Adherent-invasive Escherichia coli associated with granulomatous colitis and extraintestinal dissemination in a Sphynx cat

Abstract

This case report describes a case of granulomatous colitis (GC) associated with adherent-invasive Escherichia coli (AIEC) with extension to cecum and ileum and dissemination to multiple lymph nodes, the spleen, and brain in a 10-year-old, male Sphynx cat. The cat had an episode of diarrhea 4 months prior to consultation due to sudden blindness. Signs rapidly progressed to ataxia, seizures, and death. Gross and histologic findings were consistent with granulomatous inflammation in all affected organs. In situ hybridization confirmed the presence of intracellular E. coli within enterocytes and infiltrating macrophages, and whole genome sequencing identified virulence traits commonly linked to AIEC strain. This is the first characterization of GC in a cat associated to AIEC resembling the metastatic form of Crohn's disease in humans and GC of dogs. Extraintestinal involvement might provide evidence of the ability of AIEC to promote granulomatous inflammation beyond the gut.

Keywords: AIEC; adherent-invasive Escherichia coli; cat; extraintestinal dissemination; granulomatous colitis.

Figure 1.

Granulomatous colitis associated with adherent-invasive Escherichia coli, colon, cat. (a) The mucosa and submucosa are markedly thickened by white tan and firm coalescing nodules. The overlying mucosa is ulcerated. (b) Section of the ileocolic junction showing mucosal necrosis (asterisk) and inflammation dissecting the lamina propria and extending deep into the submucosa. Inset: Inflammatory infiltrate consisting predominantly of foamy and epithelioid macrophages; small numbers of multinucleated giant cells; and few neutrophils, lymphocytes, and plasma cells. Hematoxylin and eosin (HE). (c) Numerous rod-shaped bacteria are identified within the cytoplasm of 2 macrophages with Warthin Starry stain. (d) E. coli 16S rRNA probe hybridization (red) is present throughout the necrotic mucosa (asterisk), crypt lumen, and affected lamina propria and submucosa. (e) Probe hybridization (red) is prominent within the cytoplasm of enterocytes, and (f) intracellularly within macrophages (arrow). In situ hybridization (ISH), B-E.Coli-16SrRNA probe. AIEC, adherent-invasive Escherichia coli.