The diversity of class B and class D carbapenemases in clinical Acinetobacter baumannii isolates

Wide distrubution of multidrug-resistant Acinetobacter baumannii strains has become a foremost concern in hospital environments. Treatment of infections caused by multidrug resistant strains has conventionally involved the use of β-lactams such as carbapenems. In this study, we report the distribution of carbapenemase genes in A. baumannii isolated from hospitalized patients. The study was conducted on 110 non-repetitive A. baumannii isolates collected from hospitalized patients, over a nine-month period. Clinical isolates were examined by conventional susceptibility testing, using the disk-diffusion method and multiplex polymerase chain reaction to detect acquired carbapenemase genes. All of the isolates were completely resistant to TOB, SXT, IPM, MEM, CTX, CRO, FEP, CAZ, CIP, PTZ, PIP and were susceptible to colistin, but moderately susceptible TET (2.72%), AK (4.54%) and GEN (3.63%). The prevalence of bla-OXA-51like, bla-OXA-23like, bla-OXA-24like, bla-OXA-58like, blaSIM and blaSPM genes was 100%, 96.36%, 35.45%, 7.27%, 7.27% and 3.63%, respectively. bla-GIM and bla-VIM genes were not detected among the strains. Our results suggest that OXA-type carbapenemase genes plus class B β-lactamases contribute to carbapenem resistance in the collected isolates. Therefore, quick identification of these resistant genes using molecular approaches is critical in limiting the spread of infections caused by A. baumannii. Drug administration correction of the physicians, based on antibiotic susceptibility testing and more knowledge on the nosocomial infection control policies as essential need.