EPIDEMIOLOGIC TYPING OF COAGULASE-NEGATIVE STAPHYLOCOCCI FROM NOSOCOMIAL INFECTIONS

Biotyping, antibiograms, bacteriophage typing, plasmid profile analysi s and SDS-PAGE protein profiles were used to determine the relatedness of 44 Staphylococcus epidermidis and four S. haemolyticus isolates fr om 14 patients, A selection of these were further characterised by rib otyping, Biotyping classified the isolates into three major groups but was considered a poor strain marker, Although antibiograms classified the S. epidermidis isolates into 20 groups, some changes in the susce ptibility patterns of related isolates from a single patient were demo nstrated, Bacteriophage typing was the least discriminatory of the met hods used, SDS-PAGE gave highly related patterns for the majority of S . epidermidis isolates, Plasmid profile analysis and ribotyping, with a minimum of two restriction endonucleases, were the most discriminato ry methods for typing S. epidermidis. Nonetheless, some isolates from the same patient - probably representing a single strain - varied in p lasmid profile indicating plasmid instability, One of six related isol ates from a single patient lacked two bands from the ribotyping patter n of the other isolates, Although no single method proved entirely sat isfactory on all occasions, the combination of typing methods was suff icient to provide evidence of the relatedness of S. epidermidis isolat es from individual patients.