Clinical occurrence and virulence testing of coagulase-negative staphylococci

A total of 650 coagulase-negative staphylococcal strains of miscellaneous clinical origin were isolated and identified during a 7-year-period. In all kinds of samples Staphylococcus epidermidis was the most frequently found species. In wounds the incidence of haemolytic species (S. cohnii, S. epidermidis, S. haemolyticus, S. simulans, S. warneri) was 79.3%. Among strains derived from male genitals (urethra, semen, etc.) S. epidermidis and S. simulans predominated. Only 8.2% of the strains were found not to harbour resistance determinants, while 63% proved to be multiply resistant. Only the incidence of resistance to oxacillin and first and second generation cephalosporins was low (12.8, 14.9 and 4.5%, respectively). Vancomycin was the only drug effective against all strains. Extracellular slime was produced by 42.2% of the strains. The frequency of slime-positivity among isolates causing clinical infection was twice as high as among contaminations. Slime production seems to be a stable characteristic of the isolates. The comparison of two methods used for detection of slime factor showed that incubation in test tube in Tryptone Soya Broth, or its application to microtiter plates evaluated by photometry are of equal diagnostic value.