Serologic typing of Staphylococcus epidermidis biotype 4

Three hundred sixty-five isolates of Staphylococcus epidermidis (coagulase-negative) obtained over a 12-month period from 10 selected wards at New York University Medical Center-Goldwater Memorial Hospital, Roosevelt Island, N.Y., were typed serologically by slide agglutination. The isolates were first biotyped by the Baird-Parker scheme and then subtyped as proteinase-positive or proteinase-negative so that the selection of strains for immunologic study was based on biochemical and enzymatic factors rather than on random choice. The biotyping scheme of Baird-Parker and the differentiation between proteolytic and nonproteolytic strains were of limited in initial categorization of isolates of S. epidermidis. Antisera to proteinase-positive and proteinase-negative S. epidermidis biotypes 1 and 4 were absorbed with different permutations of homologous and heterologous thermostable (TS) and thermolabile (TL) antigens, and four distinct TL and two distinct TS antigenic groups, representing five different serotype patterns (i.e., A1-2, B1-2, C-D1, C-D1-2, and E1), were detected. The TL antigens also appeared to be more widespread and were shared more frequently by strains of S. epidermidis than were TS antigens, but the use of both TS and TL antigens provided a better serologic system than use of either TS or TL antigens alone.