Identification of new staphylococcins with potential application as food biopreservatives

In this study, 47 staphylococcal strains, isolated from milk of mastitic cattle from Brazilian dairy herds, were tested for antimicrobial substance (AMS) production. Fourteen strains were shown to produce AMS. Most AMS were sensitive to proteolytic enzymes, suggesting that they might be bacteriocin-like inhibitory substance (BLIS). BLIS 4059, 4231, 4244, 5409, and 5580 exhibited a broad spectrum of activity and, therefore, were selected for further studies. The five BLIS+ strains were identified to the species level: 4059 and 4231 as Staphylococcus aureus, 4244 and 5409 as Staphylococcus hyicus, and 5580 as Staphylococcus epidermidis. Cross-immunity analysis and detection of the aurABCD operon by PCR and DNA/DNA hybridization revealed that strains 4059 and 4231 produce BLIS either identical or similar to aureocin A70 and encoded on plasmids with a size similar to that of pRJ6 (7.9 kb). A structural gene similar to those of epidermin and Bsa was detected in the genome of strain 5409. The BLIS+ strains 4244 and 5580 produce BLIS that seem to be distinct from the best characterized staphylococcal bacteriocins described in the literature. The BLIS produced by S. hyicus 4244, hyicin 4244, had the ability to inhibit all 30 strains tested as targets, including food-borne pathogens, such as Listeria monocytogenes and S. aureus. Both pathogens were also inhibited in a food matrix, suggesting that hyicin 4244 has potential biotechnological application as a food biopreservative.