Christel Neut

Presence of adherent Escherichia coli strains in ileal mucosa of patients with Crohn's disease

BACKGROUND & AIMS Infectious agents are suspected of being involved in the pathogenesis of Crohns disease. This study was designed to look for the presence of virulent Escherichia coli strains associated with the ileal mucosa of patients with Crohns disease. METHODS E. coli strains were recovered from resected chronic ileal lesions (n = 20), neoterminal ileum after surgery from patients with (n = 19) and without (n = 11) endoscopic recurrence, and controls (n = 13). Bacterial adhesion was determined in vitro using intestinal cell lines; other associated virulence factors were assessed by DNA hybridization and polymerase chain reaction experiments. RESULTS None of the strains harbored any of the virulence factor-encoding genes of E. coli involved in acute enteric diseases. However, mannose-resistant adhesion to differentiated Caco-2 cells was found for 84.6% and 78.9% of the E. coli strains isolated from chronic and early recurrent lesions, respectively, compared with 33% of controls (P < 0.02). In addition, 21.8% of the strains induced a cytolytic effect by synthesis of an alpha-hemolysin. CONCLUSIONS E. coli strains isolated from the ileal mucosa of patients with Crohns disease adhere to differentiated intestinal cells and may disrupt the intestinal barrier by synthesizing an alpha-hemolysin.

Lactobacillus acidophilus modulates intestinal pain and induces opioid and cannabinoid receptors

Abdominal pain is common in the general population and, in patients with irritable bowel syndrome, is attributed to visceral hypersensitivity. We found that oral administration of specific Lactobacillus strains induced the expression of μ-opioid and cannabinoid receptors in intestinal epithelial cells, and mediated analgesic functions in the gut—similar to the effects of morphine. These results suggest that the microbiology of the intestinal tract influences our visceral perception, and suggest new approaches for the treament of abdominal pain and irritable bowel syndrome.

Dysbiosis in inflammatory bowel disease

Abundant data have incriminated intestinal bacteria in the initiation and amplification stages of inflammatory bowel diseases. However, the precise role of intestinal bacteria remains elusive. One theory has suggested a breakdown in the balance between putative species of “protective” versus “harmful” intestinal bacteria—this concept has been termed “dysbiosis”. Arguments in support of this concept are discussed.

Changes in the bacterial flora of the neoterminal ileum after ileocolonic resection for Crohn’s disease

OBJECTIVE:Bacterial agents have been implicated in the early recurrence of Crohns disease after ileocolectomy. The aim of our study was to identify and quantify bacteria associated with the ileal mucosa in patients and controls and to correlate specific bacteria with recurrence.METHODS:The predominant bacterial microflora of the ileum were enumerated and identified, aerobically and anaerobically, in biopsies obtained at the time of surgery or by endoscopy from 61 patients with Crohns disease and 10 ileocolectomy controls. The 61 specimens were comprised of 13 ileal biopsies taken from resection specimens, seven taken after ileostomy, and 41 taken after ileocolectomy.RESULTS:Ileocolectomy induced a significant increase in bacterial counts and variety in the neoterminal ileum in both patients and controls that was not observed in ileostomy biopsies. Comparison between patients and controls revealed greater numbers of Escherichia coli and enterococci in Crohns disease and of bifidobacteria and ruminococci in controls. Early recurrence was associated with high counts of E. coli and bacteroides and the frequent isolation of fusobacteria.CONCLUSION:After ileocolectomy, colonization of the neoterminal ileum is increased. Our data suggest that increases in the populations of specific bacteria such as E. coli, enterococci, bacteroides, and fusobacteria may be important in postoperative recurrence of Crohns disease.

Crohn disease–associated adherent-invasive E. coli bacteria target mouse and human Peyer’s patches via long polar fimbriae

Crohn disease (CD) is a multifactorial disease in which an abnormal immune response in the gastrointestinal (GI) tract leads to chronic inflammation. The small intestine, particularly the ileum, of patients with CD is colonized by adherent-invasive E. coli (AIEC)--a pathogenic group of E. coli able to adhere to and invade intestinal epithelial cells. As the earliest inflammatory lesions are microscopic erosions of the epithelium lining the Peyers patches (PPs), we investigated the ability of AIEC bacteria to interact with PPs and the virulence factors involved. We found that AIEC bacteria could interact with mouse and human PPs via long polar fimbriae (LPF). An LPF-negative AIEC mutant was highly impaired in its ability to interact with mouse and human PPs and to translocate across monolayers of M cells, specialized epithelial cells at the surface of PPs. The prevalence of AIEC strains harboring the lpf operon was markedly higher in CD patients compared with controls. In addition, increased numbers of AIEC, but not LPF-deficient AIEC, bacteria were found interacting with PPs from Nod2(-/-) mice compared with WT mice. In conclusion, we have identified LPF as a key factor for AIEC to target PPs. This could be the missing link between AIEC colonization and the presence of early lesions in the PPs of CD patients.

Mesenteric fat in Crohn’s disease: a pathogenetic hallmark or an innocent bystander?

In the first half of the 20th century, white adipose tissue (WAT) was mainly viewed as an isolated tissue protecting the organism from heat loss and a passive energy storage compartment. Similarly to other species such as Drososophila melanogaster , it is now well recognised that mammalian fat tissue is not solely a reservoir for excess nutrients but also an active and dynamic organ involved in the development of metabolic syndromes and the regulation of immunity and inflammation. The older anatomical literature repeatedly mentions a close association between adipose tissue and lymphoid organs in various mammals including humans, suggesting a potential role of WAT in the host immune response. Several recent studies indicate that adipocytes could function as macrophage-like cells1 as they express receptors related to the innate immune system and secrete major mediators of inflammation, such as tumour necrosis factor alpha (TNFα). Consistent with this hypothesis,2 the biology of adipocytes is particularly implicated in chronic diseases, such as obesity3 and atherosclerosis.4 This review will focus on the normal and pathophysiological functions of mesenteric WAT (mWAT), which may play an important role in the inflammatory and fibrotic processes in Crohn’s disease, a frequent and complex form of inflammatory bowel disease (IBD). Long considered as the “anatomists’ Cinderella”,5 mWAT is now recognised as a multifunctional organ. Notably located around organs such as the gut or the lungs, adipocytes may have evolved strategies to drive immune responses to microbial invaders by expressing different innate immune sensors. In addition its function as a storage organ, WAT plays a major endocrine and immune role by expressing several hormones and various mediators (fig 1). To clarify the nomenclature, we will refer to the hormones and immunomodulatory molecules derived from adipocytes as adipormones and adipocytokines, respectively. Figure 1  Adipormones, adipocytokines and their receptors. …

Mesenteric fat as a source of C reactive protein and as a target for bacterial translocation in Crohn's disease

Objective Mesenteric fat hyperplasia is a hallmark of Crohns disease (CD), and C reactive protein (CRP) is correlated with disease activity. The authors investigated whether mesenteric adipocytes may be a source of CRP in CD and whether inflammatory and bacterial triggers may stimulate its production by adipocytes. Design CRP expression in the mesenteric and subcutaneous fats of patients with CD and the correlation between CRP plasma concentrations and mesenteric messenger RNA (mRNA) levels were assessed. The impact of inflammatory and bacterial challenges on CRP synthesis was tested using an adipocyte cell line. Bacterial translocation to mesenteric fat was studied in experimental models of colitis and ileitis and in patients with CD. Results CRP expression was increased in the mesenteric fat of patients with CD, with mRNA levels being 80±40 (p<0.05) and 140±65 (p=0.04) times higher than in the mesenteric fat of patients with ulcerative colitis and in the subcutaneous fat of the same CD subjects, respectively, and correlated with plasma levels. Escherichia coli (1230±175-fold, p<0.01), lipopolysaccharide (26±0.5-fold, p<0.01), tumour necrosis factor α (15±0.3-fold, p<0.01) and interleukin-6 (10±0.7-fold, p<0.05) increased CRP mRNA levels in adipocyte 3T3-L1 cells. Bacterial translocation to mesenteric fat occurred in 13% and 27% of healthy and CD subjects, respectively, and was increased in experimental colitis and ileitis. Human mesenteric adipocytes constitutively expressed mRNA for TLR2, TLR4, NOD1 and NOD2. Conclusion Mesenteric fat is an important source of CRP in CD. CRP production by mesenteric adipocytes may be triggered by local inflammation and bacterial translocation to mesenteric fat, providing a mechanism whereby mesenteric fat hyperplasia may contribute to inflammatory response in CD.

Molecular inventory of faecal microflora in patients with Crohn's disease

Intestinal microbial community is involved in the pathogenesis of Crohns disease, but knowledge of its potential abnormalities has been limited by the impossibility to grow many dominant intestinal bacteria. Using sequence analysis of randomly cloned bacterial 16S ribosomal DNA, the dominant faecal species from four Crohns disease patients and four controls were compared. Whereas marked inter-individual differences were observed in the faecal microflora of patients, three remained distantly related to controls on the basis of their operational taxonomic unit composition. Bacteroides vulgatus and closely related organisms represented the only molecular species shared by all patients and exhibited an unusually high rate of occurrence. Escherichia coli clones were isolated only in two patients with ileocolonic Crohns disease. Moreover, numerous clones belonged to phylogenetic groups or species that are commonly not dominant in the faecal microflora of healthy subjects: Pectinatus, Sutterella, Verrucomicrobium, Fusobacterium, Clostridium disporicum, Clostridium glycolicum, Clostridium ramosum, Clostridium innocuum and Clostridium perfringens.

Complete Genome Sequence of Crohn's Disease-Associated Adherent-Invasive E. coli Strain LF82

BACKGROUND Ileal lesions of Crohns disease (CD) patients are abnormally colonized by pathogenic adherent-invasive Escherichia coli (AIEC) able to invade and to replicate within intestinal epithelial cells and macrophages. PRINCIPAL FINDINGS We report here the complete genome sequence of E. coli LF82, the reference strain of adherent-invasive E. coli associated with ileal Crohns disease. The LF82 genome of 4,881,487 bp total size contains a circular chromosome with a size of 4,773,108 bp and a plasmid of 108,379 bp. The analysis of predicted coding sequences (CDSs) within the LF82 flexible genome indicated that this genome is close to the avian pathogenic strain APEC_01, meningitis-associated strain S88 and urinary-isolated strain UTI89 with regards to flexible genome and single nucleotide polymorphisms in various virulence factors. Interestingly, we observed that strains LF82 and UTI89 adhered at a similar level to Intestine-407 cells and that like LF82, APEC_01 and UTI89 were highly invasive. However, A1EC strain LF82 had an intermediate killer phenotype compared to APEC-01 and UTI89 and the LF82 genome does not harbour most of specific virulence genes from ExPEC. LF82 genome has evolved from those of ExPEC B2 strains by the acquisition of Salmonella and Yersinia isolated or clustered genes or CDSs located on pLF82 plasmid and at various loci on the chromosome. CONCLUSION LF82 genome analysis indicated that a number of genes, gene clusters and pathoadaptative mutations which have been acquired may play a role in virulence of AIEC strain LF82.

Phenotypic differentiation of bifidobacteria of human and animal origins

The phenotypes of 153 strains belonging or related to the genus Bifidobacterium were studied. These organisms included 38 collection strains and 115 wild strains (41 strains of human origin, 56 strains of animal origin, and 18 strains obtained from rivers or sewage). Our phenotypic analysis revealed seven main groups that were subdivided into 20 subgroups. Seven subgroups contained no type or collection strain. Among the human strains, the type strains of Bifidobacterium pseudocatenulatum and B. catenulatum fell into group I, which contained the type strains of B. adolescentis (subgroup Ib), B. dentium (subgroup Ic), and B. angulatum (ungrouped). The type strain of B. breve belonged to subgroup IIIa1, and the type strains of B. infantis and B. longum fell into subgroup IIIb1. Group VII comprised only wild strains that were isolated from human infant feces. Among the animal strains, group II consisted mainly of bifidobacteria that were isolated from pig feces and contained the type strains of B. suis (subgroup IIb), B. thermophilum (subgroup IIf), B. choerinum, and B. boum (ungrouped). Wild strains belonging to group V were isolated from pig, calf, cow, and chicken feces; this included the type strains of B. animalis (subgroup Va), B. magnum (subgroup Vb), B. pseudolongum, and B. globosum (subgroup Vc). The strains of human origin (groups I, III, and VII) were well separated from the animal strains (groups II, IV, and V). It was not surprising that the wild strains isolated from surface water or sewage were distributed in the animal groups as well as the human groups. Thus, bifidobacteria can be considered to be successful indicators of human or animal fecal pollution when they are correctly classified. The acidification patterns were not adequate to differentiate Bifidobacterium species, as determined previously by Mitsuoka (Bifidobacteria Microflora 3:11-28, 1984) and Scardovi (p. 1418-1434, in P. H. A. Sneath, N. S. Mair, M. E. Sharpe, and J. G. Holt, ed., Bergeys Manual of Systematic Bacteriology, vol. 2, 1986). However, enzymatic tests furnished new taxonomic criteria for the genus.