title: [Antimicrobial susceptibility and molecular characterization of multidrug-resistant Acinetobacter baumannii isolated in an university hospital].
abstract: Acinetobacter 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 blaOXAresistance 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®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 blaOXA-51, blaOXA-23, blaOXA-24, blaOXA-48 and blaOXA-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 blaOXA-51and 71 (89.9%) harboured blaOXA-23gene, however they were all negative for blaOXA-24, blaOXA-48and blaOXA-58genes. 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 blaOXA-51and blaOXA-23were 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.
authors.affiliation: Giresun University Faculty of Medicine, Department of Medical Microbiology, Giresun, Turkey. sdirekel@yahoo.com.
authors.forename: Şahin
authors.initials: Ş
authors.lastname: Direkel
authors.forename: Ayşegül
authors.initials: A
authors.lastname: Çopur Çiçek
authors.forename: Alper
authors.initials: A
authors.lastname: Karagöz
authors.forename: Nebahat
authors.initials: N
authors.lastname: Aydoğan Ejder
authors.forename: Efdal
authors.initials: E
authors.lastname: Oktay
authors.forename: Nuran
authors.initials: N
authors.lastname: Delialioğlu
authors.forename: Osman Birol
authors.initials: OB
authors.lastname: Özgümüş
authors.forename: Rıza
authors.initials: R
authors.lastname: Durmaz
mesh_terms: D000151:Acinetobacter Infections / Q000382:microbiology*; D040981:Acinetobacter baumannii / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D015780:Carbapenems / Q000494:pharmacology; D003428:Cross Infection / Q000382:microbiology*; D015252:Deoxyribonucleases, Type II Site-Specific; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D016521:Electrophoresis, Gel, Pulsed-Field; D019450:Genes, MDR; D006785:Hospitals, University; D006801:Humans; D016133:Polymerase Chain Reaction
chemical_list: D015780:Carbapenems; D015252:Deoxyribonucleases, Type II Site-Specific; C038485:GGGCCC-specific type II deoxyribonucleases