Phenotypic and molecular characterization of community occurring, Western Samoan phage pattern methicillin-resistant Staphylococcus aureus

In New Zealand, it is estimated that greater than half of the methicillin-resistant Staphylococcus aureus (MRSA) strains recovered from patients belong to what has been termed Western Samoan phage pattern types 1 and 2 (WSPP1, WSPP2). These strains differ from classical MRSA isolates in terms of their lack of multiresistance and community occurrence, suggesting that such strains possess properties and/or characteristics different from those of other MRSA. To address this hypothesis, 10 WSPP1 and WSPP2 isolates from Western Samoa, New Zealand and Australia were compared with common hospital MRSA isolates. All WSPP isolates were identical with regard to pulsed-field gel electrophoretic pattern of SmaI-digested DNA, coagulase gene restriction fragment length polymorphism pattern and localization of mecA to a 194 kb SmaI digestion fragment. The WSPP strains were no more resistant/sensitive to various environmental stresses (e.g. skin fatty acids, UV light, desiccation) compared with hospital epidemic MRSA strains, except for their higher tolerance to salt. In terms of virulence, the WSPP MRSA were quantitatively better at attaching to the epithelial cell line HEp2, were uniformly egg-yolk opacity factor negative and produced higher levels of haemolytic toxins compared with non-WSPP MRSA isolates.