Application of Multiplex PCR for the Identification of Oxacillinase Genes and Determination of Antibiotic Resistance Pattern in Environmental Isolates of Acinetobacter baumannii in ICU

Background: Acinetobacter baumannii is a common cause of nosocomial infections. A prominent feature ofthese bacteria is resistance to carbapenems. This study aimed to identify OXA genes encoding oxacillinase inAcinetobacter baumannii isolates.Methods: This cross-sectional descriptive study was performed on ۲۵ environmental A. baumannii isolatescollected from ICU over ۸ months. Definitive identification of isolates was performed by biochemical tests andpolymerase chain reaction (PCR) of ۱۶s rRNA gene. Antibiotic susceptibility testing was performed on Müller-Hinton agar medium by disk diffusion and E-test. Antibiogram and multiplex PCR data of beta-lactamase geneswere collected and analyzed at a significance level of P < ۰.۰۵ using SPSS ۲۲.۰.Results: Except for one isolate, all isolates (۹۶%) were sensitive to polymyxin B and ۸۰% of isolates weresensitive to oxacillin. All isolates were sensitive to meropenem, ampicillin/sulbactam, gentamicin, amikacin,piperacillin, and carbenicillin. The results showed that ۲۵ isolates (۱۰۰%) had OXA-۵۱ gene, ۲۱ isolates (۸۴%)had OXA-۵۸ gene, one isolate (۴%) had OXA-۲۴ gene, and none of the isolates contained OXA-۲۳ gene. Onlyisolate No.۱۰ had three oxacillinase genes simultaneously and it was resistant to oxacillin, polymyxin B, andcephalothin.Conclusions: The study showed that environmental isolates of ICU do not have pathogenic genes present in theclinical isolates, and how these genes are transferred to the peripheral isolates is an important point that shouldbe studied. Identification of genes encoding carbapenem resistance may help to understand the mechanisms ofresistance transfer in A. baumannii. The lack of the OXA-۲۳ gene plays an important role in the susceptibility ofisolates to antibiotics and non-emergence of resistant strains.

Keywords:

Acinetobacter baumannii , Carbapenems , Antibiotic resistance , Nosocomial infection