Escherichia coli-induced granulomatous colitis in a cat

Abstract

Case summaryA 10-year-old castrated male domestic shorthair cat presented with a 6 month history of diarrhoea that responded poorly to medical treatment. Ultrasonography revealed moderate thickening of the colonic wall (4.8 mm) and right colic and jejunal lymphadenomegalies. Endoscopic examination revealed partial circumferential narrowing of the transverse colon and friable colonic mucosa with multiple haemorrhagic regions. Histopathological and immunohistochemical examinations revealed a large number of Escherichia coli phagocytosed by periodic acid–Schiff-positive macrophages. Bacterial culture also yielded enrofloxacin-sensitive E coli. The cat was initially treated with prednisolone, which resulted in little improvement. Following histopathological examination and bacterial culture, treatment with enrofloxacin was commenced. Antibacterial therapy resulted in remission of the diarrhoea and an increase in body weight within 14 days.Relevance and novel informationGranulomatous colitis (GC) or histiocytic ulcerative colitis has been rarely described in cats. There has only been one previously published case study involving a cat, and the aetiology remains largely unknown. The current article describes the regression of E coli-related GC following antibacterial treatment in a cat. Clinical signs, histopathological appearance and response to enrofloxacin were similar to those in canine GC. The current findings suggest that E coli also plays an important role in the development of feline GC.

Escherichia coli‐associated granulomatous colitis in a cat

“…In cats, despite no genetic basis for GC to date, this and other case reports demonstrate intracellular E. coli within granulomatous colonic lesions. [9][10][11] This would seem, at least in part, to support E. coli as the causative agent for GC in cats. Studies investigating cats for a potential underlying genetic basis, such as candidate gene NCF2 mutations in humans and dogs, are needed.…”

“…To date, this represents only the fourth reported adult cat with confirmed PAS+ GC. [9][10][11] In this particular case, the presence of severe macrophage infiltration on colonic histopathology prompted concern for an infectious aetiology. Faecal PCR testing and special stains on the biopsies excluded parasitic, fungal, and other noninvasive bacteria as causes for the granulomatous colonic infiltrate.…”

“…8 The decision to treat with a fluoroquinolone was extrapolated from the current recommendations in successfully treated dogs and two prior feline case reports. 5,9,10 One of the limitations in this case was the lack of a bacterial culture for guiding antibiotic selection. In dogs, obtaining this information prior to starting treatment is important because of fluoroquinolone resistance, particularly when administered prior to a definitive diagnosis.…”

“…Like prior cases, this report also confirms both a bacterial aetiology and successful response to antimicrobial treatment for GC in the cat. [9][10][11]…”

“…To date, only three feline cases of GC have been reported, a five‐year‐old Persian, a four‐year‐old domestic shorthair, and a 10‐year‐old domestic shorthair 9–11 . All cases had colonic histopathology lesions identical to that of canine GC and long‐standing remission following the administration of either a fluoroquinolone 9,10 antibiotic or chloramphenicol 11 .…”