Bacteroides vulgatus protects against Escherichia coli-induced colitis in gnotobiotic interleukin-2-deficient mice.
OBJECTIVE
The microflora plays a crucial role in inflammatory bowel diseases (IBDs). Specific pathogen-free (SPF), but not germ-free, interleukin (IL)-2-deficient (IL-2-/-) mice develop colitis. The colitogenicity of commensal bacteria was determined.


METHODS
Gnotobiotic IL-2-/- and IL-2+/+ mice were colonized with Escherichia coli mpk, Bacteroides vulgatus mpk, or both bacterial strains, or with E. coli strain Nissle 1917. DNA arrays were used to characterize E. coli mpk. Colitis was analyzed by histology and real-time reverse-transcription polymerase chain reaction (RT-PCR) for interferon (IFN)-gamma, tumor necrosis factor (TNF)-alpha, IL-10, and CD14 messenger RNA (mRNA) expression. Bacterial numbers in feces and bacterial localization in the colon was determined by culture and fluorescence in situ hybridization (FISH).


RESULTS
IL-2-/- but not IL-2+/+ mice monocolonized with E. coli mpk developed colitis, whereas mono-association with B. vulgatus mpk, or E. coli Nissle, or co-colonization with E. coli mpk and B. vulgatus mpk, did not induce colitis. DNA array experiments and cellular studies revealed that E. coli mpk is a nonpathogenic strain. FISH and culture methods revealed that the anticolitogenic effect of B. vulgatus mpk on E. coli mpk cannot be explained by a significant reduction in numbers of E. coli in the colon. E. coli mpk-induced colitis was associated with increased IFN-gamma, TNF-alpha, CD14, and IL-10 mRNA expression in the colon.


CONCLUSIONS
In IL-2-/- mice, B. vulgatus mpk protects against E. coli mpk-triggered colitis by an unknown mechanism. E. coli Nissle does not induce colitis. Various bacterial species common to the microflora differ in their ability to trigger IBD.
Waidmann
Marc
M
Institut für Medizinische Mikrobiologie und Krankenhaushygiene, Eberhard Karls-Universität, Tübingen, Germany.
Bechtold
Oliver
O
Frick
Julia-Stefanie
JS
Lehr
Hans-Anton
HA
Schubert
Sören
S
Dobrindt
Ulrich
U
Loeffler
Jürgen
J
Bohn
Erwin
E
Autenrieth
Ingo B
IB
D000818:Animals; D001439:Bacteroides / Q000254:growth & development*; D003092:Colitis / Q000382:microbiology* / Q000503:physiopathology / Q000517:prevention & control; D004926:Escherichia coli / Q000254:growth & development*; D004927:Escherichia coli Infections / Q000382:microbiology* / Q000503:physiopathology / Q000517:prevention & control; D005243:Feces / Q000382:microbiology; D005260:Female; D015870:Gene Expression; D005856:Germ-Free Life; D007376:Interleukin-2 / Q000235:genetics*; D007422:Intestines / Q000382:microbiology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D013047:Specific Pathogen-Free Organisms
D007376:Interleukin-2