Analysis of the biofilm formation and icaA genes of Staphylococcus epidermidis isolates / 中华微生物学和免疫学杂志

ABSTRACT

Objective To determine the ability of biofilm formation of Staphylococcus ephtermidis isolates and analyze the correlation between the icaA gene and its expression and biofilm formation. Methods Collecting 205 Staphylococcus epidermidis isolates identified with normal laboratory tests (coagulase-negative, biochemical identification, polymyxin-resistant and novobiocin-sensitive ), the suspected isolates were con-formed with API-Staph. Biofilm production was assessed by incubating the strains on Congo Red Agar (CRA) plates and quantitative biofilm production determined by a 96-well tissue culture plate and biofilm morphous were detected by scanning electron microscope ( SEM ) ; Amplifying partial fragments of icaA genes with PCR; Analyzing the expression levels of icaA gene with RT-PCR through Bio-Rad system and Quantity One software. Results 24 isolates showed positive in CRA tests, 22 isolates were positive in semiquantita- tive adhesion assays and 28 isolates existed icaA gene among 205 isolates of Staphylococcus epidermidis. The icaA-positive strains demonstrated biofilm formation (microcolonies on silica films ) while icaA-negative strains only adhered as individual cells under scanning electron microscope. All 22 strains which showed positive in semiquantitative adhesion assays harbored the icaA gene. The expression levels of icaA gene with RT-PCR in 6 Staphylococcus epidermidis isolates showed a higher tendency in 4 strains which demonstrated positive in semiquantitative adhesion assays than 2 negative strains in semiquantitative adhesion assays. Conclusion The isolations of Staphylococcus epidermidis have the abilities of forming biofilm, and the icaA gene and its normal expression is the important molecular biology foundation of biofilm formation. Other fac-tors maybe involve in the expression of icaA gene in Staphylococcus epidermidis isolates.