Iranian Journal of Medical Microbiology

Objective: The aim of this study was to investigate the relationship between biofilm formation and antibiotic resistance in clinical Acinetobacter baumannii isolates.
Methods: A total of 40 clinical A. baumannii isolates from Iranian hospitalized patients were collected. Disk diffusion method was performed to assess the antimicrobial resistance. A crystal violet microtiter plate was used to assay the biofilm-forming ability, and the polymerase chain reaction (PCR) method was employed to determine the frequency of biofilm-related genes (bfmR, bfmS, pgaA, bap, ompA, csuE, and abaI). The relationship between biofilm forming ability and resistance to antibiotics was statistically analyzed using Fisher's exact test and p≤ 0.05 was considered significant.
Results: All A. baumannii isolates were multidrug-resistant (MDR). The frequency of the extensively drug-resistant (XDR) was 80%, and the remainder were pan-drug-resistant (PDR). Most of the MDR isolates (85%) were strong biofilm formers, and the rest of them were moderate biofilm formers. All of the PDRs and 81.25% of XDRs formed strong biofilms. The bfmR, bfmS, pgaA, bap, and ompA genes were existed in all of the MDRs. The csuE and abaI genes were detected in 97.5% and 82.5% of the MDRs respectively. All of the XDRs carried the csuE gene, and 90.62% possessed the abaI gene. Among the PDR isolates, 87.5% presented the csuE gene, and 50% exhibited the abaI gene.
Conclusion: The presence of biofilm-forming genes (bfmR, bfmS, pgaA, bap, ompA, csuE, and abaI) may be related to antibiotic resistance in clinical A. baumannii isolates, although a clone of PDRs is evolving with strong biofilm forming ability and lacking abaI gene.