Vibrio cholerae interactions with the gastrointestinal tract: lessons from animal studies.

Vibrio cholerae is a curved Gram-negative rod that causes the diarrheal disease cholera. One hundred and twenty five years of study of V. cholerae microbiology have made this lethal pathogen arguably the most well-understood non-invasive mucosal pathogen. Over the past 25 years, modern molecular techniques have permitted the identification of many genes and cellular processes that are critical for V. cholerae colonization of the gastrointestinal tract. Review of the literature reveals that there are two classes of genes that influence V. cholerae colonization of the suckling mouse intestine, the most commonly used animal model to study V. cholerae pathogenesis. Inactivation of one class of genes results in profound attenuation of V. cholerae intestinal colonization, whereas inactivation of the other class of genes results in only moderate colonization defects. The latter class of genes suggests that V. cholerae may colonize several intestinal niches that impose distinct requirements and biological challenges, thus raising the possibility that there is physiologic heterogeneity among the infecting population. Efficient V. cholerae intestinal colonization and subsequent dissemination to the environment appears to require temporally ordered expression of sets of genes during the course of infection. Key challenges for future investigations of V. cholerae pathogenicity will be to assess the degree of heterogeneity in the infecting population, whether such heterogeneity has functional significance, and if stochastic processes contribute to generation of heterogeneity in vivo.