Seventeen staphylococci isolated from 54 Slovak local lump cheeses made from ewes’ milk were taxonomically allotted to five species and three clusters/groups involving the following species: Staphylococcus aureus (5 strains), Staphylococcus xylosus (3 strains), Staphylococcus equorum (one strain) Staphylococcus succinus (5 strains) and Staphylococcus simulans (3 strains). Five different species were determined. The aim of the study follows two lines: basic research in connection with staphylococci, and further possible application of the bacteriocins. Identified staphylococci were mostly susceptible to antibiotics (10 out of 14 antibiotics). Strains showed γ-hemolysis (meaning they did not form hemolysis) except for S. aureus SAOS1/1 strain, which formed β-hemolysis. S. aureus SAOS1/1 strain was also DNase positive as did S. aureus SAOS5/2 and SAOS51/3. The other staphylococci were DNase negative. S. aureus SAOS1/1 and SAOS51/3 showed biofilm formation on Congo red agar. However, using quantitative plate assay, 12 strains out of 17 showed low-grade biofilm formation (0.1 ≤ A570 < 1), while five strains did not form biofilm (A570 < 0.1). The growth of all strains, including those strains resistant to enterocins, was inhibited by nisin and gallidermin, with high inhibition activity resulting in the inhibition zone in size from 1600 up to 102,400 AU/mL (arbitrary unit per milliliter). This study contributes to microbiota colonization associated with raw ewe’s milk lump cheeses; it also indicates bacteriocin treatment benefit, which can be used in prevention and/or elimination of staphylococci.

Raw goat milk-derived Lactococcus lactis MK1/3 (CCM 9209) was studied to show its potential for use in the dairy industry. Finding an innovative strain indicates having a new safe, original additive for functional food. The strain has been shown to be safe using a model experiment with Balb/c mice, when no mortality was noted. Its counts were increased continually during 120 days, with the highest value on day 90 (4.38 ± 1.24 colony-forming unit per gram (CFU/g, log 10). In vivo (in the experimental mice), anti-staphylococcal effect was noted with difference 1.82 log cycles. The safety of the strain MK1/3 has been also indicated by the fact that it did not produce damaging enzymes, it has been susceptible to antibiotics, and it has shown low-grade biofilm-forming ability (0.126 ± 0.35). This strain has tolerated bile, and low pH sufficiently. It produced a postbiotic active substance with inhibitory activity against cheese and milk contaminants (Enterococci), reaching antimicrobial activity up to 3200 AU/mL. The count of the strain MK1/3 was higher in yogurts from ewe goat milk (4.66 ± 0.30 CFU/g, log 10), in comparison with its count in yogurts from ewe milk (4.10 ± 0.10 CFU/g, log 10), with no influencing yogurt pH. Its use in 100% starter culture to process fresh cheese based on goat milk was revealed in the standard cheese quality with sufficient amount of lactic acid microbiota. To support the benefit of the strain MK1/3, additional human trials have been reinforced.