An Abundance of Escherichia coli Is Harbored by the Mucosa- Associated Bacterial Flora of Interleukin-2-Deficient Mice

Abstract

Mice deficient in interleukin-2 are well suited for use as an animal model for inflammatory bowel disease. Raised under specific-pathogen-free conditions, interleukin-2-deficient mice develop an inflammatory bowel disease resembling ulcerative colitis in humans. The finding that colitis was attenuated when the mice were kept under germfree conditions implies that the resident intestinal flora is involved in the pathogenesis of colitis. The present study addresses the composition of the mucosa-associated bacterial flora in colon samples from interleukin-2-deficient mice that developed colitis. This was investigated by comparative 16S ribosomal DNA (rDNA) sequence analysis and fluorescence in situ hybridization using rRNA-targeted fluorescent probes to quantify the bacterial populations of the mucosa-associated flora. The investigations revealed distinct differences in the bacterial composition of the mucosa-associated flora between interleukin-2-deficient mice and healthy controls. Fluorescence in situ hybridization identified up to 10% of the mucosa-associated flora in interleukin-2-deficient mice as Escherichia coli, whereas no E. coli was detected in the mucosa from healthy wild-type mice. This finding was consistent with the results from comparative 16S rDNA analysis. About one-third of the clones analyzed from 16S rDNA libraries of interleukin-2-deficient mice represented Enterobacteriaceae, whereas none of the clones analyzed from the healthy controls harbored 16S rDNA from Enterobacteriaceae. The abundance of E. coli in the colonic mucosa of interleukin-2-deficient mice strongly suggests a participation in the pathogenesis of colitis in the interleukin-2-deficient mouse model for inflammatory bowel disease.Ulcerative colitis and Crohn's disease are chronic diseases of the intestinal tract which are characterized by a strong activation of the intestinal mucosa-associated immune system due to a complex interaction of genetic, immunologic, and environmental factors. Despite numerous investigations over the last half-century, the etiology of inflammatory bowel diseases (IBD) remains unknown (32). Today several animal models for IBD are established and allow the investigation of factors which are involved in the pathogenesis of the disease (6). Interleukin-2 (IL-2)-deficient mice represent an animal model in which mice develop a colitis resembling ulcerative colitis in humans (4). Colitis developed spontaneously when the mice were kept under specific-pathogen-free (SPF) housing conditions but was greatly attenuated when they were raised under germfree conditions (29). This finding is consistent in various rodent models of IBD and demonstrates the pivotal role that the endogenous intestinal bacterial flora plays in the initiation and perpetuation of the chronic inflammation (23, 27, 36) Results from studies of T-cell-receptor-deficient mice and of rats with induced experimental colitis indicate that the species composition of the microbial flora, rather than the intestinal flora per se, seems to be of particular...

Gram-Negative Bacteria Aggravate Murine Small Intestinal Th1-Type Immunopathology following Oral Infection with Toxoplasma gondii

“…These findings are well in line with the amelioration of ileitis developing in SAMP1/ YitFc mice by antibiotic treatment (29 -31, 60) and the abundance of E. coli and Bacteroides/Prevotella spp. detected in experimental colitis (61,62) and in patients with IBD (13). Furthermore, the colitogenic potential of both bacterial groups was determined earlier (18,19,21,63) and the contributions of Gram-negative bacteria to the severity of intestinal inflammation were supported by successful antibiotic treatment of experimental colitis and in human IBD (22,64,65), as well as in GvHD (8).…”

Short-term modifications in the distal gut microbiota of weaning mice induced by a high-fat diet

“…Phylogenetic identification based on comparative analysis of partial 16S rRNA gene sequences may have been hampered by the short sequences obtained from excised and re-amplified DGGE bands. Notably, the sequence from the Bacteroides-Prevotella group showed a perfect match to an uncultured bacterial clone sequence representative of the mucosa-associated community of mouse colon (Schuppler et al, 2004), and the sequence from the Blautia coccoides/E. rectale group was related most closely to a recently submitted uncultured mouse clone sequence from a 16S rRNA gene library of mouse caecum microbiota (Wen et al, 2008).…”

Absence of Microbiota (Germ-Free Conditions) Accelerates the Atherosclerosis in ApoE-Deficient Mice Fed Standard Low Cholesterol Diet

“…We used oligonucleotide probes for 16S rRNA, universal probe EUB 338 (5´-GCTGCCTCCCG-TAGGAGT-3´) FITC − , which detects all bacteria 13) , Bac 303 (5´-CCAATGTGGGGGACCTT-3´) FITC − for detection of Bacteroides spp. and Prevotella 14) , ECO 1531 (5´-CACCGTAGTGCCTCGTCA-3´) CY 3 − Escherichia coli 15) , E rectale 482 (5´-GCTTCTTAGT-CARGTACCG-3´) FITC − for detection of Eubacterium rectale and Clostridium coccoides 16) , and SFB 1008 (5´-GCGAGCTTCCCTCATTACAAGG-3´)FITC − for SFB 17) . All samples were counterstained using 4, 6-diamidino-2-phenylindole (DAPI; Sigma-Aldrich, St. Louis, USA).…”