The authors investigated 352 strains of coagulase-negative staphylococci isolated from haemocul- tures of patients with assumed bacteraemia who were hospitalized in standard hospital depart- ments and intensive care units. The strains were identified using STAPHYtest 16 and 14 different species and subspecies of coagulase-negative staphylococci were found. Most frequent were strains of Staphylococcus epidermidis (53%), strains of S. hominis subsp. hominis (22%) and S. haemolyticus (13%). In the strains the production of slime and delta-haemolysin was investigated. The formation of these two important factors of virulence was recorded in 95% strains (incl. major slime production in 13.4%), and 50% strains resp. The resistance to 13 antibiotics was also assessed. A total of 91% strains were resistant to penicillin, 63% to oxacillin and amoxicillin with clavulanic acid, 67% to gentamicin and 66% to erythromycin. In the group 15 strains of a recently described subspecies S. hominis subsp. novobiosepticus was identified. These isolates displayed most frequently resistance: they were resistant in 100% to five antibiotics (penicillin, oxacillin, erythromycin, clindamycin and amoxicillin with clavulanic acid) and with a single exception to another three antibiotics (chloram- phenicol, gentamicin and ciprofloxacin). In these strains most frequently slime as well as delta-hae- molysin was found. The authors assume, consistent with previous work, that it is important to focus attention on the incidence of strains of S. hominis subsp. novobiosepticus which very probably play an important role as agents in hospital infections. The authors describe also detection of one strain of S. cohnii subsp. urealyticum which was resistant to 10 of 13 antibiotics. The authors are convinced that also classical phenotypic analysis can contribute in an effective manner to the solution of the problem of infections caused by coagulase-negative staphylococci.

        Key words: coagulase-negative staphylococci – virulence factors – resistance to antibiotics – S. hominis subsp. novobiosepticus – infection of the blood stream.