Frequency of bap and cpaA virulence genes in drug resistant clinical isolates of Acinetobacter baumannii and their role in biofilm formation

Abstract

<strong><em>Objective(s)</em></strong>: <em>Acinetobacter baumannii</em> has a high propensity to form biofilm and frequently causes medical device-related infections with multiple-drug-resistance in hospitals. The aim of this work is to study antimicrobial resistance and the role of<em> bap</em> and <em>cpaA</em> genes in biofilm formation by <em>A.</em> <em>baumannii</em> to understand how this pathogen persists in the hospital environment.<br /> <strong><em>Materials and Methods: </em></strong>Theantibiotic resistance profile and <em>in</em> <em>vitro</em> biofilm-forming ability of one hundred clinical isolates of <em>A. baumannii</em> was evaluated by disc diffusion and crystal-violet staining methods, respectively. Isolates were tested for the presence of <em>bap</em> and <em>cpaA</em> genes.<br /> <strong><em>Results:</em></strong> The isolates were highly resistant to cefepime, third-generation cephalosporins, ciprofloxacin, cotrimoxazole, aminoglycosides and carbapenems. Moreover, four isolates were resistant to colistin. Quantification of biofilm showed that 43% of the isolates were strong biofilm-producer. Furthermore, 32% of the isolates exhibited moderate biofilm-formation and showed initial binding activity. Frequency of <em>bap</em> and <em>cpaA</em> were determined 92% and 36%, respectively.<br /> <strong><em>Conclusion:</em></strong> There was strong association between the presence of <em>bap</em> gene and biofilm formation by <em>A. baumannii</em> isolates (<em>P</em>=0.003). In addition, multidrug resistant isolates produced stronger biofilm than other isolates (<em>P</em>=0.0001). These results indicate importance of biofilm in resistance of isolates and effect of presence of <em>bap</em> gene in biofilm formation by <em>A. baumannii </em>strains.