Evaluation of Ica Gene in Comparison with Phenotypic Methods for Detection of Biofilm Production by Coagulase Negative Staphylococci in a Tertiary Care Hospital

Abstract

Background: Biofilm producing bacteria are responsible for several chronic infections and are difficult to treat as they show much greater resistance to antibiotics. The major virulence factor determining the pathogenicity of CoNS has now well defined and found to be biofilm production. Objective: The study was conducted to isolate and characterize Coagulase Negative Staphylococci (CoNS) and their ability to form biofilms was evaluated by phenotypic and genotypic methods. Materials and Methods: A total of 96 clinical isolates of CoNS were characterized and subjected to biofilm detection by tissue culture plate method (TCP), tube method (TM), congo red agar method (CRA) and PCR. Results: Staphylococcus epidermidis was the most commonly isolated species 76(79.17%). The ica gene was present in 35 (36.45%) of CoNS isolates which were detected as biofilm producers by TCP. Biofilm producing isolates showed higher antibiotic resistance(72.1%). Majority of biofilm producers had strong association with medical device related infections. Conclusion: To compare PCR based dectection method for presence of ica genes with TCP, the test share the specific identification rates. The sensitivity and specificity of TCP method in detection of biofilm was high in comparison with TM and CRA. TCP can be recommended as a general screening test for biofilm detection.

Keywords

• antibiotic resistance
• congo red agar method
• tissue culture plate method
• tube method