Selection Of Some Lactobacilli And Bifidobacteriastrains As Potential Probiotic Cultures

The in vitro and in vivo roles of Lb. acidophilus ATCC 4356, Lb.johnsonii ATCC 33200 and B. bifidum ATCC 15696 were investigated to explore their potential to survive transit through gastrointestinal tract and to inhibit coliform. These three cultures were tested, in vitro, for tolerant gastric and intestinal juices, they exhibited acceptable levels of survivability ranged from 93.95% to 98.75% and from 84.07% to 94.48% ingastric and intestinal juices respectively.
            Short-term administration (2h) of the three tested strains in chicks, in vivo, confirmed their efficacy to passage successfully through the gastrointestinal tract. Also, B. bifidum ATCC 15696 recovered from the small intestine showed the least decrease in count after 2h of feeding and ranked the highest survival %, being 90.41%.
            Moreover, the tested cultures were also examined in coculture withE. coli O157:H7ATCC 51657 in skim milk medium for their antagonistic effect. Results obtained showed that B. bifidum ATCC 15696 exert strong inhibitory activity toward E. coli, followed by Lb. acidophilus ATCC 4356. This statement may be attributed to the production of antimicrobial agents.
            In addition, feeding experiment had carried out, in vivo by using Fayomy chicks to evaluate the antagonistic activity of the tested cultures towards E. coli during their passage through the gastrointestinal tract. The coadministration of E. coli and B. bifidum ATCC 15696 resulted in the decrease in E. coli count in feces samples, being 58.75%, followed by Lb. acidophilus ATCC 4356, actually 57.22%.
            Generally, the obtained results strongly suggest that the tested strains were considered resistant to gastrointestinal transit, and this observation coupled with their good gastric and intestinal juice tolerance. Continuously, these cultures were able to inhibit E. coli in both coculture and intestines of chicks. The effect are seen in a short period (72h), suggesting that these cultures may have clinical application for people suffering from gastrointestinal disorders caused by coliforms.