Oxacillinase Gene Distribution, Antibiotic Resistance, and Their Correlation with Biofilm Formation in Acinetobacter baumannii Bloodstream Isolates

Objectives: The limitations of treatment options in bloodstream infections caused by multidrug-resistant Acinetobacter baumannii (MDRAB) have been related to high morbidity and mortality. The aim of our present study was to determine antimicrobial susceptibility profiles, molecular resistance patterns, and biofilm properties of A. baumannii isolated from bloodstream infections. Materials and Methods: In the present study, a total of 44 A. baumannii bloodstream isolates were included. Antimicrobial susceptibility profiles and biofilm formation ability were assessed. The distribution of class D carbapenemases, ISAba1, ISAba1/blaOXA-23, blaNDM-1, mcr-1, and ompA was investigated by polymerase chain reaction (PCR). Arbitrarily primed-PCR (AP-PCR) was performed to evaluate clonal relationships. Results: A total of 32 isolates were MDRAB, whereas 6 isolates were also resistant to colistin without mcr-1 positivity. All isolates were harboring blaOXA-51 gene, whereas blaOXA-23 positivity was 63.6%. Fifty percent of the isolates had ISAba1. ISAba1 upstream of blaOXA-23 was determined in 18 isolates. None of the isolates were positive for blaNDM-1 gene. Majority of the strains were strong biofilm producers (86.8%). A total of 56.8% of the isolates were positive for ompA gene with no direct association with strong biofilm formation. However, blaOXA-51 + 23 genotype and trimethoprim-sulfamethoxazole resistance showed a significant relationship with biofilm formation. AP-PCR analysis revealed six distinct clusters of A. baumannii. Conclusions: Herein, majority of the A. baumannii blood isolates were characterized as blaOXA-51+OXA-23 carbapenemase genotype and were strong biofilm formers. None of the isolates were positive for blaNDM-1, which was promising. Resistant isolates were tended to form strong biofilms. Our results highlight the emergence of oxacillinase-producing MDRAB isolated from bloodstream with high biofilm formation ability.