Virulence-associated genes of Staphylococcus aureus isolates from soft tissue infections in Alpine chamois

Background S. aureus virulence pattern, antimicrobial resistance profile and host specialization are of great concern in domestic animals that can act as reservoir or transient carriers of zoonotic (1) and human strains (2). Concerning free-living wild ruminants a low prevalence of methicillin resistant S. aureus (MRSA) was recently reported in healthy Iberian Ibex (Capra pyrenaica hispanica) and red deer (Cervus elaphus) (3). Materials and methods S. aureus isolates were obtained from a convenience samples of two subjects that were euthanized by gamekeepers due to walking impairment and painful status in north-western Italian Alps (Verbano Cusio Ossola province) in autumn 2011. The subjects, a kid and a three year old male, showed good body condition and a regular process of molt. The post-mortem examination confirm a good kidney fat deposit and regular contents of stomach compartments. No macroscopic lesions were observed in the kid. Acute fibrinous pericarditis, liver steatosis and an enlarged retromandibular lymph node affected by an abscess were observed in the adult chamois. Samples for bacteriological analysis were swabs collected from kid nasal cavities and organs (brain, lung, liver, spleen and kidney) and from adult's abscess. PCRs were performed on S.aureus isolates targeting virulence-associated genes using protocols described previously [nuc, sea, sec, sed, seg, seh, sei, sej, sek, and sel (4); coa, clfA, spa, tst, seb, see, eta, and etb (5); leukE (6); LukS-LukF/PV (PVL) and mecA (7); sak, fmtB, scn, and chp (2); LukE-LukD and LukM (8); cna (9)]. Results and discussion S. aureus soft-tissue infections were interestingly observed in both subjects and a colonization of nasal mucosa was also confirmed. Actually, S. aureus was isolated from nasal mucosa and liver of the kid and from the abscess of adult chamois. A large set of enterotoxin toxin genes (sea, sec, seg, sei, sel), rare in domestic ruminants (10; 6; 11), were identified from S. aureus isolates, harbouring from two (nasal, abscess isolates) to five different genes (liver isolate). The abscess isolate was also positive for leukotoxin and toxic shock syndrome toxin (tst) genes. None of the isolates harbored genes encoding for exfoliative toxins A and B (eta, etb) and Panton-Valentine Leukocidin (LukS-LukF/PVpvl). All S. aureus isolates were positive for spa, coa, leukE, clfA, nuc, fmtB, cna, sak, scn and chp genes. To our knowledge data on S. aureus virulence pattern have never been recorded in chamois and in other wild ruminants to which our data can be compared. However, immune evasion gene cluster, rare in animal isolates and highly prevalent in human ones (2) was detected in all the isolates. A great matter concerns the positivity to tst gene, located, with sec and sel genes, on mobile genetic element called pathogenicity island, coding for a toxin that damages host tissues and provokes toxic shock syndrome in humans. Overall, though the data from this study are inadequate to draw any association between the S. aureus virulence profile and the clinical debility of the animals, peculiar and rare virulence profiles were detected. Perspective and future priorities The antimicrobial resistance profile and genotype characterization of the isolates are ongoing. A wider number of isolates from wild and domestic species will be investigated to understand host specificity and to assess the zoonotic or anthropo-zoonotic potential of S. aureus. Acknowledgements We wish to thank the Corpo di Polizia Provinciale di Verbania and Ente Parco Nazionale Val Grande for field support. References 1.Huijsdens X.W., van Dijke B.J., Spalburg E., van Santen-Verheuvel M.G., Heck M.E., Pluister,G.N., Voss A., Wannet W.J., de Neeling A.J. 2006. Community-acquired MRSA an