ABSTRACT
Coagulase Negative Staphylococci species (CoNS) have been recognized as etiological agents in wide variety of infections, patients with implants and devices. CoNS has the ability to produce biofilm which is responsible for resistance to host defense mechanisms and to the antibiotics. Hence this study was undertaken to study biofilm production by the isolated species of CoNS by three different phenotypic methods and compare these methods for biofilm production.METHODSIn this cross-sectional study, 200 CoNS isolates from clinically significant samples were identified up to species level by conventional phenotypic methods. Biofilm production was detected by Tissue Culture Plate method (TCP), Standard Tube method (ST) and Congo Red Agar Plate method (CRA). Biofilm production in test strains were compared with reference strains.RESULTSOut of 200 CoNS isolates, 122 were positive by TCP method, 106 by ST method & 67 by CRA method for biofilm production. Considering TCP method as gold standard, sensitivity, specificity, PPV and NPV of ST & CRA method were found to be 86.06%, 98.71%, 99.05%, 81.91% and 54.09%, 98.71%, 98.50% and 57.89% respectively. Analysis of Kappa agreement between TCP and ST method showed good agreement while between TCP & CRA, moderate agreement. Comparison of ST and CRA method with TCP by Pearson correlation coefficient test showed strong association between ST and TCP method (p= 0.006) & poor association between TCP and CRA method. (p<0.01).CONCLUSIONSBiofilm production by TCP method was higher compared to the other methods. ST method is comparable to TCP but CRA alone cannot be considered for biofilm detection in CoNS. ST method can be used in routine as it gives reliable results with good sensitivity & specificity and is easy to perform.