Epidemiological analysis of Staphylococcus aureus strains from nasal carriers in a teaching hospital.

The present study was conducted to assess the epidemiological relation of Staphylococcus aureus isolates from nasal carriers of hospital staff. Nasal swabs were taken from each of 327 personnel. After culturing on blood agar for overnight, probable staphylococcal isolates were identified and subjected to tube coagulase test. After a two-week interval, second nasal swabs were taken from the subjects whose first cultures were positive for S. aureus. Nasal carriage was defined in 58 (17.7%) personnel with positive culture for both sampling time. Antibiogram typing and arbitrarily-primed polymerase chain reaction (AP-PCR) with M13 primer were used for typing of the strains. Antibiotyping distinguished seven types and three subtypes, and 85% of the isolates were clustered in one group. AP-PCR, in contrast, identified 12 distinct patterns with 13 variants. A specific profile was not found among the isolates obtained from the personnel in a particular clinic. These results indicate that antibiotyping has poor discrimination power and heterogeneity among the nasal S. aureus strains in the hospital personnel screened is high.