Methicillin-resistant Staphylococcus aureus and Staphylococcus pseudintermedius detected in the BfT-GermVet monitoring programme 2004-2006 in Germany

Objectives: During recent years, methicillin-resistant Staphylococcus aureus (MRSA) strains from animals have become the focus of various studies. In the present study, coagulase-positive staphylococci obtained from pigs, dogs and cats suffering from acute infections, which had been collected in the BfT-GermVet monitoring programme in Germany and phenotypically identified as oxacillin-resistant, were characterized. Methods: The staphylococci were comparatively investigated for their resistance phenotypes and genotypes. Resistance genes were identified by PCR. MRSA strains were further characterized by SmaI macrorestriction analysis and spa typing to assess their genomic relationships. Results: Among the 248 strains tested, 7 strains (5 porcine S. aureus and 2 canine Staphylococcus pseudintermedius) carried the resistance gene mecA. Gentamicin resistance was based on the presence of the gene aacA/aphD while three different tetracycline resistance genes, tet(K), tet(L) and tet(M), alone or in combinations, were detected. The single macrolide/lincosamide-resistant strain carried an erm(A) gene. All MRSA strains proved to be non-typeable by SmaI macrorestriction analysis and exhibited the spa types t011 (four strains) or t034 (one strain). Conclusions: Based on their spa types and their non-respondence to SmaI digestion, all five porcine MRSA strains resembled MRSA strains of multilocus sequence type ST398, previously detected among pigs in neighbouring countries such as The Netherlands or Denmark. The results of this study indicate that such strains are also involved in defined disease conditions of pigs from various parts of Germany.