[Formation of biofilm by slime producing Staphylococcus epidermidis and bactericidal activity of cefazolin]

Slime production was studied in a total of 598 strains of Staphylococcus aureus and 11 species of coagulase negative staphylococci and the relationship of the slime production and biofilm formation was investigated. The high slime production was obtained in 42 of 263 strains (16%) of S. epidermidis only. The adherence of S. epidermidis to biomedical silicone discs (S discs) and biofilm formation were investigated in vitro in high slime producing and non-producing strains. The adherence rates of S. epidermidis to the S discs ranged from 2.3 to 14.8%. There was no relationship between slime production by S. epidermidis and the adherence rates. Biofilm was formed only in slime producing strains with cell growth on the S discs when they were incubated. The process of the biofilm formation was obtained by scanning electron microscopy; there were many projections, probably slime secreted from the cells, on the cell surface, and picture showing agglutination of cell by crosslinking. The bactericidal activity of cefazolin, cefmetazole and flumoxef against S. epidermidis after formation of the biofilm decreased more markedly than that before formation. Cefazolin reduced the number of S. epidermidis and eliminated the formed biofilm in an in vitro simulation model of serum concentration in human after drip infusion of 2 g of cefazolin.