Mastitis is a prevalent condition affecting small ruminants, leading to significant economic losses, attributed to decreased milk production and inferior milk quality at a global scale. This issue is particularly pronounced in the rural regions of the Mediterranean, where nearly two-thirds of the world's sheep and a quarter of the global goat milk supply is generated. The present study sought to explore the epidemiology, genetic diversity, antimicrobial resistance profiles, and virulence factors associated with Staphylococcus aureus isolated from sheep and goat suffering from clinical mastitis in Sardinia, Italy.

A total of thirty-four isolates obtained from clinical mastitis cases across 26 dairy farms were characterized through whole genome sequencing and phenotypic assessments of antibiotic resistance.

All isolates were confirmed to be phenotypically methicillin-sensitive S. aureus (MSSA). A small proportion of the isolates exhibited resistance to tetracycline (12.5%) and erythromycin (3.12%). The isolates were categorized into seven distinct sequence types, with ST133 (n = 15) and ST700 (n = 9) being the predominant types. All isolates that were resistant to tetracycline contained either the tetM or tetK gene.

The distribution of certain clusters across various regions demonstrates the ongoing presence of cluster-related infections. Despite all isolates being derived from clinical mastitis cases, they exhibited minimal resistance to the antimicrobials tested. This suggests that the farms surveyed have implemented highly effective hygiene practices, alongside routine antimicrobial resistance testing and the judicious use of antimicrobials to prevent the development of resistance. This approach aligns with the current agricultural regulations, particularly the enforcement of EU legislation. This could result in a reduction in the disease burden and an improvement in animal welfare.