Abstract
Actinomycosis is a form of painful abscess in the gastrointestinal tract or in deep tissue caused by actinomyces species. They are one of the commensal bacteria in the oral cavity and gastrointestinal tract of humans but can opportunistically cause infection in immunosuppressive hosts through invasion of breached mucosa or necrotic tissue while mimicking malignancy, gastrointestinal tuberculosis, and inflammatory bowel disease. Actinomyces israelii is, by far, the major and most common human pathogen throughout literatures. By virtue of rarity and diagnostic confusion with masquerading malignancies, only 10% of the cases have been diagnosed preoperatively, so as to be able to verge patients from undergoing unnecessary surgical intervention. Herein, we present a rare case of complicated diverticular abscess manifested by Actinomyces meyeri after postoperative tissue diagnosis.