Heiko C. Rath

Genetic and environmental factors are important in the pathogenesis of clinical and experimental chronic intestinal inflammation. We investigated the influence of normal luminal bacteria and several groups of selected bacterial strains on spontaneous gastrointestinal and systemic inflammation in HLA-B27 transgenic rats. Rats maintained germfree for 3-9 mo were compared with littermates conventionalized with specific pathogen-free bacteria. Subsequently, germfree transgenic rats were colonized with groups of five to eight bacteria that were either facultative or strictly anaerobic. Transgenic germfree rats had no gastroduodenitis, colitis, or arthritis, but developed epididymitis and dermatitis to the same degree as conventionalized rats. Colonic proinflammatory cytokine expression was increased in transgenic conventionalized rats but was undetectable in germfree and nontransgenic rats. Colitis progressively increased over the first 4 wk of bacterial exposure, then plateaued. Only transgenic rats colonized with defined bacterial cocktails which contained Bacteroides spp. had colitis and gastritis. Normal luminal bacteria predictably and uniformly induce chronic colonic, gastric and systemic inflammation in B27 transgenic F344 rats, but all bacterial species do not have equal activities.

BACKGROUND: Experimental studies have shown that luminal antigens are involved in chronic intestinal inflammatory disorders such as Crohn's disease and ulcerative colitis. Alteration of the intestinal microflora by antibiotic or probiotic therapy may induce and maintain remission. The aim of this randomized, placebo-controlled trial was to determine the effect of oral Lactobacillus GG (L. GG) to induce or maintain medically induced remission. METHODS: Eleven patients with moderate to active Crohn's disease were enrolled in this trial to receive either L. GG (2 x 10(9) CFU/day) or placebo for six months. All patients were started on a tapering steroid regime and received antibiotics for the week before the probiotic/placebo medication was initiated. The primary end point was sustained remission, defined as freedom from relapse at the 6 months follow-up visit. Relapse was defined as an increase in CDAI of >100 points. RESULTS: 5/11 patients finished the study, with 2 patients in each group in sustained remission. The median time to relapse was 16 +/- 4 weeks in the L. GG group and 12 +/- 4.3 weeks in the placebo group (p = 0.5). CONCLUSION: In this study we could not demonstrate a benefit of L. GG in inducing or maintaining medically induced remission in CD.

Resident bacteria are incriminated in the pathogenesis of experimental colitis and inflammatory bowel diseases. We investigated the relative roles of various enteric bacteria populations in the induction and perpetuation of experimental colitis. HLA-B27 transgenic rats received antibiotics (ciprofloxacin, metronidazole, or vancomycin-imipenem) in drinking water or water alone in either prevention or treatment protocols. Mice were treated similarly with metronidazole or vancomycin-imipenem before or after receiving 5% dextran sodium sulfate (DSS). Germfree transgenic rats were colonized with specific-pathogen-free enteric bacteria grown overnight either in anaerobic or aerobic atmospheres. Nontransgenic rats colonized with anaerobic bacteria served as negative controls. Although preventive metronidazole significantly attenuated colitis in transgenic rats and DSS-treated mice, it had no therapeutic benefit once colitis was established. Ciprofloxacin also partially prevented but did not treat colitis in B27 transgenic rats. In both animal models vancomycin-imipenem most effectively prevented and treated colitis. Germfree transgenic rats reconstituted with enteric bacteria grown under anaerobic conditions had more aggressive colitis than those associated with aerobic bacteria. These results suggest that a subset of resident luminal bacteria induces colitis, but that a complex interaction of commensal aerobic and anaerobic bacteria provides the constant antigenic drive for chronic immune-mediated colonic inflammation.

Resident bacteria play an important role in initiating and perpetuating gastrointestinal inflammation. We previously demonstrated that six commensal bacteria including Bacteroides vulgatus caused more aggressive colitis and gastritis in HLA-B27 transgenic rats than did the other five bacteria without B. vulgatus. This study compared the degree of gastrointestinal inflammation in gnotobiotic HLA-B27 transgenic rats monoassociated with either B. vulgatus or Escherichia coli. Gnotobiotic transgenic rats raised in Trexler isolators were selectively colonized with either B. vulgatus or E. coli. Control rats were either germfree or colonized with six common commensal bacteria (Streptococcus faecium, E. coli, Streptococcus avium, Eubacterium contortum, Peptostreptococcus productus, and B. vulgatus [DESEP-B]). After 1 month, all the rats were killed and tissues were prepared for histologic and biochemical evaluation. Colitis induced by B. vulgatus monoassociation was almost equal to that in DESEP-B-colonized rats and was significantly more severe than E. coli-induced colitis, which was absent by histological testing and mild by colonic myeloperoxidase and interleukin-1beta concentration determinations. However, gastritis was detectable only in DESEP-B-associated rats. These studies suggest that not all resident bacteria have equal proinflammatory capabilities, since B. vulgatus alone is more active than E. coli alone in inducing colitis, and that colitis and gastritis result from different luminal bacterial stimuli.