title: Gram-negative bacteria aggravate murine small intestinal Th1-type immunopathology following oral infection with Toxoplasma gondii.
abstract: Oral infection of susceptible mice with Toxoplasma gondii results in Th1-type immunopathology in the ileum. We investigated gut flora changes during ileitis and determined contributions of gut bacteria to intestinal inflammation. Analysis of the intestinal microflora revealed that ileitis was accompanied by increasing bacterial load, decreasing species diversity, and bacterial translocation. Gram-negative bacteria identified as Escherichia coli and Bacteroides/Prevotella spp. accumulated in inflamed ileum at high concentrations. Prophylactic or therapeutic administration of ciprofloxacin and/or metronidazole ameliorated ileal immunopathology and reduced intestinal NO and IFN-gamma levels. Most strikingly, gnotobiotic mice in which cultivable gut bacteria were removed by quintuple antibiotic treatment did not develop ileitis after Toxoplasma gondii infection. A reduction in total numbers of lymphocytes was observed in the lamina propria of specific pathogen-free (SPF), but not gnotobiotic, mice upon development of ileitis. Relative numbers of CD4(+) T cells did not differ in naive vs infected gnotobiotic or SPF mice, but infected SPF mice showed a significant increase in the frequencies of activated CD4(+) T cells compared with gnotobiotic mice. Furthermore, recolonization with total gut flora, E. coli, or Bacteroides/Prevotella spp., but not Lactobacillus johnsonii, induced immunopathology in gnotobiotic mice. Animals recolonized with E. coli and/or total gut flora, but not L. johnsonii, showed elevated ileal NO and/or IFN-gamma levels. In conclusion, Gram-negative bacteria, i.e., E. coli, aggravate pathogen-induced intestinal Th1-type immunopathology. Thus, pathogen-induced acute ileitis may prove useful to study bacteria-host interactions in small intestinal inflammation and to test novel therapies based on modulation of gut flora.
authors.affiliation: Institut für Mikrobiologie und Hygiene, Charité-Universitätsmedizin Berlin, Campus Benjamin Franklin and Campus Mitte, Hindenburgdamm 27, D-12203 Berlin, Germany.
authors.forename: Markus M
authors.initials: MM
authors.lastname: Heimesaat
authors.forename: Stefan
authors.initials: S
authors.lastname: Bereswill
authors.forename: André
authors.initials: A
authors.lastname: Fischer
authors.forename: David
authors.initials: D
authors.lastname: Fuchs
authors.forename: Daniela
authors.initials: D
authors.lastname: Struck
authors.forename: Julia
authors.initials: J
authors.lastname: Niebergall
authors.forename: Hannah-Katharina
authors.initials: HK
authors.lastname: Jahn
authors.forename: Ildikò R
authors.initials: IR
authors.lastname: Dunay
authors.forename: Annette
authors.initials: A
authors.lastname: Moter
authors.forename: Dorothee M
authors.initials: DM
authors.lastname: Gescher
authors.forename: Ralf R
authors.initials: RR
authors.lastname: Schumann
authors.forename: Ulf B
authors.initials: UB
authors.lastname: Göbel
authors.forename: Oliver
authors.initials: O
authors.lastname: Liesenfeld
mesh_terms: D000818:Animals; D004926:Escherichia coli; D006090:Gram-Negative Bacteria / Q000472:pathogenicity*; D007082:Ileum / Q000382:microbiology / Q000473:pathology; D007249:Inflammation / Q000382:microbiology; D007371:Interferon-gamma / Q000032:analysis; D007421:Intestine, Small / Q000382:microbiology* / Q000469:parasitology / Q000473:pathology*; D051379:Mice; D008810:Mice, Inbred C57BL; D009569:Nitric Oxide / Q000032:analysis; D018720:Prevotella; D018417:Th1 Cells / Q000382:microbiology / Q000473:pathology*; D014122:Toxoplasma / Q000382:microbiology; D014123:Toxoplasmosis / Q000150:complications
chemical_list: D009569:Nitric Oxide; D007371:Interferon-gamma