Comparison of Effects of Trichuris muris and Spontaneous Colitis on the Proximal Colon Microbiota in C3H/HeJ and C3Bir IL10-/- Mice.

The nematode Trichuris muris has been shown to interact with specific enteric bacteria, but its effects on the composition of its host's microbial community are not fully understood. We hypothesized that Trichuris muris-infected mice would have altered colon microbiota as compared with uninfected mice. Colon histopathology and microbial community structure and composition were examined in mouse models of colitis (C3BirTLR4-/- IL10-/- and C3H/HeJ TLR4-/- IL10+/+ mice) with and without T. muris infection, in uninfected C3BirIL10-/- mice with and without spontaneous colitis, and in normal C3H/ HeJ mice. T. muris-infected mice developed colon lesions that were more severe than those seen in IL10-deficient mice. Ap- proximately 80% of infected IL10-/- mice had colon neutrophilic exudates, and some had extraintestinal worms and bacteria. The composition and structure of proximal colon microbiota were assessed by using terminal restriction fragment length polymorphism analysis targeting the bacterial 16S rRNA gene. Colon microbiota in C3BirIL10-/- and C3H/HeJ mice differed both qualitatively and quantitatively. Trichuris infection significantly altered the relative abundance of individual operational taxonomic units [OTU] but not the composition (presence or absence of OTU) of colon microbiota in the 2 mouse genotypes. When C3BirIL10-/- and C3H/HeJ mouse OTU were considered separately, Trichuris was found to affect the microbiota of C3BirIL10-/- mice but not of C3H/HeJ mice. Even though 34 of the 75 (45%) C3BirIL10-/- mice had spontaneous colitis, neither qualitative nor quantitative differences were detected in microbiota between colitic or noncolitic C3BirIL10-/- mice or noncolitic C3H/HeJ mice. Therefore, Trichuris-infected mice developed distinct microbial communities that were influenced by host background genes; these alterations cannot be attributed solely to colonic inflammation.

Ecological characterization of the colonic microbiota of normal and diarrheic dogs.

We used terminal restriction fragment polymorphism (T-RFLP) analysis to assess (1) stability of the fecal microbiota in dogs living in environments characterized by varying degrees of exposure to factors that might alter the microbiota and (2) changes in the microbiota associated with acute episodes of diarrhea. Results showed that the healthy canine GI tract harbors potential enteric pathogens. Dogs living in an environment providing minimal exposure to factors that might alter the microbiota had similar microbiotas; the microbiotas of dogs kept in more variable environments were more variable. Substantial changes in the microbiota occurred during diarrheic episodes, including increased levels of Clostridium perfringens, Enterococcus faecalis, and Enterococcus faecium. When diet and medications of a dog having a previously stable microbiota were changed repeatedly, the microbiota also changed repeatedly. Temporal trend analysis showed directional changes in the microbiota after perturbation, a return to the starting condition, and then fluctuating changes over time.