Comparison of two methods for quantification of Acinetobacter baumannii biofilm formation

Introduction: ‏ Medical devices are made from a variety of materials such as polypropylene, polycarbonate, poly styrene, glass and etc. by attaching to this surfaces, Acinetobacter baumannii can form biofilms and then cause several device associated infections. Biofilms are communities of bacteria attached to the surfaces. In this study, biofilm formation ability in clinical isolates of Acinetobacter baumannii was assessed by two methods on different surfaces. Materials and methods: ‏ Biofilm formation by 75 clinical isolates of A. baumannii was evaluated on polycarbonate surface (microtiter plate) and polypropylene surface (falcon) by crystal violet and 2,3-Bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide salt (XTT tetrazolium sodium salt) assay methods. Falcon or tube method was carried out under static and agitation conditions. Results: ‏ Results showed the most isolates can form biofilm but higher numbers of isolates form biofilm on polypropylene surface under agitation. XTT method confirmed strong biofilm formation ability of 10 isolates. Discussion and conclusion: Each of the two assays showed an excellent applicability for the quantification of biofilms. The Crystal violet assay is cheap, easy and is usually used for the quantification of biofilms formed by microorganisms but XTT is more reliable and repeatable. Most of A. baumannii isolates have potential to form biofilm on the medical devices which may result in device-associated infections