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Introduction: Escherichia coli (E. coli) is one of the major pathogens causing urinary tract infection (UTI). The Spread of Extended-Spectrum β-Lactamases (ESBL)/AmpC enzymes has become a major issue, particularly due to the antibiotic therapeutic failures that result in less favorable patient outcomes, including higher mortality. This study aimed to investigate the prevalence of phenotypic and genotypic beta-lactamase resistance in E. coli strains isolated from the urine sample. Methods: A total of 231 E. coli isolates were collected from urine samples of patients from Tehran Children's medical center hospital between 2012 to 2015. The antibiotic resistance pattern of clinical isolates was determined by using the disk diffusion method. AmpC β-lactamases and ESBLs, alone and in combination, could reliably be detected using a disc diffusion method. Genes encoding beta-lactamases were detected by PCR method using β-lactamase gene-specific primers. Results: All isolates of the present study were resistant to ampicillin and cefazoline. The resistance rate to other antibiotics was as follows: trimethoprim-sulfamethoxazole 85.7%, gentamicin 37.6%, levofloxacin 35.9%, and cefoxitin 24.6%. A high sensitivity rate was observed against meropenem and nitrofurantoin. Among collected isolates, 81.5% were ESBLsproducers. The prevalence of ESBLs production in CTX-M, SHV, and TEM was 100%, 35%, and 46.7%, respectively. Among 68 presumptive AmpC producers, CIT was the most prevalent detected gene, while FOX was the least seen. Conclusion: Regarding the production of ESBL by some E. coli isolates, phenotypic detection for determining the antibiotic profile and resistance genes is recommended to formulate an effective antibiotic therapy. [ABSTRACT FROM AUTHOR]

Antibiotic resistance in Klebsiella pneumoniae isolates, particularly resistance to colistin, has become a growing concern. This study seeks to investigate the upregulation of specific genes (pmrA , pmrB , pmrC , phoQ , phoP , and arnT) that contribute to colistin resistance in K. pneumoniae isolates collected from human clinical samples in Tehran, Iran. Thirty eight K. pneumoniae isolates were obtained and subjected to antibiotic susceptibility testing, as well as evaluation for phenotypic AmpC and ESBL production according to CLSI guidelines. The investigation of antibiotic resistance genes was conducted using polymerase chain reaction (PCR), whereas the quantification of colistin resistance related genes expressions was performed via Real-Time PCR. The highest and lowest antibiotics resistance were observed for cefotaxime 33 (86.8%) and minocycline 8 (21.1%), respectively. Twenty-four (63.2%) and 31 (81.6%) isolates carried AmpC and ESBLs, respectively. Also, antibiotic resistance genes containing bla NDM , bla IMP , bla VIM , bla SHV , bla TEM , bla CTXM , qnrA, qnrB, qnrS , and aac(6')-Ib were detected in K. pneumoniae isolates. Only 5 (13.1%) isolates were resistant to colistin and the MIC range of these isolates was between 4 and 64 μg ml−1. Upregulation of the pmrA , pmrB , pmrC , phoQ , phoP , and arnT genes was observed in colistin-resistant isolates. The colistin-resistant isolates were found to possess a simultaneous presence of ESBLs, AmpC, fluoroquinolone, aminoglycoside, and carbapenem resistant genes. This study reveals escalating antibiotic resistance in K. pneumoniae , with notable coexistence of various resistance traits, emphasizing the need for vigilant surveillance and innovative interventions. [ABSTRACT FROM AUTHOR]

Objectives: Drug resistance among gram-negative bacteria is a worldwide challenge. Due to the importance of drug-resistant Klebsiella pneumoniae and Escherichia coli strains in hospital-acquired infections, we aimed to determine the phenotypic and genotypic characteristics of ESBL-, AmpC-, and carbapenemase-producing isolates obtained from hospitalized patients in Tehran and Ilam (Iran).Materials and Methods: In total, 90 K. pneumoniae isolates and 65 E. coli isolates were collected from various infections. Phenotypic identification of bacterial isolates was performed using standard methods. Phenotypic screening of ESBL, AmpC, and carbapenemase enzymes was carried out. Detection of ESBL, AmpC, and carbapenemase genes was also performed by the PCR method.Results: Phenotypic detection tests showed that 36 (40%) K. pneumoniae and 23 (35.4%) E. coli isolates were ESBL producers. Moreover, 18 (20%) and 6 (9.2%) K. pneumoniae and E. coli isolates were AmpC producers, respectively. Modified Hodge test results indicated that 39 (43.3%) K. pneumoniae and 18 (27.7%) E. coli isolates produced carbapenemase. Molecular tests showed that 40% of K. pneumoniae and 36.9% of E. coli isolates were ESBL positive. AmpC was detected in 24.4 and 13.8% of K. pneumoniae and E. coli isolates. Carbapenemase was detected in 34 (37.8%) K. pneumoniae and 13 (20%) E. coli isolates. -Conclusion: In this study, 3 K. pneumoniae isolates simultaneously carried ESBL, AmpC, and carbapenemase genes. Up-to-date strategies such as combination therapy or utilization of new antimicrobial agents might help to combat such drug-resistant organisms. [ABSTRACT FROM AUTHOR]

Klebsiella spp. are among the most frequently isolated bacteria from burn wounds. These organisms are among the most important opportunistic pathogens, causing hospital-acquired and healthcare-associated infections worldwide. Limited information is available about prevalence of AmpC-producing Klebsiella pneumoniae from burn patients. Therefore, the aim of this study was to determine the characterization of AmpC beta-lactamase among K. pneumoniae isolated from burn patients. Samples were collected from wound specimens of patients with burn injury from a burn hospital in Tehran during 18 months (March 2015 to August 2016). For phenotypic detection of AmpC beta-lactamase, disk diffusion method with cefoxitin was used for screening, AmpC disk test and boronic acid inhibitor-based method were used as confirmatory tests. Polymerase chain reaction (PCR) was performed to screen all isolates with AmpC genes including ACCM, DHAM, EBCM, FOXM, MOXM, and CITM. Finally, PCR products were validated using sequencing. During this study, 102 isolates of K. pneumoniae were collected. Among these isolates, 52.9% suspected as AmpC producer by disk agar diffusion cefoxitin screening method. By confirmatory phenotypic methods, 19.6% of isolates considered as AmpC producer. Molecular analysis revealed 43.1% of cefoxitin-resistant isolates harbored at least one of the AmpC genes including CITM (22.5%), EBCM (21.5%), DHAM (7.8%), and FOXM (0.98%). In addition, 5.8% of isolates harbored two AmpC genes and 2.9% harbored three AmpC genes. In conclusion, K. pneumoniae is becoming a serious problem in burn patients. Accurate and precise methods and guidelines should be designed for detection of antibiotic-resistant mechanisms. Our data showed the high rate of AmpC beta-lactamase among K. pneumoniae isolated from burn patients, which limit the treatment options. Therefore, the results of this study can provide evidence to help for appropriate treatment of burn patients. [ABSTRACT FROM AUTHOR]

Background/aim: To study the prevalence of blaVIM and blaIMP genes in metallo-β-lactamase (MBL)-producing burn isolates of Pseudomonas aeruginosa in relation with AmpC and extended-spectrum β-lactamase (ESBL) production. Materials and methods: Thirty-two carbapenem-resistant MBL-producing P. aeruginosa burn isolates from Shahid Motahari Burn Hospital in Tehran were employed. Antibiotic susceptibility was determined to 13 antibiotics including imipenem and meropenem by disk diffusion. AmpC and ESBL production was detected by the AmpC disk test and combined disk diffusion assay, respectively. blaIMP and blaVIM gene carriage was shown by polymerase chain reaction and type-specific primers. Results: AmpC production was observed in 81% and ESBL production was detected in 12.5% of the isolates. blaIMP carriage was observed in 56.25% and blaVIM gene in 46.8% of the isolates. Surprisingly, 43.5% of the isolates carried both blaIMP and blaVIM genes. Conclusion: We think that this is the first report on the cocarriage of blaIMP and blaVIM in P. aeruginosa. There was also a strong association between MBL gene carriage and AmpC β-lactamase production. [ABSTRACT FROM AUTHOR]