Genetic analysis of methicillin-resistant Staphylococcus aureus from a Western Australian hospital.

The isolates from an outbreak of methicillin-resistant Staphylococcus aureus (MRSA) at Royal Perth Hospital (RPH) during a 3 month period in 1982 have been compared genetically with MRSAs isolated at the same hospital during 1969-1973. The 1982 isolates are genetically similar to isolates from eastern Australia and appear to have been introduced by a patient transferred from a hospital in another Australian state. Methicillin-resistant Staph. aureus isolated during 1969-1973 were genetically distinguishable from the 1982 isolates but were similar to strains reported from elsewhere in the world during these years. This indicates that the MRSA strains currently prevalent in Australia are either a new type or are related to previous MRSAs but have undergone considerable genetic change. These results give further support to suggestions that the strains of MRSA currently being isolated in Australian hospitals have special properties which have facilitated their spread.