Prevalence of IMP and SPM Genes in Clinical Isolatesof Carbapenem Resistant Acinetobacter baumannii in Educational Hospitals of Sari, Iran

Background and purpose: Acinetobacter Baumannii is an opportunistic bacterium, which is considered as a concern in hospitals throughout the world due to high antibiotic resistance rate. The aim of this study was to investigate the prevalence of carbapenem resistance genes in clinical isolates of this bacterium. Materials and methods: In this study, 100 clinical isolates of Acinetobacter Baumannii were collected from hospitals affiliated to Mazandaran University of Medical Sciences. Antibiotic susceptibility patterns of the bacteria were evaluated using disk agar diffusion method and agar dilution method was used to determine the minimum inhibitory concentration of colistin. Carbapenemase-producing isolates were detected by phenotypic Combined Disk Test (CDT) and PCR method was performed to investigate the presence of IMP and SPM genes in the isolates. Results: The highest and the lowest antibiotic resistance rates were to piperacillin (99%) and colistin (7%), respectively. Among the isolates studied, 97 were found to be resistant to carbapenems, while phenotypic evaluation (CDT) showed metallo-beta-lactamase production in 95 isolates. Of the strains resistant to carbapenems, only two (2.06%) contained the IMP gene, while none of these isolates carried the SPM metallo-beta-lactamase. Conclusion: According to the findings, other mechanisms of resistance such as increasing the activity of the efflux pumps, decreasing the expression of outer membrane proteins, excessive expression of the AmpC enzyme or production of other carbapenemases can be effective in resistance to carbapenem in Acinetobacter Baumannii species isolated in this area.