Antimicrobial activity and adhesion ability of indigenous lactic acid bacteria isolated from goat milk

To be categorized as probiotic bacteria, lactic acid bacteria (LAB) must have at least antimicrobial activity and adhesion ability on intestinal mucosal surfaces. The aim of this study was to determine the antimicrobial activity and adhesion ability of eight LAB strains isolated from goat milk. The isolates passed initial selection on low pH (2.0, 2.5, and 3.0) and bile salt tolerance (0.3% Oxgall). Three strains of L. rhamnosus (TW2, TW3, TW32); five strains of L. plantarum (TW4, TW10, TW14, TW26, and TW28) were examined for their antimicrobial activity against both spoilage and pathogenic bacteria (S. Typhimurium ATCC 14028, E. coli ATCC 8739, B. cereus ATCC 13061, S. aureus ATCC 25923 and P. aeruginosa ATCC 9027). Five isolates (TW2, TW4, TW14, TW28, and TW32) were evaluated for their ability to adhere to intestinal mucosal surfaces. A modified well diffusion method was used to assess the antimicrobial activity. A modification of an animal model was also used to analyze the LAB adhesion ability. The adhesion of the bacteria on jejunum and ileum was examined by using Scanning Electron Microscope. The result showed that the isolates had diameters of inhibition ranging from 12.6 to 19.9 mm for S. Typhimurium, 11.3 to 21.4 mm for E. coli, 7.5 to 19.9 mm for B. cereus, and 9.9 to 24.7 mm for P. aeruginosa. L. plantarum TW10 and TW26 had no inhibition activity for S. aureus. The adhesion ability of the bacteria was 0.54-2.19 log CFU/ cm2 on the intestinal mucosal surfaces. The highest adhesive level in jejunum and ileum was showed by L. rhamnosus TW2.