Molecular epidemiology of mechicillin-resistant Staphylococcus aureus (MRSA) by pulsed-field gel electrophoresis

Abstract

A total of 103 methicillin-resistant Staphylococcus aureus (MRSA) isolates from patients and 78 MRSA from hospital workers during the years 1990 to 1994, and 52 MRSA from patients in year 2000, in one hospital at Wakayama Prefecture, were typed by pulsed-field gel electrophoresis (PFGE) profiles. MRSA isolates were grouped into 20 genomic types. These types were further divided into 57 subtypes. The type 1 was dominant among patients, and closely related type 1 strains were spread during 1990-1993. In contrast, the type 2 was dominant among medical workers in the same period. In 2000, the type 2 and 4 strains increased, and the diversity and complication of types appeared. The common types between the patients and medical workers were only type 1 to 3. Some strains isolated from both during the same period were shown to have the same types. Others were shown to be patient-specific types. These results suggest that there are complicated transmissions of MRSA in the hospital, i.e., the endogenous infection, patient-patient cross infection and medical worker-patient cross infection.