GENOTIPIZZAZIONE DI S. AUREUS ISOLATI DA LATTE BOVINO DI AZIENDE LOMBARDE

Staphylococcus aureus strains (n=1559) isolated from North Italian dairy herds were genotyped by RS-PCR. A selection of these strains (84 from bulk tank milk and 91 from individual cow milk) was also analyzed for the presence of adlb gene, which is considered a possible marker of contagiousness. The adlb gene amplification was included in a multiplex PCR also targeting nuc and mecA genes. RS-PCR identified 83 different genotypes combined into 48 genotypic clusters, among which genotype B with his variants (GTB) was the most prevalent (n=491). A clonal diffusion of a single genotype was shown in most farms (373/458), especially when GTB was involved. Most of Staph. aureus belonging to GTB carried the adlb gene (38/43), as well as very few strains belonging to a different genotype. When investigated, all of them were associated with high prevalence in the herds, confirming that RS-PCR and adlb PCR could be useful tools in predicting the clinical properties of isolates.