Immune protection mediated by the probiotic Lactobacillus rhamnosus HN001 (DR20) against Escherichia coli O157:H7 infection in mice.

This study investigated the protective effects of feeding the immunoenhancing probiotic Lactobacillus rhamnosus HN001 against Escherichia coli O157:H7 infection in murine (BALB/c and C57BL/6 mice) challenge infection models. Mice were fed milk-based diets supplemented with L. rhamnosus HN001 (3 x 10(8) cfu g(-1)) for 7 days prior to and following oral challenge with E. coli O157:H7. Morbidity and feed intake were measured for 1 week following challenge; pathogen translocation to spleen, liver and blood, and humoral and cellular immunological responses (specific antibody and phagocytosis) were measured in a sub-sample of ostensibly healthy animals 1 week post-challenge. Results showed that, after challenge, L. rhamnosus HN001-fed mice exhibited lower cumulative morbidity and bacterial translocation rates, compared to non-probiotic-fed control mice. Significantly higher intestinal anti-E. coli IgA responses and blood leucocyte phagocytic activity were recorded among probiotic-fed mice compared to controls. These results demonstrate that feeding the probiotic L. rhamnosus HN001 to mice can reduce the severity of E. coli O157:H7 infection, and suggest that this reduction may be associated with enhanced humoral and cellular immune responses. Copyright 2002 Federation of European Microbiological Societies