Pleural Empyema Due to Gemella morbillorum: A Rare Etiology in a High-risk Patient.

Pleural empyema is a severe complication of pneumonia, tipically caused by Streptococcus pneumoniae or Staphylococcus aureus. We present a rare case of empyema due to Gemella morbillorum, an orophrarynx commensal. Risk factors include alcoholism, immunocompromised state, and poor oral hygiene. Its slow growth and resemblance to Streptococcus viridans complicate diagnosis, often requiring Matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry for accurate identification. While beta-lactams (penicilins and most cephalosporins) remain first-line therapy, our case highlights successful treatment in a penicillin-allergic patient using vancomycin and clindamycin, providing an alternative regimen. Other options, including macrolides, fluoroquinolones and tetracyclines, may be considered based on antimicrobial susceptibility testing. Optimal management combines pleural drainage and prolonged antibiotic therapy (≥4 weeks).