Assessment of various detection methods of biofilm formation in Staphylococcus aureus clinical isolates

As an important factor in pathogenicity, the ability of Staphylococcus aureus to produce biofilm increases its stability in the environment and living host. Biofilms formed by S.aureus, especially those related to the implant of medical devices, can act as a physical barrier against antibiotics and the host's immune system, leading to chronic or persistent infections. Hence, implementation of efficient diagnostic tests for the detection of biofilm formation can help reduce the disease burden. The purpose of this study was to assess different methods for the detection of biofilm formation in 40 S.aureus isolates.

A total of 40 non-duplicate S. aureus clinical isolates were identified. Biofilm formation was detected by Tissue Culture Plate (TCP), tube method (TM) and Congo red agar (CRA) methods and PCR assay was used to detect icaA and icaD genes. 

Among all S. aureus isolates, 21(52.5%) contained both icaA and icaD genes and icaD gene was present in all biofilm positive isolates. Tissue culture plate, Congo red agar, and tube method detected 30%, 42.5%, and 67.5% biofilm formation isolates, respectively.

According to the results, tissue culture plate with supplemented glucose showed the best correlation with the results of molecular assay and can be used as a reliable method to detect biofilm formation in clinical isolates of S. aureus.