Novel Invasive E. coli Found in Crohn's Disease

While intestinal bacteria have been implicated as a pivotal factor in the development of Crohn's disease, the specific components of the complex polymicrobial enteric environment driving the inflammatory response have not been resolved.

In a recent publication investigators at Cornell University (Ithaca, NY, USA) used a combination of culture-independent analysis of bacterial diversity (16S rDNA library analysis, quantitative polymerase chain reaction [PCR], and fluorescence in situ hybridization) and molecular characterization of cultured bacteria to examine the ileal mucosa-associated flora of patients with Crohn's disease involving the ileum, Crohn's disease restricted to the colon, and healthy individuals.

The investigators reported in the July 12, 2007, online edition of The ISME Journal: Multidisciplinary Journal of Microbial Ecology that the number of E. coli in situ correlated with the severity of ileal disease and that invasive E. coli were restricted to inflamed mucosa. E. coli strains isolated from the ileum were predominantly novel in phylogeny, displayed pathogen-like behavior in vitro, and harbored chromosomal and episomal elements similar to those described in extraintestinal pathogenic E. coli and pathogenic Enterobacteriaceae.

"Given that only about 20% of fecal bacteria can be cultured, our group adopted a broad culture-independent approach to target specific subgroups of bacteria for quantitative in situ analysis and culture based characterization,” said Dr. Kenneth Simpson, professor of small animal medicine at Cornell University. "Our findings raise the possibility that a novel group of E. coli contains opportunistic pathogens that may be causally related to chronic intestinal inflammation in susceptible individuals. They suggest that an integrated approach that considers an individual's mucosa-associated flora in addition to disease phenotype and genotype may improve outcome.”


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