Microarray-based characterisation of a Panton-Valentine leukocidin-positive community-acquired strain of methicillin-resistant Staphylococcus aureus

Recent years have witnessed the emergence of novel methicillin-resistant Staphylococcus aureus (MRSA) strains that produce the potent toxin Panton-Valentine leukocidin (PVL). PVL-positive strains can cause complicated skin infections or necrotising pneumonia with high mortality, and these strains have the potential for epidemic spread in the community. In 2004-2005, two case clusters and two isolated cases were observed in eastern Saxony and southern Brandenburg. These were the first known infections with PVL-positive community-acquired MRSA (caMRSA) in this part of Germany. The isolates belonged to agr type III, spa type 44 or spa type 131, and showed a SmaI macrorestriction pattern that corresponded to caMRSA of clonal group ST80. The isolates were susceptible to levofloxacin, macrolides, clindamycin, gentamicin and vancomycin. Most isolates showed resistance to tetracycline and fusidic acid because of the presence of the tetK and far1 genes. A novel plasmid (designated pUB102) harbouring far1, tetK and blaZ was characterised and partially sequenced. Microarray analysis revealed that the caMRSA isolates harboured genes encoding several bi-component toxins (lukF/S-PVL, lukD/E, lukS/F plus hlgA, and another putative leukocidin homologue). Neither tst1 nor genes for enterotoxins A-Y were detected, but the isolates harboured several staphylococcal enterotoxin-like toxin genes (set genes), as well as genes encoding an epidermal cell differentiation inhibitor (edinB) and exfoliative toxin D (etD). Comparative analysis of other isolates from Australia, Germany, Switzerland and the UK showed that these isolates were representative of a widespread clone of caMRSA.