Escherichia coli-associated granulomatous diseases in three cats.

Granulomatous diseases associated with Escherichia coli infection are uncommon in domestic animals. In cats, malakoplakia and granulomatous ulcerative colitis are the only described forms. We investigated the clinical and pathological findings of E. coli-associated granulomatous diseases in three cats. In all cases the affected organs were infiltrated by many macrophages containing periodic acid-Schiff-positive intracytoplasmic granules. The macrophages immunolabelled for ionized calcium-binding adapter molecule 1 and E. coli. The first case involved the urinary bladder and was diagnosed as malakoplakia. The second case had small intestinal granulomatous enteritis and lymphadenitis of the mesenteric, celiac, colonic, mandibular and mediastinal lymph nodes. The third case had granulomatous enteritis, splenitis and lymphadenitis of the mesenteric, iliac, aortic, renal, hypogastric and sacral lymph nodes. Peyer's patches were predominantly affected in the small intestines of both the second and third cases. Although malakoplakia has been documented previously, the findings in the second and third cases suggest novel forms of granulomatous disease associated with E. coli in cats, with notable primary involvement of lymphoid tissue.