A comparative study of the anti-listerial activity of smear bacteria

Cell-free supernatants from Staphylococcus epidermidis, Staphylococcus warneri and Brevibacterium linens were found to possess anti-listerial activities. Anti-listerial activities were increased during exponential growth phase and reached a maximum during stationary growth phase. S. epidermidis (SE1) and S. warneri (SW1) were found to have particularly high activities against both Listeria monocytogenes and Listeria innocua as inhibition zones for 48 h cell-free supernatants of these strains were found on average to be approximately 10 times larger than those of B. linens (9174, M18 and BL1). Incubation of 48 h cell-free supernatants from S. epidermidis (SE1) and S. warneri (SW1) with proteolytic enzymes (trypsin and pronase E) resulted in a total loss of anti-listerial activity, which revealed its proteinaceous nature, and thus suggested that the observed anti-listerial activities were due to bacteriocin production. The bacteriocins were found to be relatively heat stable and had a molecular mass higher than 30 kDa.