobacter baumannii (CRAB) poses significant challenges in treatment. Nosocomial outbreaks linked to CRAΒ A. baumannii strains have been reported worldwide, including in Greece. This study aimed to analyze the molecular epidemiology trends of multidrug-resistant A. baumannii isolates in a tertiary hospital in Athens, Greece. A total of 43 clinical isolates of extensively drug-resistant (XDRAB), pan-drug-resistant (PDRAB), and CRAB were collected from patients suffering from blood infection, hospitalized between 2016 and 2020 at the internal medicine clinics and the ICU. A.baumannii isolates underwent testing for Ambler class B and D carbapenemases and the detection of IS Aba1 , and were typed, initially, using pulsed-field gel electrophoresis, and, subsequently, using sequence-based typing and multiplex PCR to determine European Clone lineages. The bla OXA-23 gene accompanied by IS Aba 1 was prevalent in nearly all A. baumannii isolates, except for one carrying bla OXA-58 . The intrinsic bla OXA-51-like gene was found in all isolates. No Ambler class B carbapenemases (VIM, NDM) were detected. Isolates were grouped into four PF-clusters and no one-cluster spread was documented, consistent with the absence of outbreak. The study indicated that XDR/PDR-CRAB isolates predominantly produce OXA-23 carbapenemase and belong to European Clone II. Further research is needed to understand the distribution of resistant bacteria and develop effective prevention and control strategies.

The aim of the study was to evaluate the relationship between carbapenem-resistant Acinetobacter baumannii isolates carrying oxacillinase-type carbapenemase genes with "international high-risk clones" (IC I, II, and III) by different molecular epidemiological methods and to statistically compare the concordance and discrimination power of the methods. Carbapenem-resistant and moderately susceptible A.baumannii isolates from non-repeating blood cultures of 72 patients were included in the study. The presence of "blaOXA-23 , blaOXA-24 , blaOXA-51 ve blaOXA-58 " genes within OXA-type carbapenemases was detected by polymerase chain reaction (PCR) method and confirmed by DNA sequence analysis. Pulsed f ield gel electrophoresis (PFGE), multilocus sequence typing (MLST) and matrix-assisted laser desorption/ ionization time- of-flight mass spectrometry (MALDI-TOF MS) analyses were performed to evaluate the clonal relations of IC I, II and III clones together with clinical isolates. In the statistical comparison of the methods, discrimination power was evaluated by Simpson index of diversity (SID) and concordance by "Wallace coefficient". All of the isolates were found to carry blaOXA-23 and blaOXA-51 genes. As a result of the bioinformatic analysis of the four isolates selected for sequence analysis; blaOXA-23 and blaOXA-51 genes were detected in the selected isolates, and the analysis of two isolates carrying blaOXA-51 gene showed 99% similarity with blaOXA-92 gene. The isolates were clustered into five pulsotypes (A, B, C, D and E) according to ≥ 85% similarity coefficient by PFGE. The isolates and RUH 875, RUH 134, LUH 5875 strains belonging to high-risk clones ICI, ICII and ICIII, respectively, were divided into five main groups [A (n= 58), B (n= 8), C (n= 4), D (n= 4) and E (n= 1)] and 10 subgroups (A1, A2, A4, A5, A6, A9, B1, B4, C3, D1) by PFGE. IC clone III (E1) and seven strains showed singleton PFGE profiles (A3, A7, A8, B2, B3, C1, C2). ICII was found in A5 subtype, ICI in C1 subtype and ICIII in E1 subtype. By PFGE subtype groups, 18 pulsotypes were determined and ST1, ST2, ST81, ST157 and ST604 sequence types were found in 20 isolates randomly selected from pulsotypes according to MLST Pasteur scheme (cpn60, fusA, gltA, pyrG, recA, rplB, rpoB). Principal component analysis (PCA) of the spectra of 72 A. baumannii isolates and ICI, ICII and ICIII clones was performed by MALDI-TOF MS. In PCA analysis, the cluster distance level was defined as 1.5 and the isolates were divided into three clusters. IC clone I, II and III together with 70 clinical isolates were grouped in one cluster, while two clinical isolates (AB083 and AB0115) formed singleton clusters. There was no significant agreement between MALDI-TOF MS; MLST and PFGE data according to Wallace coefficient. It was found that PFGE method gave significant results in terms of discrimination power with SID coefficient, MALDI-TOF MS PCA analysis had the lowest discrimination power value, and the Wallace coefficient result of PFGE and MLST was concordant. In conclusion, MALDI-TOF MS may not function as a gold standard method like PFGE and MLST for epidemiological analysis in A.baumannii species and the epidemiological typing protocols used for MALDI-TOF MS need to be improved and developed.

Importance: Carbapenem-resistant Acinetobacter baumannii are of increasing public health importance, as they are resistant to last-line antibiotics. International clones with well-characterized resistance genes dominate globally; however, locally, other lineages with different properties may be of importance to consider. This study investigated isolates from a broad geographic origin from 114 hospitals in 47 countries and from five world regions ensuring the greatest possible diversity in an organism known for its propensity for clonal epidemic spread and reflecting the current global epidemiology of carbapenem-resistant A. baumannii . In Latin America, a lineage different from other geographic regions circulates, with a different resistance gene profile. This knowledge is important to adjust local infection prevention measures. In a global world with migration and increasing use of antimicrobials, multidrug-resistant bacteria will continue to adapt and challenge our healthcare systems worldwide., Competing Interests: H.S. has received grants or research support from the BMBF, the German Center for Infection Research (DZIF), and Accelerate Diagnostics and has been a consultant for Debiopharm, Eumedica, Gilead, MSD, and Shionogi. All others have no conflicts of interest to declare.

Objectives: Among the high-risk clones of Acinetobacter baumannii, called international clones (ICs), IC2 represents the main lineage causing outbreaks worldwide. Despite the successful global spread of IC2, the occurrence of IC2 is rarely reported in Latin America. Here, we aimed to evaluate the susceptibility and genetic relatedness of isolates from a nosocomial outbreak in Rio de Janeiro/Brazil (2022) and perform genomic epidemiology analyses of the available genomes of A. baumannii., Methods: Sixteen strains of A. baumannii were subjected to antimicrobial susceptibility tests and genome sequencing. These genomes were compared phylogenetically with other IC2 genomes from the NCBI database, and virulence and antibiotic resistance genes were searched., Results: The 16 strains represented carbapenem-resistant A. baumannii (CRAB) with an extensively drug-resistant profile. In silico analysis established the relationship between the Brazilian CRAB genomes and IC2/ST2 genomes in the world. The Brazilian strains belonged to three sub-lineages, associated with genomes from countries in Europe, North America, and Asia. These sub-lineages presented three distinct capsules, KL7, KL9, and KL56. The Brazilian strains were characterised by the co-presence of blaOXA-23 and blaOXA-66, in addition to the genes APH(6), APH(3"), ANT(3"), AAC(6'), armA, and the efflux pumps adeABC and adeIJK. A large set of virulence genes was also identified: adeFGH/efflux pump; the siderophores barAB, basABCDFGHIJ, and bauBCDEF; lpxABCDLM/capsule; tssABCDEFGIKLM/T6SS; and pgaABCD/biofilm., Conclusion: Widespread extensively drug-resistant CRAB IC2/ST2 is currently causing outbreaks in clinical settings in southeastern Brazil. This is due to at least three sub-lineages characterised by an enormous apparatus of virulence and resistance to antibiotics, both intrinsic and mobile., (Copyright © 2023 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Background: The rapid emergence of carbapenem resistant Acinetobacter baumannii (CRAB) has resulted in an alarming situation worldwide. Realizing the dearth of literature on susceptibility of CRAB in genetic context in the developing region, this study was performed to determine the susceptibility profile against standard drugs/combinations and the association of in-vitro drug synergy with the prevalent molecular determinants., Methods and Findings: A total of 356 clinical isolates of A. baumannii were studied. Confirmation of the isolates was done by amplifying recA and ITS region genes. Susceptibility against standard drugs was tested by Kirby Bauer disc diffusion. Minimum inhibitory concentration (MIC), MIC 50 and MIC 90 values against imipenem, meropenem, doripenem, ampicillin/sulbactam, minocycline, amikacin, polymyxin B, colistin and tigecycline was tested as per guidelines. Genes encoding enzymes classes A ( bla GES , bla IMI/NMC-A , bla SME , bla KPC ), B ( bla IMP , bla VIM , bla NDM ) and D ( bla OXA-51, bla OXA-23 and bla OXA-58 ) were detected by multiplex polymerase chain reaction. Synergy against meropenem-sulbactam and meropenem-colistin combinations was done by checkerboard MIC method. Correlation of drug synergy and carbapenemase encoding genes was statistically analyzed., Results: Of the total, resistance above 90% was noted against gentamicin, ciprofloxacin, levofloxacin, ceftazidime, cefepime, ceftriaxone, cotrimoxazole and piperacillin/tazobactam. By MIC, resistance rates from highest to lowest was seen against imipenem 89.04% (n=317), amikacin 80.33% (n=286), meropenem 79.49% (n=283), doripenem 77.80% (n=277), ampicillin/sulbactam 71.62% (n=255), tigecycline 55.61% (n=198), minocycline 14.04% (n=50), polymyxin B 10.11% (n=36), and colistin 2.52% (n=9). CRAB was 317 (89.04%), 81.46% (n=290) were multidrug resistant and 13.48% (n=48) were extensively drug resistant. All the CRAB isolates harboured bla OXA-51 gene (100%) and 94% (n=298) bla OXA-23 gene. The bla IMP gene was most prevalent 70.03% (n=222) followed by bla NDM, 59.62% (n=189). Majority (87.69%, 278) were co-producers of classes D and B carbapenemases, bla OXA-23 with bla IMP and bla NDM being the commonest. Synergy with meropenem-sulbactam and meropenem-colistin was 47% and 57% respectively. Reduced synergy ( p = <0.0001) was noted for those harbouring bla OXA-51 +bla OXA-23 with bla NDM gene alone or co-producers., Conclusion: Presence of bla NDM gene was a significant cause of synergy loss in meropenem-sulbactam and meropenem-colistin. In bla NDM endemic regions, tigecycline, minocycline and polymyxins could be viable options against CRAB isolates with more than one carbapenemase encoding genes., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Sharma, Banerjee, Yadav and Kumar.)

Objective: To explore the carrying status and homology of carbapenem resistant Acinetobacter baumannii (CRAB) in our hospital., Methods: From January 2015 to December 2017, 52 strains of acinetobacter baumannii isolated from the bacteria room of the clinical laboratory of Baogang hospital in Inner Mongolia were selected as the research object. K-B disk diffusion method and Vitek-2 were used to determine the drug sensitivity of Acinetobacter baumannii. The drug resistance gene was detected by polymerase chain reaction (PCR) and its homology was analyzed by pulsed field gel electrophoresis (PFGE)., Results: Except for Cefoperazone/sulbactam, other antibiotics were resistant to ab. The detection rate of drug resistance gene class C β-lactamases (ADC) was 100%, and the higher detection rates of other drug resistance genes were class D β-lactamases (OXA)-51 (36 strains, 90.0%),disinfectant gene qacE△1-sull (32 strains, 80.0%), and klebsiella pneumoniae carbapenemase (KPC) gene was not detected. 2-8 drug resistance genes were detected in each CRAB strain, and the strains with 6 drug resistance genes were the most (15 strains, 37.5%); Among the detected drug-resistant gene combinations, ADC+OXA-23 + OXA-51 gene was detected at the same time (29 strains, 72.5%), followed by ADC+ intl1 + qacE △ 1-sull gene (26 strains, 65.0%), ADC + qacE △ 1-sull + ant (3 '') -i gene (19 strains, 47.5%), and 11 strains (27.5%). There were 19 different types in PFGE homology test, each type was 1-9 strains, including 9 strains of A5 type and 8 strains of A18 type, mainly from intensive care unit., Conclusion: CRAB in the hospital is highly resistant to common clinical antibiotics. OXA-23 and OXA-51 genes are most likely to be the main factors causing drug resistance of Acinetobacter baumannii in the hospital. Homology analysis showed that there was CRAB nosocomial infection transmission in different wards of the hospital., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Guo, Huang and Li.)

The aim of this study was to investigate and compare the molecular epidemiology and carbapenem resistance determinants in clinical Acinetobacter baumannii isolates collected during four multicentre surveillance studies conducted by the Paul-Ehrlich-Society for Infection Therapy. Isolates were collected prospectively from hospital in-patients at 17 medical centres in Germany over four periods of three- to six-months starting in October of each of 2010, 2013, 2016 and 2019. Species identification was performed by MALDI-TOF, gyrB multiplex polymerase chain reaction (PCR), and detection of the intrinsic bla OXA-51-like gene. Minimum inhibitory concentrations were determined by broth microdilution. The prevalence of carbapenemase-encoding genes was investigated by OXA-multiplex PCR and whole-genome sequencing. Molecular epidemiology was examined by rep-PCR and core-genome multi-locus sequence typing. A total of 302 A. baumannii isolates were collected. Resistance to imipenem and/or meropenem was detected in 58 isolates (19.2%) from 14 centres. The proportion of carbapenem-resistant isolates increased from 21.3% in 2010 to 33.3% in 2013, and then decreased to 13.8% in 2016 and 12.3% in 2019. Forty-six of these isolates were associated with the international clonal lineage IC2 and five with IC1. The most prevalent carbapenemase gene detected was bla OXA-23-like (n=51). Further carbapenem-resistance determinants were bla OXA-40-like (n=1), bla OXA-58-like (n=3) and bla NDM-1 (n=2). In one isolate, ISAba1 was detected upstream of bla OXA-51-like . In conclusion, IC2 was the most prevalent clonal lineage detected in this study. Interestingly, in Germany, carbapenem resistance seems to have decreased in A. baumannii between 2013 and 2019., Competing Interests: Declaration of Competing Interest M.K. was an acting partner of Antiinfectives Intelligence GmbH, a research organisation providing services to pharmaceutical companies. E.W. is the head of the laboratory at Antiinfectives Intelligence GmbH and the novel acting partner. H.S. has received grants or research support from the German Center for Infection Research (DZIF), and has been a consultant for Debiopharm, Eumedica, Gilead, MSD, and Shionogi. Other authors: none to declare., (Copyright © 2022. Published by Elsevier Ltd.)

Aim: Carbapenem resistant Acinetobacter baumannii have limited treatment options and a propensity to cause hospital outbreaks. In recent years an increase in their detection has been observed in New Zealand. This study aimed to describe the molecular epidemiology of these isolates., Method: This study utilised carbapenem resistant A. baumannii complex isolates identified across New Zealand between January 2010 to April 2018. Whole genome sequence analysis and associated demographic information was used to contextualise local isolates within the global epidemiology and establish the relationship between isolates., Results: Thirty-three carbapenem resistant A. baumannii complex isolates (31 A. baumannii sensu stricto) were identified. Twenty-four (73%) were from January 2015 onwards. Twenty-four (73%) had an identifiable epidemiological link to overseas hospitalisation. Twenty-three (74%) of 31 A. baumannii sensu stricto were sequence type (ST) 2 (Pasteur scheme). Phylogenetic analysis identified three ST2 clusters. The largest cluster, of 12 isolates, was from 2015 onwards; with nine (75%) associated with recent hospitalisation in Fiji or Samoa., Conclusion: Increasing numbers of carbapenem resistant A. baumannii are being identified in New Zealand. Our data show that this is in large part associated with transnational spread of a single A. baumannii sensu stricto ST 2 strain between Fiji, Samoa and New Zealand., Competing Interests: Nil., (© PMA.)

Resistance-nodulation-division-type efflux system AdeABC plays an important role in carbapenem resistance among Acinetobacter baumannii. However, a knowledge gap is observed regarding the role of its regulator AdeRS in carbapenem-resistant A. baumannii (CRAB). This study effectively combines microbiological analysis with an in-silico structural approach to understand the contribution of AdeRS among CRAB ( n  = 38). Additionally, molecular docking was performed for the first time to study the interaction of FDA-approved carbapenems and pump inhibitor PAβN with the open and closed structure of AdeB at the three binding sites (periplasmic, proximal, distal). It was observed that open conformation of AdeB facilitates the binding of carbapenems and PAβN at entrance and proximal sites compared to the closed conformation. PAβN was found to block carbapenem interacting residues in AdeB, establishing its role as a competitive inhibitor of AdeB substrates. Overexpression of AdeABC was detected by q-RT-PCR among 29% of CRABs, and several mutations within AdeS (GLY186VAL, SER188PHE, GLU121LYS, VAL255ILE) and AdeR (VAL120ILE, ALA136VAL) were detected by sequencing. The sequence and structure-based study of AdeRS was performed to analyze the probable effect of these mutations on regulation of the two-component system (TCS), especially, utilizing its three-dimensional structure. AdeS mutations inhibited the transfer of a phosphate group to AdeR, preventing the binding of AdeR to the intercistronic region, leading to overexpression of AdeABC. The elucidation of the role of mutations in AdeRS improves our understanding of TCS-based regulation. Identification of the key residues of AdeB interacting with carbapenems and PAβN may help in future designing of novel inhibitors. IMPORTANCE AdeABC is an important efflux pump in A. baumannii that plays a role in resistance toward different antibiotics including the "last resort" antibiotic, carbapenem. This pump is regulated by a two-component system, AdeRS. To understand the binding of carbapenems with AdeABC and pump inhibition by PAβN, we analyzed for the first time the possible atomic level interactions of carbapenems and PAβN with AdeB. In the current study, AdeRS-associated novel mutations in clinical A. baumannii are reported for the first time, and a sequence-structure based in-silico approach was used to interpret their role in AdeABC overexpression, leading to carbapenem resistance. None of the previous studies had undertaken both these aspects simultaneously. This study analyzes the open and closed conformation of AdeB, their binding with carbapenems, and key residues involved in it. This helps in visualizing the plausible atomic level causes of pump inhibition driving the discovery of novel inhibitors.

The gram-negative strain Acinetobacter baumannii is a cocobacillus, non-motile and aerobic organism that is often found in nosocomial infections. Many institutions worldwide such as WHO are grappling with antibiotic resistance A. baumannii. Therefore, in recent years, there have been many studies in the literature about antibiotic resistance mechanisms. We studied the specificity of carbapenems for CarO, an outer membrane protein associated with imipenem-resistance that was strongly related to a decrease in CarO expression level or changes in protein structure. The specificity of five different carbapenems, imipenem, biapenem, ertapenem, faropenem, and meropenem, against the A. baumannii ATCC-17978 CarO protein, as well as the specificity of imipenem for five different types Type-1, Type-2, Type-3, Type-4, and ATCC-17978 CarO protein, were investigated using computational methods. In this study, homology modeling, molecular docking, membrane-protein complex building, and 800 ns long MD simulation methods were followed. The interactions of imipenem with the extracellular region of five different forms of CarO protein were investigated in this study, as well as five different antibiotic binding profiles to the model organism ATCC-17978 CarO protein. The mechanism of CarO influx has been revealed with this study at the molecular level and this data is intended to be used in future research, mutagenesis, and clinical trials., Competing Interests: Declaration of competing interest The authors declare that they have no conflicts of interest., (Copyright © 2022 Institut Pasteur. Published by Elsevier Masson SAS. All rights reserved.)

Acinetobacter baumannii has become a major healthcare threat that causes nosocomial infections, especially in critically ill patients. The spread of carbapenem-resistant A. baumannii (CRAB) strains has long been a clinical concern. It is important to study the epidemiology and virulence characteristics of different CRAB isolates in order to tailor infection prevention and antibiotic prescribing. In this study, a total of 71 CRAB isolates were collected in the hospital, and clinical characteristics of infections were analyzed. The genomic characteristics and phylogenetic relationships were elucidated based on genome sequencing and analysis. The isolates were assigned to three sequence types (STs, Pasteur) and nine capsular polysaccharide (KL) types, among which ST2/KL22 was the most prevalent CRAB in the hospital. Even though all the ST2/KL22 isolates contained the same reported virulence genes, one specific clade of ST2/KL22 showed more pathogenic in mouse infection model. Complete genomic analysis revealed differences at the oprD locus between the low- and high-virulent isolates. More specifically, a premature stop codon in the low-virulence strains resulted in truncated OprD expression. By evaluating pathogenicity in C57BL/6 J mice, knock-out of oprD in high-virulent isolate resulted in virulence attenuation, and complementing the avirulent strain with full-length oprD from high-virulent isolate enhanced virulence of the former. The oprD gene may be associated with the enhanced virulence of the specific ST2/KL22 clone, which provides a potential molecular marker for screening the hypervirulent A. baumannii strains.

The widespread of carbapenem-resistant Acinetobacter baumannii (CRAB) is of great concern in clinical settings worldwide. It is urgent to develop new therapeutic agents against this pathogen. This study aimed to evaluate the therapeutic potentials of compound 62520, which has been previously identified as an inhibitor of the ompA promoter activity of A. baumannii , against CRAB isolates, both in vitro and in vivo. Compound 62520 was found to inhibit the ompA expression and biofilm formation in A. baumannii ATCC 17978 at sub-inhibitory concentrations in a dose-dependent manner. These inhibitory properties were also observed in clinical CRAB isolates belonging to sequence type (ST) 191. Additionally, compound 62520 exhibited a bacteriostatic activity against clinical clonal complex (CC) 208 CRAB isolates, including ST191, and ESKAPE pathogens. This bacteriostatic activity was not different between STs of CRAB isolates. Bacterial clearance was observed in mice infected with bioimaging A. baumannii strain 24 h after treatment with compound 62520. Compound 62520 was shown to significantly increase the survival rates of both immunocompetent and neutropenic mice infected with A. baumannii ATCC 17978. This compound also increased the survival rates of mice infected with clinical CRAB isolate. These results suggest that compound 62520 is a promising scaffold to develop a novel therapeutic agent against CRAB infections.

Aims: Data on antimicrobial resistance (AMR) in the paediatric patient population are scarce. This study assessed the AMR rates and phenotype distribution of Gram-negative isolates in paediatric patients in Europe from 2004-2012 and 2013-2018., Methods: Isolates that were collected were stratified by age groups (< 1, 1-5, 6-12, and 13-17 years) and regions (North-Western, Eastern and Southern Europe). Minimal inhibitory concentrations (broth microdilution) were interpreted according to European Committee on Antimicrobial Susceptibility Testing guidelines. Resistance rates and phenotype prevalence were identified for Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Haemophilus influenzae., Results: In the overall paediatric patient population (0-17 years), extended-spectrum beta-lactamase (ESBL) production significantly decreased (from 20.7% to 15.4%, P < 0.0001) in Escherichia coli, whereas it increased for Klebsiella pneumoniae (from 35.0% to 39.2%, P = 0.015). Carbapenem resistance was highest for Acinetobacter baumannii (32.3%) compared with Klebsiella pneumoniae (4.7%) and Pseudomonas aeruginosa (12.4%) in 2013-2018, and rates were significantly increased relative to 2004-2012. There was no change in resistance to beta-lactam antimicrobials for Haemophilus influenzae. The lowest resistance rates for most organism groups were observed in North-Western Europe., Conclusions: The results revealed a significant increase in Klebsiella pneumoniae isolates with an ESBL and carbapenem-resistance phenotype as well as in carbapenem-resistant Acinetobacter baumannii and Pseudomonas aeruginosa from 2004-2012 to 2013-2018. Conversely, a decrease in ESBL E. coli was observed. Continued surveillance and awareness of resistance in these bacteria causing serious infections is crucial for improving treatment quality in paediatric patients., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

The expansion of specific carbapenem-resistant Acinetobacter baumannii (CRAB) clones is a global concern due to its therapeutic difficulty and epidemicity. To understand the prevalence of CRAB isolates in a Korean hospital, we investigated the epidemiological characteristics of 96 CRAB isolates between 2016 and 2018, including the sequence types (STs), antimicrobial susceptibility, and genetic background of resistance to carbapenems and aminoglycosides. Six STs were identified using the Oxford multilocus sequence typing scheme; ST191 (n = 8), ST208 (n = 12), ST229 (n = 11), and ST369 (n = 21) were previously identified clones in the study hospital, whereas gpi variants of ST208, ST451 (n = 34) and ST784 (n = 10), were emerging clones. ST208 isolates exhibited higher resistance rates to minocycline than other ST isolates, whereas ST369 isolates exhibited lower resistance rates to aminoglycosides and trimethoprim/sulfamethoxazole than other ST isolates. All CRAB isolates previously isolated in the study hospital carried ISAbaI-bla OXA-23 for carbapenem resistance, but 10 ST229 isolates carried only ISAbaI-bla OXA-51 . The carriage of armA was lower in ST369 isolates (38%) than in other ST isolates (≥83%). The frequency and diversity of aminoglycoside-modifying enzyme genes were decreased among the CRAB isolates between 2016 and 2018 compared with CRAB isolates between 2013 and 2015 at the study hospital. In conclusion, clonal complex 208 CRAB isolates are predominant in the study hospital. This study demonstrates the evolutionary change of CRAB isolates in the study hospital in relation to the emergence of new STs and selection of resistant genes., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Introduction. Outbreaks of carbapenem-resistant A. baumannii and A. nosocomialis have occurred worldwide in healthcare settings. Rapid and reliable molecular typing of bacterial isolates is vital for the effective surveillance of institutional outbreaks. The Pan-PCR and OXA-PCR assays are two multiplex PCR-based assays for the molecular typing of Acinetobacter species. Gap statement. However, few studies have investigated the discriminatory power of two multiplex PCR assays in in the genotyping of Acinetobacter species. Aim. We aimed to evaluate the efficacies of the Pan-PCR and OXA-PCR assays for molecular typing of A. baumannii and A. nosocomialis . Methodology. A total of 105 carbapenem-resistant A. baumannii isolates (CRABs) and 93 carbapenem-resistant A. nosocomialis isolates (CRANs) obtained from blood cultures were used for molecular typing by the Pan-PCR and OXA-PCR assays and two multilocus sequence typing (MLST) schemes. Results. The isolates were individually divided into 12 and 21 different sequence types via the Pasteur and Oxford MLST schemes, respectively. Additionally, these isolates were distinguished into 18 different types by the Pan-PCR and OXA-PCR assays. The results of the Pan-PCR and OXA-PCR assays distinguished CRABs and CRANs with a sensitivity of 98.13 % and a specificity of 100 %. Conclusion. The Pan-PCR and OXA-PCR assays are promising alternative methods for rapid molecular typing of CRABs and CRANs in a routine laboratory setting.

Acinetobacter baumannii (A. baumannii) represents a global threat owing to its ability to resist most of the currently available antimicrobial agents. Moreover, emergence of carbapenem resistant A. baumannii (CR-AB) isolates limits the available treatment options. Enzymatic degradation by variety of ß-lactamases, have been identified as the most common mechanism of carbapenem resistance in A. baumannii. The alarming increase in the prevalence of CR-AB necessitates continuous screening and molecular characterization to appreciate the problem. The present study was performed to assess the prevalence and characterize carbapenemases among 206 CR-AB isolated from various clinical specimens collected from different intensive care units at Kasr Al-Aini Hospital. All isolates were confirmed to be A. baumannii by detection of the blaOXA-51-like gene. Molecular screening of 13 common Ambler class bla carbapenemases genes in addition to insertion sequence (IS-1) upstream OXA-23 were performed by using four sets of multiplex PCR, followed by identification using gene sequencing technology. Among the investigated genes, the prevalence of blaOXA-23, and blaOXA-58 were 77.7%, and 1.9%, respectively. The ISAba1 was detected in 10% of the blaOXA-23 positive isolates. The prevalence of metallo-β-lactamases (MBLs) studied; blaNDM-1, blaSPM, blaVIM, blaSIM-1 were 11.7%, 6.3%, 0.5%, and 0.5% respectively. One of class A; bla KPC was detected in 10.7% of the investigated isolates. blaOXA-24/40, blaIMP, blaGES, blaVEB and blaGIM were not detected in any of the studied isolates. Moreover, 18.4% of the isolates have shown to harbor two or more of the screened bla genes. We concluded that the most prevalent type of ß-lactamases genes among CR-AB isolates collected from Egyptian patients were blaOXA-23 followed by blaNDM-1 and blaKPC., Competing Interests: The authors have declared that no competing interests exist.

Increasingly difficult treatment of multidrug-resistant (MDR) bacteria has become a global problem of the 21st century. Within a group of multiresistant bacteria, the Acinetobacter baumannii convincingly occupies the position at the top of the group designated as ESKAPE pathogens. In this study, 61 isolates of A. baumannii were recovered from different samples originating from various departments of the University Clinical Hospital Mostar during 2018. All of the isolates were identified using conventional phenotypic methods and the VITEK ® 2 Compact System, and were confirmed by MALDI-TOF mass spectrometry. The minimum inhibitory concentrations (MICs) were determined by the microbroth dilution method using MICRONAUT-S MDR MRGN-Screening and VITEK 2 Compact System. All strains were resistant to carbapenems and classified in eight different resistotypes according to their antibiotic resistance and macrorestriction pulsed-field gel electrophoresis profiles, with all belonging to IC II. One isolate displayed resistance to colistin (MIC ≥16 mg/L). The presence of bla OXA genes encoding OXA-type carbapenemases was investigated by multiplex PCR and the Eazyplex ® SuperBugAcineto system and showed 100% compatibility with the detection of acquired oxacillinases. Molecular characterization of the isolates tested in this study revealed the OXA-23- and OXA-40-like groups of acquired oxacillinases. Sequencing of two PCR products of the OXA-40-like group confirmed the presence of OXA-72. Survival assays with two selected isolates of A. baumannii encoding different mechanisms of carbapenem resistance revealed that one isolate was able to survive on a fragment of white laboratory coat during 90 days of monitoring. To the best of our knowledge, this is the first article to present the results of a comprehensive phenotypic, genotypic, and molecular analysis of A. baumannii isolates from the leading clinical hospital center in the southwestern part of Bosnia and Herzegovina, including data for the survival of this pathogen on the white laboratory coats used as compulsory medical clothing.

Successful treatment of Acinetobacter baumannii infections require early and appropriate antimicrobial therapy. One of the first steps in this process is understanding which β-lactamase (bla) alleles are present and in what combinations. Thus, we performed WGS on 98 carbapenem-resistant A. baumannii (CR Ab). In most isolates, an acquired bla OXA carbapenemase was found in addition to the intrinsic bla OXA allele. The most commonly found allele was bla OXA-23 (n = 78/98). In some isolates, bla OXA-23 was found in addition to other carbapenemase alleles: bla OXA-82 (n = 12/78), bla OXA-72 (n = 2/78) and bla OXA-24/40 (n = 1/78). Surprisingly, 20% of isolates carried carbapenemases not routinely assayed for by rapid molecular diagnostic platforms, i.e., bla OXA-82 and bla OXA-172 ; all had ISAba1 elements. In 8 CR Ab, bla OXA-82 or bla OXA-172 was the only carbapenemase. Both bla OXA-24/40 and its variant bla OXA-72 were each found in 6/98 isolates. The most prevalent ADC variants were bla ADC-30 (21%), bla ADC-162 (21%), and bla ADC-212 (26%). Complete combinations are reported., (Published by Elsevier Inc.)

Aims: Polymyxin-based combination therapy is often used to treat carbapenem-resistant Acinetobacter baumannii (A. baumannii) infections. Although sulbactam is intrinsically active against A. baumannii, few studies have investigated colistin/sulbactam combinations against carbapenem-resistant A. baumannii., Methods: Whole genome sequencing was undertaken on eight carbapenem-resistant (colistin-susceptible) isolates of A. baumannii from Chinese patients. Bacterial killing of colistin and sulbactam, alone and in combination, was examined with checkerboard (all isolates) and static and dynamic time-kill studies (three isolates). In the dynamic studies, antibiotics were administered in various clinically-relevant dosing regimens that mimicked patient pharmacokinetics., Results: The eight isolates consisted of ST195, ST191 and ST208 belonging to clonal complex 208, which is the most epidemic clonal type of A. baumannii globally. All isolates possessed Acinetobacter-derived cephalosporinase (ADC-61 or ADC-78) and seven of eight isolates contained the carbapenem-resistance gene bla OXA-23 . The colistin/sulbactam combination was synergistic against two of eight isolates in checkerboard studies. In time-kill studies, rapid bacterial killing of ca. 3-6 log 10 CFU/mL was observed with colistin monotherapy, followed by steady regrowth. Sulbactam monotherapy was generally ineffective. Substantially enhanced bacterial killing was observed with colistin/sulbactam combinations in both static and dynamic models, especially with the higher sulbactam concentration (2 g) and/or longer sulbactam infusion time (2 hours) in the dynamic model., Conclusions: This study was the first to use a pharmacokinetics/pharmacodynamics model to investigate synergistic activity of colistin/sulbactam combinations against A. baumannii. It showed that clinically-relevant dosing regimens of colistin combined with sulbactam may substantially improve bacterial killing of multidrug-resistant and carbapenem-resistant A. baumannii., (Copyright © 2021 Elsevier Ltd and International Society of Antimicrobial Chemotherapy. All rights reserved.)

The aim of this study was to determine the activity and synergistic mechanisms of resveratrol in combination with chlorhexidine against carbapenem-resistant Acinetobacter baumannii clinical isolates. The activity of resveratrol plus antimicrobial agents was determined by checkerboard and time-kill assay against carbapenem-resistant A. baumannii isolated from patients at the King Chulalongkorn Memorial Hospital, Bangkok, Thailand. Overexpression of efflux pumps that mediates chlorhexidine susceptibility was characterized by the ethidium bromide accumulation assay. The effect of resveratrol on the expression of efflux pump genes (adeB, adeJ, adeG abeS, and aceI) and the two-component regulators, adeR and adeS was determined by RT-qPCR. The combination of resveratrol and chlorhexidine resulted in strong synergistic and bactericidal activity against carbapenem-resistant A. baumannii. Up-regulation of adeB and aceI was induced by chlorhexidine. However, the addition of resveratrol increased chlorhexidine susceptibility with increased intracellular accumulation of ethidium bromide in A. baumannii indicating that resveratrol acts as an efflux pump inhibitor. Expression of adeB was significantly reduced in the combination of resveratrol with chlorhexidine indicating that resveratrol inhibits the AdeB efflux pump and restores chlorhexidine effect on A. baumannii. In conclusion, reduced adeB expression in A. baumannii was mediated by resveratrol suggesting that AdeB efflux pump inhibition contributes to the synergistic mechanism of resveratrol with chlorhexidine. Our finding highlights the potential importance of resveratrol in clinical applications., Competing Interests: The authors have declared that no competing interests exist

Dissemination of carbapenem-resistant Acinetobacter baumannii (CRAB) is mainly driven by the spread of clonal lineages. High frequencies of CRAB are reported in South America, and clonal complexes CC1, CC15, CC79 and CC25 are predominant. A total of 79 non-redundant CRAB recovered from 26 Brazilian hospitals were selected for antimicrobial susceptibility testing by microdilution and whole-genome sequencing (WGS). Multilocus sequence typing (MLST), acquired antimicrobial resistance genes and phylogeny based on high-quality SNPs were extracted from WGS data. XDR (86.1%), MDR (12.7%) and one PDR isolate from CC15 (1.3%) were identified. Colistin resistance was more frequent in CC25 isolates (P < 0.01). Prevalence of CC79 (n = 22; 27.8%) CC1 (n = 21; 26.6%), CC15 (n = 21; 26.6%) and CC25 (n = 12; 15.2%) was observed. Regarding carbapenem-hydrolysing class D β-lactamases (CHDLs), bla OXA-23 was frequently detected in CC1, CC15 and CC25 isolates, whereas bla OXA-72 was the most frequent CHDL in CC79 isolates [n = 12/22 (54.5%); P < 0.01]. High-quality SNP analysis correlated well with sequence type and revealed that CRAB clones are highly conversed and present some clone-specific resistance determinants. This study provides essential information to understand the antimicrobial resistance patterns of CRAB in Brazilian hospitals, where hyperendemic XDR-CRAB clones are disseminated. Phenotypic and genomic analysis of CRAB recovered from Brazilian hospitals revealed the predominance of XDR phenotype in the majority of international clonal complex CC79, CC1, CC15 and CC25. Dissemination of specific CRAB lineages in Brazil is suggested to be driven by their resistance determinants under antimicrobial selective pressure., (Copyright © 2020 Elsevier Ltd. All rights reserved.)