Genetics and epidemiology of methicillin-resistant Staphylococcus aureus isolated in a Western Australian hospital.

Strains of methicillin-resistant Staphylococcus aureus (MRSA) isolated in the Royal Perth Hospital (RPH) in Western Australia have been analysed genetically and three main types were characterized: (i) strains similar to those isolated in Europe before 1973. These strains caused small outbreaks in the RPH during the period 1966-1974, but have not been isolated in recent years, except from one patient with reactivation of osteomyelitis after 16 years; (ii) strains of the type prevalent in eastern and northern Australia, one of which caused a difficult-to-control outbreak in the RPH in 1982. Strains of this type have previously been isolated only from patients who had been in hospitals in eastern and northern Australia, but recently were isolated also from other patients--which indicates that this type of MRSA is now present in the Western Australian community; and (iii) strains, which are genetically different from either of the above two types, were isolated from patients who had been in hospitals in Southeast Asia, but have not yet caused an outbreak in the RPH.