Strain competition restricts colonization of an enteric pathogen and prevents colitis

EMBO Rep. 2016 Sep;17(9):1281-91. doi: 10.15252/embr.201642282. Epub 2016 Jul 18.

Abstract

The microbiota is a major source of protection against intestinal pathogens; however, the specific bacteria and underlying mechanisms involved are not well understood. As a model of this interaction, we sought to determine whether colonization of the murine host with symbiotic non-toxigenic Bacteroides fragilis could limit acquisition of pathogenic enterotoxigenic B. fragilis We observed strain-specific competition with toxigenic B. fragilis, dependent upon type VI secretion, identifying an effector-immunity pair that confers pathogen exclusion. Resistance against host acquisition of a second non-toxigenic strain was also uncovered, revealing a broader function of type VI secretion systems in determining microbiota composition. The competitive exclusion of enterotoxigenic B. fragilis by a non-toxigenic strain limited toxin exposure and protected the host against intestinal inflammatory disease. Our studies demonstrate a novel role of type VI secretion systems in colonization resistance against a pathogen. This understanding of bacterial competition may be utilized to define a molecularly targeted probiotic strategy.

Keywords: colonization resistance; enterotoxigenic Bacteroides fragilis; in vivo strain competition; probiotics; type VI secretion.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antibiosis
  • Bacteroides fragilis / classification
  • Bacteroides fragilis / genetics
  • Colitis / chemically induced
  • Colitis / microbiology*
  • Colitis / pathology
  • Colitis / prevention & control
  • Disease Models, Animal
  • Host-Pathogen Interactions*
  • Immunity
  • Intestinal Mucosa / microbiology*
  • Intestinal Mucosa / pathology
  • Mice
  • Microbial Interactions*