Espersen, F., Hertz, J. B. & Hsiby, N. Cross-reactions between Staphylococcus epidermidis and 23 other bacterial species. Acta path. microbiol. scand. Sect. B, 89: 253-260, 1981. By quantitative immunoelectrophoretic methods, 43 antigens were found in a mixture of sonicated preparations of four Staphylococcus epidermidis strains, using corresponding rabbit antiserum. Two of the antigens were identified as cell wall teichoic acid and a peptidoglycan antigen, respectively. Using this antigen/antibody reference system, cross-reactions between S. epidermidis antigens and antigens from other bacterial species were investigated. Fourteen of the S. epidermidis antigens cross-reacted with antigens from all S. aureus strains investigated. Only few cross-reactions were found between S. epidermidis and bacteria not belonging to the Micrococcaceae. The antigenic relatedness, expressed as a matching coefficient, seems promising for taxonomic work.The antigenic structure of S. epidermidis has been investigated by different methods ( I , 8, 12, 14, 32).Most investigators have focused on teichoic acid and peptidoglycan antigens found in the cell wall; other antigens have received less attention. Characterization of the antigens of this organism would seem to be important because of its increasing significance in human infections.The purpose of the present study was to investigate the antigenic components of S. epidermidis by quantitative immunoelectrophoretic techniques and to study cross-reactivity of S. epidermidis with other bacteria, especially other Micrococcaceae.
MATERIALS AND METHODSStrains. Four Staphylococcus epidermidis strains, representing the four biotypes of Baird-Parker (41, were chosen as reference strains. AU were isolated from blood cultures of patients with bacteraemia. The strains were provided by Dr. K. Rosendal, Statens Seruminstitut, Copenhagen, who also performed the biotyping. The main biochemical characteristics of these strains are given in Table I .The origin of many of the other bacteria shown in Table 3 have been described previously (18, 31). The collection strains of Micrococcaceae, NCTC (National Collection of Type Cultures, London) 4163,8532, 761 2 and 7292; CCM (Czechoslovak Collection of Microorganisms, Brno) 901 and 385; ACBP (Dr. A . C. Baird-Parker, England) 3, 5 and 9, were provided by Dr. N . Mortensen, Institute for Medical Microbiology, University of Copenhagen. Cowan 1-111, Wood 46 and S. aureus strains belonging to the 4 phage groups (Collection numbers E 237 I , E 2476, E 1346 and E 1430) were provided by Dr. K. Rosendal, Statens Seruminstitut. Peptococcus micron and Clostridium perfringens were provided by Dr. M. Tvede, Statens Seruminstitut.Antigens. Antigens for immunoelectrophoretic experiments were obtained by sonication (18). Reference antigen (Ref. Ag.) was a mixture of equal volumes from each reference strain, the colloid concentration was 6.9 g/l (refractometry, using human IgG as standard).Antigens for investigation of heat-stability were prepared by autoclaving Ref . A...