Bilateral Breast Involvement by Actinomyces neuii in an Immunocompetent Male Patient: An Exceptional Case.

Actinomyces neuii is a gram-positive, non-branching, rod-shaped bacterium that rarely causes infection in humans. To our knowledge, we report the first case of primary bilateral breast actinomycosis caused by A. neuii in an immunocompetent male patient. A 40-year-old man presented with chronic bilateral green nipple discharge. Despite a prior left breast abscess drainage and six weeks of oral penicillin V, symptoms persisted. Culture of the nipple discharge identified A. neuii. The patient's history included nipple piercings, and a mammogram confirmed the abscess. After failure of penicillin V, he was switched to oral linezolid, which led to resolution of the discharge, though induration remained on follow-up. Recognizing atypical actinomycosis, thorough evaluation, and microbiological confirmation are key to effective treatment and better patient outcomes.