Evaluation of phenotypic and genotypic detection methods for biofilm-forming methicillin-sensitive and methicillin-resistant Staphylococcus aureus clinical isolates

Three hundred Staphylococci (MRSA150, MSSA150) isolates from different clinical samples were tested for the production of slime. Phenotypic characterization was performed using the tube method, Congo red agar (CRA), modified Congo red agar (MCRA), and microtiter plate assay (MPA), while the presence of icaADBC genes required for biofilm were assessed using PCR. In all the isolates tested, there was a 44.66 and 100% correlation between the lack of production of slime (red colonies) on CRA and the presence of the icaADBC genes, and between slime production (black colonies) on MCRA and the tube method established in this study with the presence of icaADBC genes, respectively. The standard test method (MPA) used to quantify production of biofilm revealed that all isolates in the present study were positive using a spectrophotometric assay. In conclusion, this study led to the development and the establishment of a method for identifying and detecting Staphylococcus aureus biofilm production, whereby the phenotypic characterization developed was molecular-based. In addition, the modified Congo Red agar was optimized to confirm slime production in contrast to previous published selective media.