224 coagulase-negative strains of staphylococci (CNS) isolated from haemocultures of hospitalized patients were classified finto 11 types. The most frequent one was S. epidermis (73.2 %), S. haemolyticus (7.6 %), S. lugdunensis (6.7 %) and S. hominis (3.6 %). In different strains virulence factors were assessed: production of mucus and delta toxin. Based on these properties the strains were classified finto biotypes. Of 164 strains of S. epidermis mucus was produced by 64.6 % and delta toxin by 75.0 %. Of 17 strains of S. haemolyticus mucus was produced by S and delta toxin by 10 strains. Of 15 strains of S. lugdunensis 9 strains produced both virulence factors. Of S strains of S. hominis 5 strains produced mucus and 3 delta toxin. In strains S. capitis, S. sciuri, S. auricularis, S. caprae these factors were not detected. The most frequent biotypes were: subtype 3 (43.3 %), la (26.8 %) and lb (10.3 %). The sensitivity of CNS to 11 antibacterial substances was assessed quantitatively by estimating the MIC (mg/1). The most effective antibiotic was vancomycin (100 %) and tetracycline (76.8 %). Only 26.3 % strains were sensitive to oxacillin and cefalotine. Of 224 CNS (70 %) were resistant to more than S antibacterial substances.

        Key words: coagulase-negative staphylococci - virulence factors - sensitivity to antibacterial substances.