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Purpose: Today, Enterococcus species are one of the most frequent etiological agents in nosocomial infections. The aim of this study was to determine the susceptibility to antibiotics and the prevalence of high-level aminoglycoside resistance (HLAR) among Enterococcus strains. Materials and methods: The susceptibility of 85 isolates of Enterococcus (47 E. faecalis and 38 E. faecium) was determined using the disk diffusion method. The results were interpreted according to European Committee on Antimicrobial Suscepti-bility Testing (EUCAST) guidelines. PASW Statistics 17.0 was used for statistical analysis. Results: E. faecalis strains showed the highest susceptibility to ampicillin, tigecycline, vanco-mycin, imipenem, and linezolid and E. faecium to linezolid, tigecycline, and quinupristin/dalfopristin. Among all tested strains, high-level gentamicin resistance (HLGR) was found in 4% of E. faecalis and 8% of E. faecium strains, high-level strepto-mycin resistance (HLSR) in 45% and 42%, and HLAR in 50% and 32% of strains, respectively. HLGR was detected only in vancomycin-resistant Enterococcus (VRE)- strains (12%), while HLSR in 76.9% of VRE+ and 24% of VRE- strains, and HLAR in 23.1% of VRE+ and 64% of VRE- strains. The tested strains were also divided into two groups: HLSR+ and HLAR+. In both groups, statistically significant susceptibility differences (p<0.05) were found for ampicillin, imipenem and trimethoprim/sulfamethoxazole. The most frequent antibiotic resistance profile among E. faecalis strains was SR (resistance phenotype to strepto-mycin), and among E. faecium, AMPR, IMPR, CNR, SR, SXTR (ampicillin, imipenem, gentamicin, streptomycin, trimethoprim/sulfamethoxazole). Conclusions: This study showed the slowly increasing prevalence of HLAR and resistance to newer antibiotics (linezolid and tigecycline) among Enterococcus strains. It is necessary to search for new directions in the treatment of enterococcal infections. [ABSTRACT FROM AUTHOR]

The increasing prevalence of acquired carbapenemases in Gram - negative bacteria is one of the biggest problems in the prevention and therapy of infectious diseases. NDM (New Delhi Metallo-β-Lactamase) is a recently discovered enzyme which has the ability to hydrolyze all β-lactam antibiotics, except aztreonam. Making that scenario more worrisome is the fact that mobile fragments of DNA carrying blaNDM genes, also keeps a number of other genes encoding antibiotic resistance. NDM enzymes are currently present in different species of bacteria all over the world. NDM-producing bacteria are resistant to virtually all available antimicrobial agents except tigecycline, colistine and fosfomycine. [ABSTRACT FROM AUTHOR]

Introduction: Pseudomonas aeruginosa rods are increasingly causing serious infections in hospitalized patients. Particularly worrying is the increase of resistance to carbapenems antibiotics. Purpose: To evaluate susceptibility and the occurrence of genes (blaIMP and blaVIM) encoding resistance to carbapenems among Pseudomonas aeruginosa strains. Materials and methods: Studies were conducted for 50 strains of Pseudomonas aeruginosa (25 susceptible and 25 resistant to imipenem). Susceptibility to antibiotics was tested using the diffusion method and discs with antibiotics and / or strips with gradient concentrations of antibiotics. In the second phase we tested the ability of MBL production by all strains using the CD and DDST technique described in the literature. The next stage of the study was to evaluate the prevalence of carbapenems resistance genes. These studies were performed by PCR technique. Results: The studies found in both groups of Pseudomonas aeruginosa rods similar percentage of strains resistant to aminoglycoside antibiotics (from 72% to 88%) and ciprofloxacin (84%). There was no presence of the genes in any of the tested groups of Pseudomonas aeruginosa. Conclusion: Pseudomonas aeruginosa strains resistant to imipenem no posses blaIMP and blaVIM genes therefore their resistance was conditioned by the presence of other mechanisms. Antibiotics with high activity against Pseudomonas aeruginosa strains resistant to imipenem were polymyxin B (100% susceptible strains) and colistin (96% susceptible strains). [ABSTRACT FROM AUTHOR]

Background: The growing incidence of MDR Gram-negative bacteria is a rapidly emerging challenge in modern medicine., Objectives: We sought to establish the role of intrinsic drug-resistance regulators in combination with specific genetic mutations in 11 Enterobacter cloacae isolates obtained from a single patient within a 7 week period., Methods: The molecular characterization of eight carbapenem-resistant and three carbapenem-susceptible E. cloacae ST89 isolates included expression-level analysis and WGS. Quantitative PCR included: (i) chromosomal cephalosporinase gene (ampC); (ii) membrane permeability factor genes, e.g. ompF, ompC, acrA, acrB and tolC; and (iii) intrinsic regulatory genes, e.g. ramA, ampR, rob, marA and soxS, which confer reductions in antibiotic susceptibility., Results: In this study we describe the influence of the alterations in membrane permeability (ompF and ompC levels), intrinsic regulatory genes (ramA, marA, soxS) and intrinsic chromosomal cephalosporinase AmpC on reductions in carbapenem susceptibility of E. cloacae clinical isolates. Interestingly, only the first isolate possessed the acquired VIM-4 carbapenemase, which has been lost in subsequent isolates. The remaining XDR E. cloacae ST89 isolates presented complex carbapenem-resistance pathways, which included perturbations in permeability of bacterial membranes mediated by overexpression of ramA, encoding an AraC/XylS global regulator. Moreover, susceptible isolates differed significantly from other isolates in terms of marA down-regulation and soxS up-regulation., Conclusions: Molecular mechanisms of resistance among carbapenem-resistant E. cloacae included production of acquired VIM-4 carbapenemase, significant alterations in membrane permeability due to increased expression of ramA, encoding an AraC/XylS global regulator, and the overproduction of chromosomal AmpC cephalosporinase., (© The Author(s) 2020. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Klebsiella pneumoniae infections have always been an important problem in public health, but today, the increasing resistance of these bacteria to antibiotics due to β-lactamases production has renewed interest in K. pneumoniae infections. The aim of the study was to present a case of a neurosurgical patient with multidrug-resistant K. pneumoniae ST11 infection after craniectomy. Four K. pneumoniae isolates from various clinical materials of the patient undergone identification and susceptibility testing with the Vitek2 system. Tests for β-lactamases production were performed according to EUCAST guidelines. Strains were analyzed for bla genes responsible for β-lactamase production (bla TEM , bla SHV , bla CTX-M , bla VIM , bla IMP , bla NDM , bla KPC , bla OXA-48 ) using PCR. Moreover, the genetic relatedness of these isolates was determined by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). All tested strain presented multidrug resistance. The highest susceptibility was observed for imipenem, meropenem, and ertapenem. The strain isolated from the nervous system was ESBL-positive with bla SHV-11 , bla TEM-1 , and bla CTX-M-15 genes. Additionally, the strain from urine was bla KPC-3 -positive. Molecular typing revealed that all strains belonged to the same clone and identified two PFGE profiles. The analysis of MLST allelic profile showed that tested K. pneumoniae strains belonged to ST11. Identification of ST11 K. pneumoniae as etiological factor of infection unfavorably impacts on prognosis among neurosurgical patient after craniectomy.

The aim of this study was to investigate the synergy between ceftazidime-avibactam, ertapenem, fosfomycin, and tigecycline against carbapenemase-producing Klebsiella pneumoniae using the E test MIC:MIC (minimum inhibitory concentration) ratio synergy method. The results were interpreted using fractional inhibitory concentration index (FICI) to describe the effects of antimicrobial combinations in vitro . To assess the clinical significance of each antibiotic combination, the susceptible breakpoint index (SBPI) was calculated for each combination, and within each strain. The FICI method revealed that the most synergistic combinations against carbapenemase-producing K. pneumoniae were ceftazidime-avibactam with ertapenem and ceftazidime-avibactam with fosfomycin. This effect was demonstrated in 47% (9/19) of all tested clinical K. pneumoniae isolates. Considering the effects of all drug combinations in K. pneumoniae harboring bla KPC , bla NDM , and bla OXA-48 genes, we observed that the combination of ceftazidime-avibactam with fosfomycin was the most synergistic in New Delhi metallo-β-lactamase (NDM)-producing K. pneumoniae , and the combination of ceftazidime-avibactam with ertapenem was the most synergistic in K. pneumoniae carbapenemase (KPC)-producing K. pneumoniae . In addition, all tested combinations were synergistic against oxacillinase (OXA)-48-producing K. pneumoniae , except the combination of ceftazidime-avibactam with tigecycline. The SBPI index showed that ceftazidime-avibactam in combination with fosfomycin reduced the MIC to less than the susceptibility breakpoint among all tested carbapenemase-producing K. pneumoniae . Moreover, the combinations of ceftazidime-avibactam with ertapenem, and ceftazidime-avibactam with tigecycline were able to reduce the MIC to less than the susceptibility breakpoint in all KPC- and OXA-48-producing K. pneumoniae .

Purpose: Over the past years, an increase in resistance to aminoglycosides has been observed among Enterobacteriaceae rods. This resistance development reduces therapeutic options for infections caused by multidrug-resistance organisms. Because of the changing epidemiology of extended-spectrum β-lactamases (ESBLs) and resistance to aminoglycosides, we investigated the prevalence of the aac(3)-Ia, aac(6')-Ib, ant(4')-IIa, ant(2")-Ia, and aph(3")-Ib genes encoding aminoglycoside-modifying enzymes (AMEs) in ESBL-producing Escherichia coli as well as ESBL-non-producing isolates. To understand bacterial resistance to aminoglycoside antibiotics, we estimated resistance phenotypes and the presence of genes responsible for this resistance., Materials and Methods: The study was conducted on 44 E.coli strains originated from patients hospitalized at University Hospital of Bialystok. MIC values were obtained for gentamicin, amikacin, netilmicin, and tobramycin. Isolates were tested for the presence of the aac(3)-Ia, aac(6')-Ib, ant(4')-IIa, ant(2")-Ia, and aph(3")-Ib genes with the use of the PCR technique., Results: Resistance to aminoglycosides was found in 79.5% of the isolates. The highest percentages of resistance were observed for tobramycin (70,5%) and gentamicin (59%), followed by netilmicin (43.2%) and amikacin (11.4%). PCR assays revealed the presence of aac(6')-Ib among 26 (59.2%) strains, aph(3")-Ib among 16 (36.2%), aac(3)-Ia among 7 (15.9%), and ant(2")-Ia among 2 (4.6%) strains., Conclusions: The enzymatic resistance against aminoglycosides in northeastern Poland among clinical isolates of E. coli is predominantly caused by aac(6')-Ib and aph(3")-Ib. Amikacin may be used for therapy of infections caused by ESBL-producing E. coli, because of the low rates of resistance., (Copyright © 2017 Medical University of Bialystok. Published by Elsevier B.V. All rights reserved.)

Objectives: The growing incidence of multidrug-resistant (MDR) bacteria is an emerging challenge in modern medicine. The utility of carbapenems, which are considered 'last-line' agents, is being diminished by the growing incidence of various resistance mechanisms in Gram-negative bacteria. A molecular investigation was performed of an MDR carbapenem-resistant Citrobacter freundii of sequence type 8 (ST8) isolated from a hematology patient with acute myeloid leukemia., Methods: Multilocus sequence typing and analysis of the nucleotide sequence of the class I integron were performed using PCR and Sanger sequencing. Transformation of the resistance plasmid isolated following the alkaline lysis method was performed using chemically competent E. coli TOP10., Results: Molecular analysis of the carbapenem-resistant C. freundii revealed the presence of the VIM-4 isoenzyme located on the ∼55-kb transferable resistance plasmid. Interestingly, the bla VIM-4 gene was inserted into an unusual gene cassette containing a 169-bp direct repeat of the 3' segment of the bla VIM-4 gene., Conclusions: All unusual gene cassettes containing VIM-DR (direct repeat) described thus far have been harbored by non-fermenters, i.e., Acinetobacter and Pseudomonas, underscoring the importance of resistance determinant mobility, which may go even beyond genus, family, and order boundaries. Great efforts need to be taken to explore pathways of resistance to 'last-resort' antimicrobials, especially among clinically relevant pathogens., (Copyright © 2017 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

The effectiveness of carbapenems, considered as last-resort antimicrobials in severe infections, becomes compromised by bacterial resistance. The production of metallo-β-lactamases (MBLs) is the most significant threat to carbapenems activity among Pseudomonas aeruginosa. The aim of this study was to assess the presence and type of MBLs genes in carbapenem-resistant P. aeruginosa clinical strains, to identify the location of MBLs genes and to determine genetic relatedness between MBL-producers using pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). The first identified MBL-positive (with blaVIM genes) P. aeruginosa strains were isolated from patients hospitalized in the University Clinical Hospital of Bialystok in the period from September 2012 to December 2013. Variants of MBLs genes and variable integron regions were characterized by PCR and sequencing. PFGE was performed after digesting of bacterial genomes by XbaI enzyme. By MLST seven housekeeping genes were analyzed for the determination of sequence type (ST). Three strains carried the blaVIM-2 gene and one harbored the blaVIM-4 gene. The blaVIM genes resided within class 1 integrons. PCR mapping of integrons revealed the presence of four different cassette arrays. Genetic relatedness analysis by PFGE classified VIM-positive strains into four unrelated pulsotypes (A-D). MLST demonstrated the presence of four (ST 111, ST27, and ST17) different sequence type including one previously undescribed new type of ST 2342. Antimicrobial susceptibility testing showed that VIM-positive strains were resistant to carbapenems, cephalosporins, aminoglycosides, and quinolones, intermediate to aztreonam, and susceptible only to colistin. Integrons mapping, PFGE, and MLST results may point to different origin of these strains and independent introduction into hospitalized patients.

The growing incidence of multidrug-resistant (MDR) bacteria is an emerging challenge in modern medicine. The utility of carbapenems, considered "last-line" agents in therapy of infections caused by MDR pathogens, is being diminished by the growing incidence of various resistance mechanisms. Enterobacter cloacae have lately begun to emerge as an important pathogen prone to exhibiting multiple drug resistance. We aimed to investigate the molecular basis of carbapenem-resistance in 44 E. cloacae clinical strains resistant to at least one carbapenem, and 21 susceptible strains. Molecular investigation of 65 E. cloacae clinical strains was based on quantitative polymerase chain reaction (qPCR) allowing for amplification of ampC, ompF , and ompC transcripts, and analysis of nucleotide sequences of alleles included in MLST scheme. Co-operation of three distinct carbapenem resistance mechanisms has been reported-production of OXA-48 (5%), AmpC overproduction (97.7%), and alterations in outer membrane (OM) transcriptome balance. Carbapenem-resistant E. cloacae were characterized by (1.) downregulation of ompF gene (53.4%), which encodes protein with extensive transmembrane channels, and (2.) the polarization of OM transcriptome-balance (79.1%), which was sloped toward ompC gene, encoding proteins recently reported to possess restrictive transmembrane channels. Subpopulations of carbapenem-susceptible strains showed relatively high degrees of sequence diversity without predominant types. ST-89 clearly dominates among carbapenem-resistant strains (88.6%) suggesting clonal spread of resistant strains. The growing prevalence of pathogens resistant to all currently available antimicrobial agents heralds the potential risk of a future "post-antibiotic era." Great efforts need to be taken to explore the background of resistance to "last resort" antimicrobials.

The aim of the study was to evaluate the prevalence of OXA and other β-lactamase genes, antibiotic susceptibility, and the genetic relatedness among clinical isolates of P. aeruginosa resistant to carbapenems. The presence of bla- OXA genes was demonstrated in 48% of isolates belonging to four PFGE profiles. Most of them contained the blaOXA-2 gene (88.3%). Other blaOXA genes (Ps1310 with blaOXA-30 and Ps1309 with blaOXA-10) were found in only two isolates. The tested isolates also contained other β-lactamase genes such as blaVIM-2, blaVIM-4, blaSHV-5, and blaTEM-1. All isolates were susceptible only to colistin (100%).

The present study was conducted to investigate the prevalence of genes encoding resistance to aminoglycosides and fluoroquinolones among twenty-five Pseudomonas aeruginosa isolated between 2002 and 2009. In PCR, following genes were detected: ant(2″)-Ia in 9 (36.0%), aac(6')-Ib in 7 (28.0%), qnrB in 5 (20.0%), aph(3″)-Ib in 2 (8.0%) of isolates.

An increase in the antibiotic resistance among members of the Enterobacteriaceae family has been observed worldwide. Multidrug-resistant Gram-negative rods are increasingly reported. The treatment of infections caused by Escherichia coli and other Enterobacteriaceae has become an important clinical problem associated with reduced therapeutic possibilities. Antimicrobial carbapenems are considered the last line of defense against multidrug-resistant Gram-negative bacteria. Unfortunately, an increase of carbapenem resistance due to the production of Klebsiella pneumoniae carbapenemase (KPC) enzymes has been observed. In this study we describe the ability of E. coli to produce carbapenemase enzymes based on the results of the combination disc assay with boronic acid performed according to guidelines established by the European Community on Antimicrobial Susceptibility Testing (EUCAST) and the biochemical Carba NP test. Moreover, we evaluated the presence of genes responsible for the production of carbapenemases (bla KPC, bla VIM, bla IMP, bla OXA-48) and genes encoding other β-lactamases (bla SHV, bla TEM, bla CTX-M) among E. coli isolate. The tested isolate of E. coli that possessed the bla KPC-3 and bla TEM-34 genes was identified. The tested strain exhibited susceptibility to colistin (0.38 μg/mL) and tigecycline (1 μg/mL). This is the first detection of bla KPC-3 in an E. coli ST479 in Poland.

An increase in the antibiotic resistance among Enterococcus faecium strains has been observed worldwide. Moreover, this bacteria has the ability to produce several virulence factors and to form biofilm that plays an important role in human infections. This study was designed to compare the antibiotic resistance and the prevalence of genes encoding surface protein (esp), aggregation substance (as), surface adhesin (efaA), collagen adhesin (ace), gelatinase (gelE), and hialuronidase (hyl) between biofilm-producing and non-producing E. faecium strains. Therefore, ninety E. faecium clinical isolates were tested for biofilm-forming ability, and then were assigned to two groups: biofilm-positive (BIO(+), n =70) and biofilm-negative (BIO(-), n = 20). Comparison of these groups showed that BIO(+) isolates were resistant to β-lactams, whereas 10% of BIO(-) strains were susceptible to ampicillin (statistically significant difference, p = 0.007) and 5% to imipenem. Linezolid and tigecycline were the only antibiotics active against all tested isolates. Analysis of the virulence factors revealed that ace, efaA, and gelE genes occurred more frequently in BIO(-) strains (ace in 50% BIO(+) vs. 75% BIO(-); efaA 44.3% vs. 85%; gelE 2.9% vs. 15%, respectively), while hyl gene appeared more frequently in BIO(+) isolates (87.1% BIO(+) vs. 65% BIO(-)). These differences were significant (p < 0.05). We concluded that BIO(+) strains were more resistant to antibiotics than BIO(-) strains, but interestingly, BIO(-) isolates were characterized by possession of higher virulence capabilities.

We investigated the genetic similarities and expression of the MexAB-OprM efflux pump system in different clones of multiresistant Pseudomonas aeruginosa strains collected from 2002 to 2009 at two intensive care units (ICU). Regulatory and structural genes mexB, mexR, and mexA were found in 99%, 98%, and 94% of tested strains, respectively. The presence of class 1 integron was found in 90% of the strains, while class 2 integron in only one strain (Psa506). Class 3 integron was not found in any of the tested strains. Among the eleven clones identified, only two clones, I and D, exhibited higher levels of mexB gene expression than the other clones. Clone I had the highest expression (FC = 10.36, p < 0.05). The results of our study indicated a high level of MexAB-OprM pump expression in groups of strains isolated in the years 2008-2009 (FC = 12.92, p < 0.03) and 2002-2006 (FC = 5.14, p < 0.03). There were no statistically significant differences in resistance to all tested antibiotics among the various clones. The high level of antimicrobial resistance may have been due to the coexistence of different resistance mechanisms among the studied P. aeruginosa strains. However, this does not exclude the contribution of the MexAB-OprM pump, particularly in resistance to meropenem and ciprofloxacin., (© 2014 APMIS. Published by John Wiley & Sons Ltd.)

Background: The utility of carbapenems, which are considered 'last-line' agents, is being diminished by the growing incidence of various resistance mechanisms in bacteria. We aimed to investigate the molecular mechanism of carbapenem resistance in Enterobacter cloacae recovered from a 76-year-old patient who had undergone coronary artery bypass grafting and repair of the mitral and tricuspid valves. Interestingly, the patient had no prior history of hospital admission abroad., Methods: The Carba-NP test II and synergy testing were performed to confirm carbapenemase activity. PCR was used to detect carbapenemase-encoding genes. Nucleotide and amino acid sequence analysis was performed to identify OXA-48 variants. Moreover, we performed multilocus sequence typing (MLST) of multidrug-resistant (MDR) E. cloacae., Results: We detected no significant increase in zone diameter around disks with inhibitors. However, the Carba-NP test II revealed carbapenemase activity in all isolates. All isolates showed the presence of the exact OXA-48 carbapenemase variant. Furthermore, MLST analysis revealed that the MDR E. cloacae isolates belonged to ST89., Conclusions: We report a case of infection caused by a unique carbapenem-resistant E. cloacae ST89 producing OXA-48 carbapenemase. Interestingly, these pathogens developed resistance to other 'last-resort' agents, namely colistin and tigecycline. There is a crucial need for surveillance programs aimed at screening for carbapenemase-producing Gram-negative bacteria, especially in patients transferred from high-incidence areas., (Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Background: The growing incidence of multidrug resistance (MDR) in bacteria is an emerging challenge in the treatment of infections. Acinetobacter baumannii is an opportunistic pathogen prone to exhibit MDR that contributes significantly to nosocomial infections, particularly in severely ill patients. Thus, we performed research on rifampicin activity against selected MDR OXA-72 carbapenemase-producing A. baumannii strains. Since it is widely accepted that rifampicin should not be used as monotherapy in order to avoid the rapid development of rifampicin resistance, we evaluated the efficacy of combination therapy with imipenem., Methods: Minimal inhibitory concentrations (MICs) of both rifampicin and imipenem were determined by use of the broth microdilution method. Evaluations of the interactions between rifampicin and imipenem were performed by analysis of the fractional inhibitory concentration index (∑FIC), determined using the checkerboard titration method., Results: All tested isolates showed full susceptibility to rifampicin. The checkerboard method revealed synergism in 5 isolates (29%) and an additive effect in another 5 isolates (29%); no difference was reported in the remaining 7 isolates (41%). Strains moderately resistant to imipenem (MIC ≤ 64 mg/l) tended to show synergy or additive interaction., Conclusions: We conclude that in vitro synergism or an additive interaction between rifampicin and imipenem most likely occurs in A. baumannii strains showing moderate resistance to imipenem (MIC ≤ 64 mg/l). Moreover, utilizing this combination in the therapy of infections caused by strains exhibiting higher levels of resistance (MIC > 64 mg/l) is not recommended since in this setting imipenem could not prevent the development of rifampicin resistance.

Acinetobacter baumannii has emerged as a highly problematic hospital-associated pathogen. Different mechanisms contribute to the formation of multidrug resistance in A. baumannii, including the AdeABC efflux system. Distribution of the structural and regulatory genes encoding the AdeABC efflux system among genetically diverse clinical A. baumannii strains was achieved by using PCR and pulsed-field gel electrophoresis techniques. The distribution of adeABRS genes is extremely high among our A. baumannii strains, except the adeC gene. We have observed a large proportion of strains presenting multidrug-resistance phenotype for several years. The efflux pump could be an important mechanism in these strains in resistance to antibiotics., (© 2013.)

Introduction: In recent years an alarming increase of carbapenem-resistant Enterobacteriaceae has been noticed, which creates frequent therapeutic problems, especially for patients residing in intensive care units (ICU). The aim of this study was to evaluate the prevalence of carbapenem-resistant strains of Enterobacteriaceae isolated in the years 2006-2011 at the University Hospital in Bialystok (UHB)., Methods: Based on microbiological analysis reports we conducted a retrospective study of strains resistant to carbapenems. We assigned strains to three carbapenem-resistance phenotypes, and analyzed susceptibility to antibiotics and prevalence of these strains in hospital wards and in clinical specimens collected from hospitalized patients. During a six-year period, 216 strains resistant to carbapenems were tested, which represents 0.96% of all Enterobacteriaceae (n = 22.391) isolated during this period., Results: The greatest number of carbapenem-resistant strains was identified in 2011 (96 strains, 44.44%). Antibiotics that showed the highest activity against strains occurring most frequently (Klebsiella pneumoniae [n = 103] and Enterobacter cloacae [n = 85]) were tigecycline (102 [99.03%] of K. pneumoniae tested strains and 61 [100%] of E. cloacae strains were susceptible), colistin (33 [86.84%] of K. pneumoniae tested strains and 84 [100%] of E. cloacae were susceptible), and amikacin (86 [83.49%] of K. pneumoniae tested strains and 26 [30.58%] of E. cloacae strains were susceptible)., Conclusions: Carbapenem resistance among Enterobacteriaceae isolates showed a trend to increase during the six-year period of study. Because infections caused by carbapenem-resistant strains are frequently life-threatening, the effective strategies to control the spreading of antibiotic resistance are necessary.

The aim of this study was to investigate the prevalence of the aacA4 gene in a population of multidrug resistant strains of P. aeruginosa isolated from bronchial secretions obtained from the Intensive Therapy Unit (ITU). Twelve MDR isolates were tested for antibiotic susceptibility and the presence of the aacA4 gene. In this study, 58.3% of the strains contained (6')-Ib' aminoglycoside acetyltransferase gene. All of the studied strains (aacA4-positive and aacA4-negative) were susceptible only to colistine (100%). Among other antibiotics, the lowest resistance rates were those shown against ceftazidime (14.3% to 20%) and imipenem (28.6% to 40%). Our studies frequently revealed the presence of the aacA4 gene as a factor responsible for resistance; it is probable that other mechanisms of resistance to aminoglycoside antibiotics also occurred.

Acinetobacter baumannii plays an increasing role in the pathogenesis of infections in humans. The bacilli are frequently isolated from patients treated in intensive care units. A growing resistance to antibiotics is leading to the emergence of strains that are multidrug-resistant and resistant to all available agents. The objective of this study was to assess susceptibility to antibiotics and to determine the presence and current level of the extended-spectrum β-lactamases (ESBLs) and attempt to isolate the Acinetobacter baumannii strain carrying the blaPER gene. A total of 51 strains of A. baumannii identified by phenotypic features were examined. That the strains belonged to the species was confirmed by the presence of the blaOXA-51-like; gene. A broth microdilution method was used for antibacterial susceptibility testing. The occurrence of ESBLs was determined using phenotypic double-disk synergy tests. The PCR technique was used to confirm the presence of the blaPER-1; gene encoding ESBL. The most active antibiotics were meropenem, cefepime and ampicillin/sulbactam, with susceptibility shown by 76.5%, 60.8% and 56.9% of the strains, respectively. The strains exhibited the highest resistance (&gt; 75%) to piperacillin, tetracycline, ciprofloxacin and cefotaxime. Phenotypic tests revealed ESBL mechanism of resistance in approximately 20% of Acinetobacter baumannii isolates. However, the PCR technique did not confirm the presence of the blaPER-1; gene in any of the Acinetobacter baumannii strains examined in our hospital. Acinetobacter baumannii strains demonstrate considerable resistance to many groups of antibiotics. Our findings indicate the involvement of enzymes belonging to families other than PER β-lactamase in resistance to β-lactams in A. baumannii.

Introduction: Majority of nosocomial Acinetobacter baumannii strains are highly resistant to many available groups of antibiotics, causing therapy of infections the clinical challenge. The aim of study was to estimate of resistance development to sulbactam, cefoperazone and cefoperazone/sulbactam in Acinetobacter baumannii clinical strains., Methods: Five Acinetobacter baumannii strains (Acb1, Acb2, Acb4, Acb13 and Acb25) were identified by the VITEK 2 GN card and the automatic system VITEK 2 according to the procedure and following the producer's instructions. Additionaly, the belonging of the strains to the species was confirmed by the presence of the bla(OXA-51-like) gene. Initial and after antibiotic exposure MIC values of sulbactam, cefoperazone and cefoperazone/sulbactam were determined by using a broth microdilution method. Antibiotic pressure of examined strains was performed in Mueller-Hinton broth containing 0,5x, 0,9x and 2x initial MIC of individual compounds during six-day passages and next six-day passages without antibiotic presence. The Mann-Whitney U test and Kruskal-Wallis non-prarametric Anova test were used to statistical analysis., Results: Serial passaging of Acinetobacter baumannii strains in the presence of antibiotics caused permanent increasing MIC value independently of used concentrations in the majority of examined strains. The highest MIC value increase of sulbactam was found in Acb4 strain. Even after two passages this isolate changed MIC from 0.5 microg/ml to 4 microg/ml (increase about four levels of concentration). Moreover, after incubation in 0.9x MIC concentration similar observation was noted. No normalization of MIC value of sulbactam after incubation during next six passages without sulbactam was observed. In case of cefoperazone the highest levels of induction were noted in Acb1, Acb13 and Acb25 strains. In these strains, after two passages in presence of cefoperazone (2xMIC) the exceedance of minimal of growth concentration over the highest examined concentration was observed. Similar effects were observed in Acbl strain after stimulation with 0.9x and 0.5x MIC cefoperazone. Return of initial MIC values was received only after induction with 0.5 x MIC cefoperazone. In some cases, no opportunities for evaluation of resistance development was noted, because during stimulation with 2x MIC of used antibiotics concentarations, bactericidal effect was found., Conclusions: Sulbactam, cefoperazone and cefoperazone/sulbactam rapidly induce increasing of resistance in Acinetobacter baumannii clinical isolates. Statistically essential MIC increase after using higher concentration than lower was showed. This effect was particularly visible in the case of stimulation of cefoperazone/sulbactam combination.

Extended spectrum β-lactamases production is one of the most common mechanism of resistance to extended spectrum β-lactam antibiotics is increasing worldwide. Twenty five strains of Klebsiella pneumoniae isolated from clinical specimens were tested. Based on the phenotypic confirmatory test all these strains were defined as ESBL producers named ESBL(+). The plasmid DNA from each strains was used to investigate the presence of blaSHV genes responsible for extended spectrum β-lactamases production. Moreover, susceptibility of these strains to antibiotic other than β-lactams in was tested.

Chronic venous disease (CVD) is an insufficiency of distal veins caused by their partial or total obstruction, endothelial distension and functional disorders. Chronic venous disease of lower limbs is common problem and affects millions of people. In this article we suggest that inflammatory process is involved in the structural remodeling in venous valves and in the venous wall, leading to valvular incompetence and the development of varicose veins.

Antimicrobial resistance due to the continuous selective pressure from widespread use of antimicrobials in humans, animals and agriculture has been a growing problem for last decades. KPC beta-lactamases hydrolyzed beta-lactams of all classes. Especially, carbapenem antibiotics are hydrolyzed more efficiency than other beta-lactam antibiotics. The KPC enzymes are found most often in Enterobacteriaceae. Recently, these enzymes have been found in isolates of Pseudomonas aeruginosa and Acinetobacter spp. The observations of blaKPC genes isolated from different species in other countries indicate that these genes from common but unknown ancestor may have been mobilized in these areas or that blaKPC-carrying bacteria may have been passively by many vectors. The emergence of carbapenem resistance in Gram-negative bacteria is worrisome because the carbapenem resistance often may be associated with resistance to many beta-lactam and non-beta-lactam antibiotics. Treatment of infections caused by KPC-producing bacteria is extremely difficult because of their multidrug resistance, which results in high mortality rates. Therapeutic options to treat infections caused by multiresistant Gram-negative bacteria producing KPC-carbapenemases could be used polymyxin B or tigecycline.

More and more is known about the role of venous wall abnormalities and valvular incompetence in the development of chronic venous disorders (CVD). Unfortunately detailed mechanisms of CVD pathophysiology are not well understood. Recent studies focus on involvement of the inflammatory process in the structural remodeling of venous valves and venous wall. The aim of this study is to investigate and to document the memory T cells homeostasis in CVD patients. In this study we present lymphocytic changes in blood from varicose veins in terms of total CD4+ and CD8+ T cells and their particular subsets of memory T cells: TN, TCM and TEM. Results suggest that immunological memory may be involved in the CVD development.

T cell memory in comparison with B cell memory is not well understood. This review focuses on CD8+ and CD4+ memory T cells. In this article we try to define memory cells and also present models of memory T cells formation. We would also like to delineate their differentiation into distinct subsets. Long-lived memory T cells consist in two main subsets: TCM and TEM. Recent studies have shown that not all cells considered to be memory cells differentiate into TCM and TEM, but a small proportion of theses cells exhibit naive cells phenotype. Memory T cells constitute a heterogeneous population of cells. In this study we lay stress on characteristic of main memory T cells subsets and their alleged participation in immune response upon reexposure to the Ag.