EFFECTS OF DIFFERENT CULTIVATION CONDITIONS ON STAPHYLOCOCCUS AUREUS BIOFILM FORMATION AND DIVERSITY OF ADHESIN GENES

Abstract

ABSTRACTStaphylococcus aureus isolates from foodborne outbreaks were screened for the presence of icaAD, icaBC, clfB, clfA, fnbA, fnbB, ebpS, eno, fib, sasG, sasC, bbp, bap and cna genes that encode microbial surface components recognizing adhesive matrix molecules. All isolates were positive for icaAD, icaBC, fnbA, fib, sasC and cna, and negative for clfA, bbp and bap. The diversity of clfB, fnbB, sasG, eno and ebpS genes was found to exist. It was remarkable that only biofilm‐formation strains were positive for clfB. Furthermore, the effects of the NaCl concentration; glucose, sucrose, lactose and mannitol concentration; pH value; and growth media (Luria broth, basic medium, tryptic soy broth, 7.5% sodium chloride broth and common broth) on S. aureus biofilm formation were compared. Basic medium was proved in favor of biofilm formation. 7.5% sodium chloride broth went against biofilm formation. In detail, different saccharides could effectively promote biofilm formation. Contrarily, the biofilm formation was continuously decreased with increasing NaCl concentration. The effect of pH values on biofilm formation was significant. The rise or drop in pH value (≥12 or ≤4) was directly involved in the decrease in the biofilm formation. Taken together, the biofilm formation of S. aureus influenced by multiple factors and different adhesin genes, which may contribute to biofilm phenotype, possesses diversity.PRACTICAL APPLICATIONSStaphylococcus aureus biofilm formation presents a serious clinical problem. Environmental factor and cultivation conditions contribute a lot to the biofilm development in many S. aureus clinical isolates. Comparing the effect of different cultivation conditions on S. aureus biofilm formation and detecting the presence of different adhesive matrix molecule genes might help clarify the diversity of biofilm formation in foodborne outbreak strains. Applying appropriate sodium chloride solution and proper pH values could be an available way for controlling biofilm formation in S. aureus.