Variation of Coagulase-Negative Staphylococci in the Skin Flora of Healthy Individuals during One Year

In order to investigate the variation and turnover time of coagulase-negative staphylococci (CNS) in the skin flora and whether CNS strains were transmitted over the body, we studied CNS in the skin flora of seven healthy persons during a period of one year. From 134 samples, collected approximately monthly, 547 CNS were isolated. All isolates were typed by PhP-CS, a biochemical fingerprinting method and, if further discrimination was required, also by pulsed-field gel electrophoresis of DNA. We found 109 different strains out of which 63 % were transient, i.e. isolated only once, but the majority (77%) of isolated CNS belonged to resident strains, isolated at least twice. The CNS flora of the toes showed a high variation compared to the nares and axillas. Eighty percent of the resident strains colonized the skin for more than three months and two strains were isolated during the whole study period. Different strains were normally found on different persons, although several persons belonged to the same households. Transmission over the body of the same strain is very uncommon. It is concluded that although many different strains can be found on a body location, most of them are only found occasionally. However, certain strains may colonize the skin and become permanent members of the normal flora. Key words: colonization, coagulase-negative staphylococci, skin flora. ORIGINAL ARTICLE