Abstract

Lactic acid bacteria (LAB) present many important properties in food manufacturing, such as improvement of physical characteristics and the production of lactic acid that aids in the increase of the shelf life of food products. Also, LAB can suppress growth of pathogens, control of serum cholesterol level, modulate immune system, and improve lactose digestion. Five standard (Lactobacillus paracasei, Lactobacillus helveticus, Lactobacillus fermentum, Bifidobacterium longum and Lactococcus lactis) lactic acid bacterial strains were screened for probiotic potential properties and their ability to antagonize the growth of some enteric pathogens isolated from patients suffering from acute gastroenteritis. The five strains of LAB were resistant to acidic pH and bile salts. Lactobacillus strains showed protein and starch digesting capability on agar plate while B. longum ATCC 15707 and L. lactis subsp. lactis ATCC 11454 showed only protein digestion. In addition, Lactobacillus strains showed antagonistic effects against all pathogenic strains tested. L. paracasei and L. helveticus [culture and cell-free culture supernatant (CFCS)] exhibited the highest antagonistic activity against the tested pathogens followed by L. fermentum. While B. longum and L. lactis subsp. lactis showed weak or no activity against the tested strains. L. paracasei, L. helveticus, and L. fermentum showed potential to be used as probiotic strains with considerable good antagonistic activity against the most important enteric pathogens.

Key words: Lactobacillus paracasei, Lactobacillus helveticus, Lactobacillus fermentum, Bifidobacterium longum subsp. longum, Lactococcus lactis subsp. lactis, potential probiotic, antagonistic activity.