Changing epidemiology of methicillin‐resistant Staphylococcus aureus in Western Australia

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Abstract
Objective To assess the epidemiology of methicillin‐resistant Staphylococcus aureus (MRSA) in Western Australia. Design Retrospective review of statutory notification data. Setting Western Australia (WA), 1993. Outcome measures Notification rates, antibiotic resistance patterns and classification of isolates as imported or WA MRSA strains on the basis of antibiotic susceptibility. Results There were 204 notifications of MRSA, 78% of which were classified as WA MRSA. Three outbreaks of MRSA infection and colonisation occurred in separate WA hospitals. otification rates per 100000 were highest in the rural regions: the Kimberley (86.32), Goldfields (62.47), Mid West (37.21) and Pilbara (27.38) regions; and lowest in the metropolitan regions (5.52). All MRSA isolates were susceptible to vancomycin. Most imported strains were susceptible to amikacin, bacitracin, chloramphenicol, framycetin, fusidic acid and novobiocin, but only 23% to gent amicin. WA MRSA strains remained predominantly susceptible to all antibiotics tested, except 8‐lactams, erythromycin and tetracycline, but a few strains resistant to rifampicin (1%) and fusidic acid (3%) appeared in the second half of 1993. Conclusions The epidemiology of MRSA in WA is changing rapidly, with increases in both the numbers of notifications and the proportion from country regions. A new strain of MRSA (WA MRSA) that is less resistant to antibiotics than imported MRSA has emerged and is threatening the State's success in preventing establishment of MRSA in its hospitals.