Genotyping of methicillin-resistant Staphylococcus aureus isolated from inpatients and medical workers in orthopaedics ward

Abstract

Methicillin-resistant Staphylococcus aureus (MRSA) strains were isolated from the inpatients in orthopaedics ward hospitalized from March 1998 to November 2000, hospital environments, medical workers and the inpatients transferred from TCC (Trauma and Critical Care Center). Genotype by pulsed field gel electrophoresis (PFGE) and biotype according to the production of coagulase, enterotoxin and toxic-shock syndrome toxin-1 (TSST-1) were determined for the MRSA strains to analyze the infection source and transmission route of the infection. Out of 673 S. aureus strains isolated from the inpatients, 390 strains (57.5%) were MRSA. In 89 medical workers in orthopaedics ward, MRSA were isolated in 23 (25.8%) and 7 (7.9%) workers from nasal cavity and hand, finger, respectively. In contrast, no MRSA was isolated from hospital environments. Eighty MRSA strains (80%) from the inpatients and 8 MRSA strains (75%) from the medical workers were shown to have same biotype; coagulase II-enterotoxin C-TSST-1 (+) (II-C- (+)). MRSA strains isolated from the inpatients were grouped into 24 types according to PFGE patterns, and types 17 (17 strains), 12 (13 strains), 1 (8 strains), 4 (8 strains) and 13 (6 strains) were dominant among the MRSA strains isolated. It was shown that MRSA strains with the same PFGE genotype were detected at the same time in the different wards. In addition, MRSA strains isolated from medical workers were all PFGE genotypes 1 and 4. MRSA strain isolated from a new inpatient had a different PFGE type from the 24 kinds of genotype. These results suggest that the involvement of the medical workers might be important as infection source and for transmission of MRSA in hospital.