Moderate Genetic Diversity with Extensive Antimicrobial Resistance Among Multidrug-Resistant Acinetobacter baumannii in a Referral Hospital in Northeast Iran

Background: Acinetobacter baumannii is one of the major opportunistic pathogens with increasing clinical significance, particularly in the Hospital setting. Objectives: The study aimed to analyze the antibiotic resistance determinants in multidrug-resistant A. baumannii (MDRAB) isolates collected after an outbreak, with regard to the infection prevention control (IPC) interventions to eradicate the outbreak. Methods: Thirty nine isolates of MDRAB were collected during six months of the study after the outbreak. Infection prevention control was successful only for the first three months after the intervention. Antimicrobial susceptibility testing and minimum inhibitory concentrations (MICs) were determined by E-test. In addition, various resistance genes and the clonal relatedness of the isolates were performed by PCR and REP-PCR. Results: All isolates were MDRAB while being susceptible to colistin. The prevalence of bla(ADC), bla(TEM), blaOX(A24), bla(VIM), and bla(IMP) was 82%, 100%, 70%, 61%, and 5%, respectively. bla(OXA51), bla(OXA23), and ISAba1 were detected in all isolates, but bla(OXA58) was not. Moreover, ISAba1 was located upstream to bla(OXA23) and blaADC in 100% and 38.4% of the isolates, respectively. The most prevalent AME was aadB (100%). Even though adeB and tetB efflux pumps were found in 100% and 95% of the isolates, respectively, tetA was not characterized. REP-PCR revealed five clusters of which, approximately 51% of the strains belonged to cluster C. Conclusions: Regarding the molecular approach, the effectiveness of IPC and epidemiological context has been identified. Stringent infection-control measures are urgent to restrict the outbreak.