Relationship between adhesin genes and biofilm formation in vancomycin-intermediate Staphylococcus aureus clinical isolates.

The adherence ability and biofilm production are the characteristic of enhanced virulence among isolates of vancomycin-intermediate Staphylococcus aureus (VISA) strains. Although biofilm-forming properties have been well demonstrated in S. aureus, they still remain unclear among the recently emerged types of VISA strains. The aim of this study was to investigate correlations between the distribution of genes encoding staphylococcal microbial surface components which recognise adhesive matrix molecules (MSCRAMMs), the surface protein A (Spa) types, MLST types and the ability of VISA strains to biofilm formation. Microtiter plate assay (Mtp) results showed that all eleven biofilm producer isolates were adherent at various levels. PCR experiments showed that nine MSCRAMM genes, clfA, clfB, fnbA and fib were detected in all of the strains, indicating a high prevalence. The prevalences of other MSCRAMMs and icaABCD genes were found to be variable and not equally distributed among the VISA strains. There was no direct correlation between the distribution of adhesion-related genes and biofilm formation, which indicates that the presence or absence of these genes cannot be employed as an indicator of the ability to biofilm formation. Isolates which belong to the same Spa and ST types showed similar adherence capacities in the Mtp assay, but significant differences were observed between different Spa types. The findings of this study, using quantitative methods, have shown that genotypically different strains of VISA have different capabilities to produce biofilms. This may be caused by a difference in the spa types of VISA isolates or due to their differences in the expression of MSCRAMM and icaABCD genes.