Pattern characterization of genes involved in non-specific immune response in Staphylococcus aureus isolates from intramammary infections

• Ninety-four isolates from 33 different dairy herds were analyzed by microarray.
• Most of the isolates carried genes affecting neutrophil migration.
• S. aureus clonal complexes are related to geographical location.
• Clonal complexes are not related to quarter milk SCC.
• ssl7, ssl11, chip and cap8 genes were associated with an increase of quarter milk SCC.

Staphylococcus aureus isolated from mammary gland are characterized by different genetic patterns. Ninety four isolates from 33 dairy herds were analyzed by the means of a microarray to investigate S. aureus virulence patterns and the distribution of genes believed to be involved in immune evasion. None of the 94 isolates considered were MRSA. However, 50% of the isolates belonged to complexes related to MRSA and to human diseases, while only about 25% of them can be considered as exclusively of bovine origin. The distribution of clonal complexes and the different gene patterns observed confirmed the presence of an influence of geographical localization.The assessment of the influence of genes related to immune evasion on quarter milk cell count showed as four of them showed to be significantly associated to an increase quarter milk SCC. These genes could be potential target for developing new vaccines against S. aureus.