Identification of commensal lactobacilli with immunomodulatory activities and inhibitory effects on Salmonella colonization in chickens

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Lactic acid producing bacteria (LAB) are a group of microbes that can be found in the intestines of mammals and avian species. Several LAB, including lactobacilli have been found to have probiotic activities. Some lactobacilli are normal members of the intestinal community of microbes and confer upon their host health benefits. These health benefits include control of disease-causing enteric microbes and enhancement of host immune response, both systemically and also locally in the intestine. In the poultry industry, some practices, such as the prophylactic use of antibiotics, alter the composition of the intestinal microbial community and may limit the ability of commensal microbes to control disease-causing microbes, such as Salmonella. In fact, poultry products are a major source of food-borne disease for humans. In Canada, Salmonella caused about 5,200 reported cases of food-borne illness in 2004, with an average estimated cost of $1,100.00 per reported case in 2001-02. It should also be noted that based on some estimates, the number of unreported cases of salmonellosis is 10 times higher than the number of reported cases. Therefore, it has become urgent for the poultry industry to develop strategies for control of transmission of food-borne pathoegens from poultry to humans. Probiotics containing lactobacilli offer one such strategy. In addition to the effects of probiotics on control of enteric pathogens, lactobacilli possess immunomodulatory activities in chickens. However, the immune enhancing mechanisms of probiotics in the chicken have not been studied in depth. More importantly, a very limited number of probiotic products are currently available with proven immune enhancing capabilities in chickens. Therefore, the proposed studies are aimed to screen commensal lactobacilli present in the chicken gut microbiota to identify isolates that have superior immunomodulatory activities. Furthermore, we intend to assess the efficacy of these bacteria either alone or in combination in reducing colonization of the chicken gut by Salmonella.