Specific Bacterial Species May Initiate Crohn’s Disease

Patients newly diagnosed with pediatric Crohn's disease (CD) had significantly different levels of certain types of bacteria in their intestinal tracts.

One group of bacteria, known as Proteobacteria, was present at higher levels in mild cases, as compared with moderate to severe disease, and age-matched controls.

Scientists at the University of New South Wales (Sydney, Australia) examined the microbial flora of fecal samples from 19 children newly diagnosed with CD and 21 age-matched controls were analyzed using high-throughput sequencing to determine differences in the microbial composition between CD patients and controls.

Analysis of the microbial composition of specific bacterial groups revealed that Firmicutes percentages were significantly lower in CD patients than in controls and that this was due largely to changes in the class Clostridia. The percentages of Bacteroidetes and Proteobacteria were higher and significantly higher in CD patients than in controls, respectively. Both the detection frequencies of Bacteroidetes and Firmicutes correlated positively and negatively, respectively, with the calculated pediatric Crohn's disease activity index scores of patients.

The scientists grew Campylobacter concisus from biopsy specimens from children with CD and examined their ability to attach and invade intestinal cells, as compared with strains grown from patients with gastroenteritis, and healthy controls. That investigation showed that only specific C. concisus strains could invade intestinal cells, that these strains were associated with Crohn's, and that they carried a plasmid which was absent from noninvasive C. concisus strains.

Hazel M. Mitchell, PhD, the principle investigator on the study, said, “We deliberately chose to examine children newly diagnosed with Crohn's Disease, as we thought this would increase our chances of detecting species that may be involved in initiating Crohn's disease. Our finding is consistent with recent studies showing that members of the Proteobacteria, including Escherichia coli and C. concisus may play a role in initiating Crohn's disease.” The study was published in the October 2012 edition of the Journal of Clinical Microbiology.

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University of New South Wales