Antimicrobial Activities of Lactic Acid Bacteria Strains Isolated from Human Breast Milk Against Human Pathogenic Strains

This study aims to screen the antimicrobial activity of lactic acid bacteria (LAB) with probiotic properties isolated from human breast milk. A total of six from twenty five LAB isolated showed clear zone on modified MRS-CaCO3 agar, catalase negative and Gram positive were considered as LAB. All of the six selected isolates were able to tolerance pH 2, 0.3% bile salts for 3h. The antibacterial properties of these isolates against (Escherichia coli, Bacillus subtilis, Staphylococcus aureus and Salmonella typhimurium) were examined using dual agar overlay and microtiter plates methods. Results found that both the cells and supernatants of six selected LAB isolated showed very good inhibitory activity against the target bacteria. The LAB-HM6 isolate showed the highest inhibitory activity (32.0 mm) against S. aureus followed by LAB-HM5 and LAB-HM4 (30.3 mm), then LAB-MH1 (29.3 mm) against S. typhimurium. Supernatant LAB-HM5 caused complete inhibition of all target bacteria, LAB-HM3 inhibited S. typhimurium and B. subtilis, and LAB-HM5 also inhibited the growth of S. aureus during 72 h incubation. Thus, these Lab isolates could be considered as potential antimicrobial probiotic strains human pathogens and should be further studied for their human health benefits