Molecular Epidemiology of Staphylococcus aureus Isolates from Horses by Pulsed-Field Gel Electrophoresis

Pulsed-field gel electrophoresis (PFGE) analysis was used to type 98 strains of Staphylococcus aureus isolated from horses. Fifty-three metritis strains in the Hidaka district of Hokkaido between 1985 and 1991 produced 12 different patterns (A-L). Various genotypes of S. aureus have been found to be involved in metritis, but the same few genotypes of S. aureus were isolated repeatedly from metritis in that period. Ten dermatosis strains in Ibaraki Prefecture between 1985 and 1988 produced 2 patterns (D and G1). The 2 patterns were also found in isolates from metritis. Thirty-five strains obtained from the penis swabs of 7 stallions (5 strains/horse) at one stud farm in the Hidaka district in 1998 belonged to a very closely related group; these strains appear to have originated in a common source. Interestingly, the PFGE patterns of the penis strains were similar to the pattern D observed in both metritis and dermatosis. These results demonstrated the usefulness of the PFGE method for epidemiological investigations of S. aureus.