Molecular epidemiological analysis of integron gene cassettes and tetA/tetB/tetD gene associations in Escherichia coli strains producing extended-spectrum beta-lactamase (ESBL) in urine cultures

Background. Epidemiological studies of tetracycline (TE) resistance genes and integron gene cassettes, particularly in urine samples, are limited in Turkey. Objectives. To investigate antibiotic susceptibility profiles, extended-spectrum beta-lactamase (ESBL) positivity, tet gene types, class-I/-II integron gene cassettes, and clonal relationships among tet-resistant isolates of Escherichia coli from urine cultures of outpatients. Materials and methods. Isolates were identified using conventional methods and the automated Vitek (R) 2 Compact system. Antimicrobial susceptibility was performed for 19 antibiotics. The ESBL production was performed using the Kirby-Bauer disk diffusion test. The double disk synergy test was used for confirmatory testing. Polymerase chain reaction (PCR) was used to determine the presence of class-I/-II integron gene cassettes and tetA, tetB and tetD resistance genes. The pulsed-field gel electrophoresis typing was performed to identify clonal relations. Results. A total of 121 isolates were obtained and found to be resistant or sensitive to ampicillin and amikacin/imipenem. Resistance to ceftazidime, cefotaxime and ceftriaxone was determined to be 31.3%, 77.6% and 83.1%, respectively. Tetracycline resistance was detected in 82 isolates, mostly caused by the tetB gene. No tet gene was detected in the remaining 39 isolates. Although 64 out of 82 isolates carried a class-I integron, only 4 had a class-II integron (with sizes of 800-2900 base pairs). Furthermore, tet genes were identified with different size class-I integron gene cassettes. However, tet genes were not detected in any isolate identified with integron gene cassette II. Clonally, the isolates were found to be related in subgroups because they were community-acquired. Conclusions. This study showed thatthe tetB gene is most commonly found in E. coli isolates grown in urine samples from the Turkish population

Antimicrobial susceptibility and molecular characterization of multidrug-resistant acinetobacter baumannii Isolated in an university hospital

WOS: 000387771500002PubMed: 28124957Acinetobacter baumannii, an aerobic, non-motile, gram-negative bacterium is an important nosocomial pathogen which shows resistance to the most antibiotics. Carbapenems are the most commonly used antibiotics for the treatment of infections caused by this pathogen. However the emergence of resistance against carbapenems in an increasing rate generates serious problems for antimicrobial therapy. The aims of this study were to detect the antibiotic susceptibility, and the presence of bla(OXA) resistance genes of clinical A. baumannii isolates and to determine the clonal relationship between these isolates. A total of 79 A. baumannii strains isolated from various clinical specimens (37 respiratory tract samples, 11 wound, 10 blood, 8 catheters, 6 tissue, 5 urine, 2 abscess) of the patients admitted to Mersin University Medical School Hospital between May 2012-January 2013, were included in the study. The isolates were identified by conventional methods and Vitek (R) 2 Compact automated system. Antibiotic susceptibilities of the isolates were determined by Kirby-Bauer disk diffusion method and evaluated according to CLSI criteria. The presence of bla(OXA-51), bla(OXA-23), bla(OXA-24), bla(OXA-48) and bla(OXA-58) genes were detected by an in-house polymerase chain reaction (PCR), and the clonal relationship between the isolates were identified by pulsed-field gel electroforesis (PFGE) using the ApaI restriction enzyme. In our study, all of the isolates were susceptible to colistin, while the resistance rates against piperacillin-tazobactam, ciprofloxacin, imipenem, meropenem, cefoperazone/sulbactam, trimethoprim-sulfamethoxazole, ceftazidime, levofloxacin, gentamicin, tetracycline, ampicillin-sulbactam, amikacin, netilmicin and tigecycline were 97.5%, 96.2%, 94.9%, 94.9%, 93.6%, 91.1%, 88.6%, 86%, 83.6%, 77.2%, 69.6%, 55.7%, 27.8% and 3.8%, respectively. All the isolates were identified as A. baumannii with the OXA-specific PCR and OXA16S rDNA sequence analysis. All of the isolates (100%) harboured bla(OXA-51) and 71 (89.9%) harboured bla(OXA-23) gene, however they were all negative for bla(OXA-24), bla(OXA-48) and bla(OXA-58) genes. According to PFGE results 10 pulsotypes were identified, of these eight pulsotypes formed 77 (97.5%) similar strains with indistinguishable PFGE profiles ranging between 3-30 [A (n=30), B (n=20), C (n=9), D (n=5), E (n= 4), F (n=3), G (n=3), H (n=3)]. When compared with the other clones, clones A and B were dominant among the samples and they have exhibited high level of antibiotic resistance. The rest two pulsotypes [I (n=1), J (n=1)] were in close relation with the main cluster. No common outbreak isolate was detected, but the relationship between the majority of the strains pointed out that there was a cross contamination problem in our hospital. In conclusion bla(OXA-51) and bla(OXA-23) were detected as predominant genes responsible from carbapenem resistance in our clinical A. baumannii strains, and it was considered that the high prevalence of clones A and B may constitute a threat in terms of hospitalized patients