MOLECULAR EPIDEMIOLOGY OF STAPHYLOCOCCUS-EPIDERMIDIS ISOLATES IN A HEMATOLOGICAL UNIT DURING A 4-MONTH SURVEY

In order to study the strain variety, clonal stability and epidemiolog y of Staphylococcus epidermidis, isolates from all bacterial cultures taken when clinically indicated in 2 wards of the hematological unit o f Helsinki University Hospital, during a 4-month period, were characte rized by 3 typing methods: antibiogram, plasmid profile and ribotype. A total of 141 distinct S. epidermidis colonies, from 28 blood culture s and 37 cultures from other sources in 32 patients were studied, Plas mid profiles and ribopatterns revealed 47 different strains of which 1 6 were bacteremic, One of these strains caused bacteremia in 4 differe nt patients over a 3-month period and it was isolated from blood on 7 different sampling occasions. The occurrence of this clone was constan t; it was usually found in both of 2 blood culture bottles inoculated (6/7 pairs) and dominated among the 17 distinct S. epidermidis colonie s studied from the positive bottles (94% of the total). The clones cau sing bacteremias in the 2 wards were distinct. These findings indicate that certain clones of S. epidermidis can predominate in hematologica l wards and that nosocomial transmission of S. epidermidis strains may occur among patients, particularly within the same ward.