Bacteriocin-like inhibitory substance (BLIS) activity of Streptococcus macedonicus MBF10-2 and its synergistic action in combination with antibiotics

Objective: To characterize the bacteriocin-like inhibitory-substances (BLIS) activity of Streptococcus macedonicus MBF10-2 [named BLIS(MBF10-2)], a bacteriocinogenic strain isolated from an Indonesian tofu byproduct. Methods: BLIS(MBF10-2) was obtained by culturing the bacterium, and standard deferred antagonism assays were used to demonstrate its activity. The antibacterial testing of fractions collected by filtration using 3-30 kDa cut-off membrane sizes were carried out by performing well diffusion method. Results: The growth of Micrococcus luteus, Streptococcus pyogenes, Lactococcus lactis, Leuconostoc mesenteroides and Weissella confusa were inhibited by BLIS(MBF10-2). Interestingly, BLIS-containing fractions obtained from sequential application on ultrafiltration membranes indicated that this bacterium Streptococcus macedonicus MBF10-2 could produces at least two antimicrobial peptides activities, one of which is likely to be a lantibiotic peptide. Potential synergistic activity against certain Gram-positive (but not Gram-negative) species when partnered with antibiotics (ampicillin, tetracycline or kanamycin) were observed. Conclusion: Combination of some BLIS(MBF10-2) active fractions with antibiotics (ampicillin, tetracycline or kanamycin) could demonstrate synergistic activities against certain Gram-positive species.