Commensal coagulase-negative Staphylococcus from the udder of healthy cows inhibits biofilm formation of mastitis-related pathogens

•The native microflora plays an important role in the maintenance of udder health.•Commensal Staphylococcus chromogenes LN1 inhibits biofilm formation of mastitis pathogens.•Anti-biofilm supernatant does not affect bacterial growth of pathogenic strains.•Anti-biofilm doses of LN1 cell-free supernatant do not affect bovine cell viability.•Staphylococcus chromogenes LN1 shows biotechnological potential for mastitis treatment.

Bovine mastitis, considered the most important cause of economic losses in the dairy industry, is a major concern in veterinary medicine. Staphylococcus aureus and coagulase-negative staphylococci (CNS) are the main pathogens associated with intramammary infections, and bacterial biofilms are suspected to be responsible for the persistence of this disease. CNS from the udder are not necessarily associated with intramammary infections. In fact, some commensal CNS have been shown to have biological activities. This issue led us to screen exoproducts from commensal Staphylococcus chromogenes for anti-biofilm activity against different mastitis pathogens. The cell-free supernatant from S. chromogenes LN1 (LN1-CFS) was confirmed to display a non-biocidal inhibition of pathogenic biofilms. The supernatant was subjected to various treatments to estimate the nature of the biofilm-inhibiting compounds. The results showed that the bioactive compound >5 KDa in mass is sensitive to thermal treatment and proteinase K digestion, suggesting its protein properties. LN1-CFS was able to significantly inhibit S. aureus and CNS biofilm formation in a dose-independent manner and without affecting the viability of bovine cells. These findings reveal a new activity of the udder microflora of healthy animals. Studies are underway to purify and identify the anti-biofilm biocompound and to evaluate its biological activity in vivo.