Association of a lukM-positive clone of Staphylococcus aureus with fatal exudative dermatitis in red squirrels (Sciurus vulgaris)

Fatal exudative dermatitis (FED) is a recently described condition affecting red squirrels (Sciurus vulgaris) on the Isle of Wight and Jersey (Simpson et al., 2010a). Staphylococcus aureus strains isolated from skin lesions in cases of FED were characterised by molecular and phenotypic approaches. The strains were found to belong to a single MLST clonal complex (CC49) representing either ST49 or a novel single locus variant thereof (ST1957), were closely related by other molecular typing approaches, and all possessed the leukotoxin M encoding gene (lukM). In contrast S. aureus was either not isolated from none-FED cases or belonged to distinct and diverse molecular types that, with one exception, did not encode lukM. All isolates from FED cases were susceptible to all antimicrobials tested, including penicillin, and all proved negative for mecA and mecC as well as 14 other staphylococcal toxin genes. As all squirrels affected by FED were infected with S. aureus of the same lineage and encoded the lukM gene, it is possible that strains of this lineage may be involved in the pathogenesis of the dermatitis.