Aureocin A70 production is disseminated amongst genetically unrelated Staphylococcus aureus involved in bovine mastitis.

Aims:  The main aim of this study was to analyse the genetic relationship amongst 46 Staphylococcus aureus Bac+ strains isolated in Brazil from 12 geographically distant dairy herds, including 34 isolates that produce the antimicrobial peptide aureocin A70. Methods and Results:  The comparison of 46 Staph. aureus Bac+ strains was performed by pulsed-field gel electrophoresis (PFGE). Thirteen different pulsotypes were identified, and the subtype A1 was the most prevalent one. Nine strains belong to pulsotype F, the second most prevalent and mostly confined to a single herd. The PFGE patterns of the 34 Staph. aureus aureocin A70-producers, isolated in Brazil, were also compared with those of strains isolated from bovine mastitis cases in Argentina and revealed that these strains are not genetically related. Conclusions:  Although a previous study has suggested that a prevalent pulsotype of aureocin A70-producer Staph. aureus involved in bovine mastitis is disseminated in Argentina, this does not occur in Brazil. Additionally, it was possible to demonstrate that closely related staphylococcal strains can produce distinct staphylococcins. Significance and Impact of the Study:  This study corroborates the hypothesis of horizontal gene transfer of aureocin A70 genes amongst distinct staphylococcal strains involved in bovine mastitis, giving them a selective advantage when colonizing the mammary glands.