PHENOTYPIC CHARACTERIZATION OF EPIDEMIC VERSUS SPORADIC STRAINS OF METHICILLIN-RESISTANT STAPHYLOCOCCUS-AUREUS

Forty strains of methicillin-resistant Staphylococcus aureus (MRSA) were divided on the basis of their epidemiologic behavior into two subgroups, sporadic MRSA (SMRSA) and epidemic MRSA (EMRSA) strains, The strains were examined for binding of I-125-labelled fibronectin, vitronectin, collagen, Fc fragments of immunoglobulin G, and fibrinogen, A significant difference between EMRSA and SMRSA strains was found for binding of I-125-labelled fibrinogen and for Fc fragments of immunoglobulin G, (P < 0.05), No significant difference in the binding of I-125-labelled fibronectin and collagen was found between EMRSA and SMRSA strains, The binding I-125-labelled vitronectin to MRSA strains was found to be aspecific, Capsular serotypes of the strains were determined with monoclonal antibodies against capsular types 5 and 8, Strains could be divided into the following four groups: types 5, 8, and 5/8 and nontypeable, More nontypeable strains were found in the EMRSA group (66.6%), Significantly more EMRSA strains (79%) than SMRSA strains (44%) produced alpha-toxin (P < 0.025), Logistic regression analysis using a combination of the parameters I-125-labelled immunoglobulin G binding, capsular type, and alpha-toxin production predicted the epidemic character with a sensitivity of 83% and a specificity of 75%.