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

乳酸菌是一组可以在哺乳动物和鸟类肠道中发现的微生物。包括乳酸菌在内的几种乳酸菌已被发现具有益生菌活性。一些乳酸菌是肠道微生物群落的正常成员，对宿主的健康有益。这些健康益处包括控制致病肠道微生物和增强宿主免疫反应，包括全身和局部肠道。在家禽业中，一些做法，如预防性使用抗生素，改变了肠道微生物群落的组成，并可能限制共生微生物控制沙门氏菌等致病微生物的能力。事实上，禽类产品是人类食源性疾病的主要来源。在加拿大，沙门氏菌在2004年引起了大约5200例食源性疾病的报告病例，2001-02年每例报告病例的平均估计费用为1,100美元。还应指出，根据一些估计，未报告的沙门氏菌病病例数是报告病例数的10倍。因此，家禽业迫切需要制定控制食源性病原体从家禽向人类传播的战略。含有乳酸菌的益生菌提供了一种这样的策略。除了益生菌对肠道病原菌的控制作用外，乳酸菌还具有鸡的免疫调节作用。然而，益生菌对鸡的免疫增强机制尚未深入研究。更重要的是，目前只有非常有限的益生菌产品被证明具有增强鸡免疫力的能力。因此，本研究旨在筛选鸡肠道菌群中存在的共生乳酸菌，以鉴定具有优越免疫调节活性的分离菌。此外，我们打算评估这些细菌单独或联合减少沙门氏菌在鸡肠道定植的功效。

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.