Nisin and lysostaphin activity against preformed biofilm of Staphylococcus aureus involved in bovine mastitis.

Abstract

The biofilm produced by Staphylococcus aureus isolates involved in clinical or subclinical bovine mastitis and the activity of nisin and lysostaphin against the preformed biofilm produced by these strains were investigated. Eighteen strains were tested and all produced biofilm. Eight strains with distinct biofilm composition were selected for the antimicrobial activity assays. The minimal inhibitory concentration of each bacteriocin was determined against the planktonic cells and ranged from 15·6 to 500μgml(-1) for nisin, and from 3·9 to 50μgml(-1) , for lysostaphin. Lysostaphin treatment (0·4μgml(-1) ) for 4h caused a strong Staph.aureus 4181 biofilm detachment and death of the majority of the sessile cells, while nisin treatment (100μgml(-1) ) for the same time caused only a great reduction in cell viability. Additionally, combination of both bacteriocins for 4h resulted in significant death of the sessile cells but no biofilm detachment. The treatment with lysostaphin alone or in combination with nisin was effective in killing most biofilm sessile cells. The action of lysostaphin, either alone or in combination with nisin, against established staphylococcal biofilm may represent an alternative to bovine mastitis control. However, the duration of the treatment should be considered for its application so that the best effectiveness can be achieved.