Objective To test the inhabiting effect of Lactobacillus acidophilus on E.coli O157: H7 in intestinal colonization and explore its mechanism. Methods The suppressive effects of Lactobacillus acidophilus against E.coli O157:H7 adhering to Ht29 cells were carried out by competition , exclusion and replacement as-says. Furthermore, we evaluated the cytokine levels of IL-4, IL-12, and INF-γ in serum of mice. In addition, E.coli O157:H7 fecal shedding was monitored and the pathological changes of intestines were observed in mice. Results The competition, exclusion and replacement assays showed Lactobacillus acidophilus inhibited E.coli O157:H7 adhering to Ht29 cells. In vivo, the mice of treatment group were induced significantly higher level of IL-4, IL-12, and INF-γ, though prevention group induced IL-12 only. Fifteen days after E.coli O157:H7 infec-tion, there were 8 mice (80%) in prevention group and 5 mice (50%) in treatment group stopped shedding. Moreover, the pathological changes of intestines of both prevention group and treatment group appeared normal , but control groups showed seriously damaged in intestinal villus. Conclusion Lactobacillus acidophilus inhibits E.coli O157:H7 in intestinal colonization and the preventative effect was better than treatment effect. Thus , Lac-tobacillus acidophilus can be used for E.coli O157:H7 in prevention and treatment infection as probiotics.

OBJECTIVETo investigate the inhibitory effect of Lactobacillus rhamnosus GG ( LGG) against Cronobacter-induced meningitis in neonatal rats.

METHODSThe cell adhesion and invasion capacities of Cronobacter were assayed in Caco-2 cells, and the optimal time length and concentration of the bacterium for infection were determined. The suppressive effects of LGG on the adhesion and invasion of Cronobacter in caco-2 cells were tested by competitive and exclusion experiments, and its inhibitory effect against Cronobacter-induced meningitis was evaluated in neonatal rats.

RESULTSCronobacter showed aggressive adhesion to caco-2 cells with an optimal infection time of 3 h. LGG produced a concentration-dependent inhibition of Cronobacter adhesion and invasion by competing with and excluding the latter for cell adhesion. In neonatal rats, LGG showed an obvious preventive effect and also a moderate therapeutic effect against Cronobacter-induced meningitis.

CONCLUSIONLGG can inhibit Cronobacter entry across the intestinal barrier to achieve preventive and therapeutic effects against Cronobacter-induced meningitis.

Animals ; Animals, Newborn ; Bacterial Adhesion ; Caco-2 Cells ; Cronobacter ; pathogenicity ; Enterobacteriaceae Infections ; therapy ; Humans ; Intestines ; microbiology ; Lactobacillus rhamnosus ; Meningitis, Bacterial ; therapy ; Probiotics ; Rats