title: Antimicrobial Activity of Lactobacillus spp. Isolated From Fecal Flora of Healthy Breast-Fed Infants Against Diarrheagenic Escherichia coli.
abstract: BACKGROUND
  Among the enteric pathogens, diarrheagenic Escherichia coli are important causes of diarrhea in children in both developing and industrialized countries. Some Lactobacillus species are commonly used as probiotics, with effects especially against acute diarrhea in childhood.
  
  
  OBJECTIVE
  The aim of this study was to explore antimicrobial activity of Lactobacillus strains isolated from fecal flora of healthy breast-fed infants against five diarrheagenic E. coli pathotypes such as enteroaggregative E. coli (EAEC), enterohaemorrhagic E. coli (EHEC) enteroinvasive E. coli (EIEC), enteropathogenic E. coli (EPEC) and enterotoxigenic E. coli (ETEC).
  
  
  METHODS
  Fecal samples were collected from seven healthy breast-fed infants between 1 to 18 months of age in Tehran city, Iran. Identification of Lactobacillus isolates was performed by biochemical and 16S rRNA gene sequencing methods. An agar well diffusion assay was used for detection of antimicrobial activity of Lactobacillus isolates against five diarrheagenic E. coli pathotypes.
  
  
  RESULTS
  A total of 20 Lactobacillus isolates were identified from stool samples. Lactobacillus fermentum was the most frequently isolated strain, followed by L. plantarum and L. rhamnosus. Seven Lactobacillus strains including L. fermentum (four isolates), L. paracasei (one isolate), L. plantarum (one isolate) and L. rhamnosus (one isolate) had a mild inhibitory activity against diarrheagenic E. coli. The mechanism of inhibitory activity of Lactobacillus strains appeared to be due to the production of organic acids or hydrogen peroxide.
  
  
  CONCLUSIONS
  Our findings show that Lactobacillus strains with human origin had a mild inhibitory activity against the diarrheagenic E. coli, and these strains may be useful as probiotic candidates in prevention of intestinal infections caused by diarrheagenic E. coli.
authors: Department of Pathobiology, School of Public Health, Tehran University of Medical Sciences, Tehran, IR Iran.
authors: Abolfazl
authors: A
authors: Davoodabadi
authors: Department of Pathobiology, School of Public Health, Tehran University of Medical Sciences, Tehran, IR Iran; Food Microbiology Research Center, Tehran University of Medical Sciences, Tehran, IR Iran.
authors: Mohammad Mehdi
authors: MM
authors: Soltan Dallal
authors: Food Microbiology Research Center, Tehran University of Medical Sciences, Tehran, IR Iran.
authors: Elahe
authors: E
authors: Lashani
authors: Department of Biology, Faculty of Science, Central Tehran Branch, Islamic Azad University, Tehran, IR Iran.
authors: Maryam
authors: M
authors: Tajabadi Ebrahimi
keywords: Escherichia coli; Infant; Lactobacillus; inhibition