A case report: colonic and urethral infectious granuloma associated with fungal pathogen and extended-spectrum beta-lactamases-producing Escherichia coli in a Thai Bangkeaw dog

A 4-year-old, neutered male Thai Bangkeaw dog presented with clinical signs of diarrhea, pollakiuria and a mass -like lesion between the bulbus glandis and testicular sac 2 weeks after castration. Ultrasound (U/S) revealed a mass-like lesion from the urethra expanded to the colon. A computerized tomography (CT) scan indicated that the mass had invaded the colon and nearby lymph node. Bacterial culture from the lesion identified infection caused by extended -spectrum beta-lactamases-producing Escherichia coli (ESBL-producing E. coli). Using fine needle aspiration (FNA) of the mass-like lesion, cytology showed irregular, negatively stained hyphal structures. Given the very large size of the lesion, surgical excision could not be performed. A combination of itraconazole, terbinafine and carprofen was prescribed for medical treatment. Additionally, amikacin was given following antimicrobial susceptibility testing. However, there was no improvement after medical treatment. Ultimately, euthanasia was selected. The gross findings revealed an area of swelling primarily located at the caudoventral abdomen due to marked edema and hemorrhage with a focal tract lesion from the focus of the hair skin defect through the urethra. Regionally, the descending colon was markedly thickened. Microscopically, the intestinal wall was obliterated by nodular and coalescing aggregates of granulomas surrounding many indiscernible hyphae with non-parallel walls, non-dichotomous branching and rare septations. Organisms were negatively stained with Periodic Acid Schiff (PAS) but strongly highlighted by Grocott's methenamine silver (GMS) staining. The findings were consistent with intestinal pythiosis. However, macerate tissue culture for fungi and oomycetes was negative.