The aggregation of entero-hemorrhagic Escherichia coli with Lactobacillus strains The relationship with their probiotic activities

「Introduction」 As highlighted by the outbreak in Sakai, Japan, in 1996 2,14) entero-hemorrhagic Escherichia coli (EHEC) infection endangers a wide range of communities through causing a serious complication, hemolytic uremic syndrome7), especially in juvenile and senile patients. One crucial risk factor of EHEC infection is that the minimally required bacterial numbers to initiate the systemic infection is very small. Thus, various approaches to prevent the disease at the front line have been considered. Among them, an application of probiotic bacteria could be a practical candidate, because of the relative safety and the convenience. Several studies with Lactobacillus and Bifidobacterium reported their effectiveness in vivo and in vitro1,5,9,10). In our in vitro infection model of EHEC, the internalization to a human colon epithelial cell line was suppressed by viable L. rhamnosus but not by L. plantarum, L. gaserri or L. casei. In contrast, the adhesion and colonization of EHEC were not suppressed at all, suggesting that this effect was not a simple competition on the cell surface6). During the course of infection, the growth rate of EHEC and the viability of host cells were not affected by any of Lactobacillus strains tested.