A decade of community MRSA in New Zealand.

In 1992, isolates with a distinctive phage pattern were identified amongst the 186 MRSA recovered in New Zealand. These unusual isolates were recovered in the Auckland region from individuals who came from or had visited Western Samoa, and were called Western Samoan phage pattern (WSPP) MRSA. They were almost exclusively community based and were mainly responsible for the alarming 15-fold increase in MRSA seen in New Zealand over the next 6 years. Since 2000, the number of infections attributable to WSPP MRSA appears to be declining. WSPP isolates are clonal, possess a unique type IV SCC mec element, and a distinctive multilocus sequence allelic profile (ST30). WSPP isolates are invariably not multiresistant with methicillin MICs generally <or=32 microg/ml. Virulence of the WSPP clone appears to be related to its adhesive and consistent toxin- (e.g. Panton-Valentine leukocidin, alpha- and gamma-haemolysins) producing capabilities. Isolates are most frequently associated with cutaneous lesions in younger age groups. Since 1998, MRSA isolates belonging to the UK-derived EMRSA-15 strain (also type IV SCC mec) have continued to increase in New Zealand, and together with WSPP, these strains now dominate MRSA isolations in New Zealand.