Biofilm forming capacity in staphylococci and comparison between its Species

Introduction: Staphylococci are increasingly being recognized for their biofilm forming capacity leading to chronic infections and treatment failures. Owing to their burden on healthcare services, the choice of the method of biofilm detection in a routine diagnostic laboratory needs to be established. Methods: Institutional Ethics Committee approval was obtained before study initiation. Clinical isolates of Staphylococcus aureus(n = 100) and of Coagulase negative Staphylococci (CoNS, n = 100) were tested for their biofilm forming capacity. The methods employed were congo red agar method (CRA), tube method (TM) and tissue culture plate method (TCPM) with TCPM as the gold standard reference. Observations and Results: Twelve out of 100 S aureus & sixteen out of 100 CoNS were found to be biofilm producers. Amongst the CoNS species, highest production of biofilm was observed in strains of S. epidermidis(10/24). Isolates (viz CoNS) obtained from medical devices showed higher rates of biofilm formation. Higher percentage of biofilm producers were methicillin resistant(20/28). Out of the 28 isolates detected as biofilm producers by TCPM, 24 were detected by Tube method & only 18 by CRA method. Thus, CRA method had low sensitivity (64.28%) as compared to tube method (85.17%). Conclusion: Medical devices should be used only when indicated and removed on the first indication to do so. Due to its higher accuracy and ease of testing, tube method can be easily incorporated in a routine diagnostic laboratory for detecting biofilm forming capacity in Staphylococci isolated from clinical specimens.