Detection of biofilm formation and analysis of biofilm-associated genes of methicillin-resistant Staphylococcus aureus in clinical isolates / 实用医学杂志

ABSTRACT

Objective To detect biofilm formation and biofilm-associated genes of methicillin-resistant Staphylococcus aureus (MRSA) in clinical isolates. Methods The biofilm were determined by microtiter plate assay (MPA) and congo red agar (CRA) and the biofilm-associated genes icaA,sarA,fnbA,fnbB were detected by PCR in 33 strains of MRSA in clinical isolates. Results Of the 33 MRSA isolates, 29(87.9%) were MPA positive, 16(48.5%) were CRA positive; The icaA gene was present in 39.4% of isolated strains. Furthermore, 69.7% of strains harboured the sarA gene, 39.4% were fnbA positive and 75.8% were fnbB positive. As many as 87.9% strains had the ability to form biofilm in vitro. 44.8% of MRSA formed biofilm in ica-dependent mechanism and 55.2% of MRSA isolates formed biofilm in ica-independent mechanism. Of the biofilm positive MRSA, 75.9% were sarA positive, 37.9% were fnbA positive and 79.3% were fnbB positive. Conclusion Most of the MRSA strains formed biofilm in ica-independent mechanism. fnbB and sarA gene shows higher frequency among the biofilm-associated genes of MRSA, it may infer that most of the MRSA strains biofilm formation are fnbB-mediated. Meanwhile, sarA may be a positive regulator of fnbB, and thus drives the biofilm formation.