Lactobacillus plantarum inhibits the intestinal epithelial migration of neutrophils induced by enteropathogenic Escherichia coli

Background: Lactobacillus plantartum is a Gram-positive bacillus known for its effect as a probiotic agent. The goal of the study was to determine whether L. plantarum is capable of inhibiting the transepithelial neutrophil migration induced by enteropathogenic Escherichia coli (EPEC). Methods: Cultured intestinal epithelial T-84 cell monolayers were rapidly infected with EPEC. L. plantarum or culture supernatants were added to the monolayers before and after the infection. Indium-labeled neutrophils were added to the basolateral side of inverted monolayers. After 150-minute incubation, radioactivity of the neutrophils that migrated in the physiologic direction was assayed, and the number of migrating neutrophils was calculated. L. plantarum was also added to the monolayers before and after EPEC infection, and the number of adherent EPEC was determined by plate counting. Results: EPEC-induced neutrophil migration and EPEC binding to monolayers were inhibited by viable L. plantarum but only when added to the monolayers before EPEC. Culture supernatants failed to inhibit the neutrophil migration. Conclusions: These results suggest that L. plantarum is beneficial in inhibiting neutrophil migration induced by EPEC, but only when preincubated with host epithelia. Rather than an indirect effect through a secreted substance produced by the probiotic agent, its effect is direct and requires the presence of the bacterium. (C) 2003 Lippincott Williams Wilkins, Inc.