Actinomyces meyeri Causing Cerebral Abscess in a Patient on Methotrexate: A Rare Case Report and Systematic Review of the Literature.

Central nervous system (CNS) actinomycosis is a rare, serious, life-threatening, suppurative infection caused by Actinomyces species. Actinomyces are anaerobic Gram-positive bacteria, which can be normally isolated from the polymicrobial flora of the gastrointestinal- and genital tracts. They are considered very low virulent bacteria to humans. However, they can lead to several types of local or disseminated infections, if certain pathologic states or immunodeficiency occur. Intracranial abscesses caused by Actinomyces meyeri are rarely reported in adults. In this case report, we describe a 66-year-old woman who presented to the emergency department due to progressive complaints of altered sensorium and low-grade fever, due to an A. meyeri-related brain abscess. The only risk factor was represented by immunodeficiency due to the therapy with Methotrexate and steroids.