Adherent and InvasiveEscherichia coliIs Associated with Granulomatous Colitis in Boxer Dogs

Abstract

The mucosa-associated microflora is increasingly considered to play a pivotal role in the pathogenesis of inflammatory bowel disease. This study explored the possibility that an abnormal mucosal flora is involved in the etiopathogenesis of granulomatous colitis of Boxer dogs (GCB). Colonic biopsy samples from affected dogs (n ‫؍‬ 13) and controls (n ‫؍‬ 38) were examined by fluorescent in situ hybridization (FISH) with a eubacterial 16S rRNA probe. Culture, 16S ribosomal DNA sequencing, and histochemistry were used to guide subsequent FISH. GCB-associated Escherichia coli isolates were evaluated for their ability to invade and persist in cultured epithelial cells and macrophages as well as for serotype, phylogenetic group, genome size, overall genotype, and presence of virulence genes. Intramucosal gram-negative coccobacilli were present in 100% of GCB samples but not controls. Invasive bacteria hybridized with FISH probes to E. coli. Three of four GCB-associated E. coli isolates adhered to, invaded, and replicated within cultured epithelial cells. Invasion triggered a "splash"-type response, was decreased by cytochalasin D, genistein, colchicine, and wortmannin, and paralleled the behavior of the Crohn's disease-associated strain E. coli LF 82. GCB E. coli and LF 82 were diverse in serotype and overall genotype but similar in phylogeny (B2 and D), in virulence gene profiles (fyuA, irp1, irp2, chuA, fepC, ibeA, kpsMII, iss), in having a larger genome size than commensal E. coli, and in the presence of novel multilocus sequence types. We conclude that GCB is associated with selective intramucosal colonization by E. coli. E. coli strains associated with GCB and Crohn's disease have an adherent and invasive phenotype and novel multilocus sequence types and resemble E. coli associated with extraintestinal disease in phylogeny and virulence gene profile.

Gastrointestinal microorganisms in cats and dogs: a brief review

“…However, this is often challenging due to high similarities in the 16S rRNA gene composition among phylogenetically related microorganisms. FISH can also provide important information about the morphology and spatial distribution of microorganisms in the GI tract (Simpson et al 2006).…”

Microflora in Crohn’s disease: the emergence of adherent and invasiveEscherichia coli

“…16S rDNA libraries generated from GCB dogs are dominated by sequences for Enterobacteriaceae, predominantly E. coli and Shigella and FISH probes recognize invasive E. coli within the colonic mucosa (in the lamina propria and macrophages) of Boxer dogs with GCB but not unaffected controls, and non-GCB colitis. E. coli strains isolated from affected Boxer dogs display an AIEC pathotype in cultured cells, and resemble LF82 in phylogeny and virulence genes [45]. Subsequent studies of GCB-affected dogs have shown that antibiotic-induced clinical remission correlates with eradication of invasive E. coli.…”

“…In contrast to pathogenic E. coli, such as O157:H7, AIEC strains differ in serotype, overall genotype [26,45] and ribotype [50] and are not a single virulent clone. By use of PCR-based virulence screening and genome subtraction, we discovered that AIEC strains with unique multilocus sequence type sequences and distinct phylogenetic backgrounds (A, B1, B2 and D) harbor chromosomal and episomal elements that are homologous to those described in extraintestinal pathogenic E. coli (uropathogenic E. coli [UPEC] and avian pathogenic E. coli), and pathogenic Enterobacteriaceae, such as Salmonella and Yersinia [26,45], and support the possibility that AIEC strains share common pathoadaptive determinants of virulence.…”

“…In contrast to pathogenic E. coli, such as O157:H7, AIEC strains differ in serotype, overall genotype [26,45] and ribotype [50] and are not a single virulent clone. By use of PCR-based virulence screening and genome subtraction, we discovered that AIEC strains with unique multilocus sequence type sequences and distinct phylogenetic backgrounds (A, B1, B2 and D) harbor chromosomal and episomal elements that are homologous to those described in extraintestinal pathogenic E. coli (uropathogenic E. coli [UPEC] and avian pathogenic E. coli), and pathogenic Enterobacteriaceae, such as Salmonella and Yersinia [26,45], and support the possibility that AIEC strains share common pathoadaptive determinants of virulence. For example, nucleotide sequences resembling ratA in Salmonella typhimurium, which is associated with colonization of the cecum and Peyer's patches [51], and another resembling a hemolysin coregulated protein (hcp) secreted by a type VI secretion system associated with virulence in Vibrio [52], are potentially disease-relevant genes present in AIEC from CD and GCB.…”

“…Granulomatous colitis of Boxer dogs (GCB) is a severe disease of unknown etiology that typically affects Boxer dogs [45]. GCB has features in common with UC (macroscopic appearance, regional distribution and immunopathology), Whipple's disease (PAS-positive macrophages) and CD (granulomatous inflammation, bacteria within macrophages and may respond to fluroquinolones) in humans but it is not identical to any of these disease syndromes [46][47][48][49].…”