Pleural empyema necessitatis caused by Actinomyces meyeri is a rare but severe infection. A. species predominantly A. meyeri and A. israelii represent the second most common pathogen for empyema necessitans after mycobacteria. The incidence is reported in the literature to be 1:300,000. Men are thrice more likely to be affected than women. Pathogenetically, an infection can be triggered by aspiration in immunocompromised individuals which leads to an atelectasis with pneumonitis. In two cases, a 38-year-old construction worker and a 61-year-old woman with ulcerative breast carcinoma, who presented to the local emergency department with a painful swelling of the left chest, diagnostic workup revealed a pleural empyema necessitatis of the left chest. An antibiotic treatment was initiated with piperacillin/tazobactam and sulbactam/ampicillin, respectively. Temporally vacuum-dressing therapy was initiated after surgical debridement. In the course of the procedure, a reconstruction of tissue damage was feasible. The patients were recovered completely and discharged with an oral antibiotic treatment (amoxicillin) for 6 and 12 months, respectively. Thoracic actinomycosis is a relatively uncommon and traditionally chronic, indolent infection secondary to pulmonary infection with A. species . Surgical treatment is generally reserved for cases failing to resolve with antibiotic therapy. Early diagnosis, prompt debridement, and narrow spectrum β-lactam antibiotics can result in complete resolution of infection and good prognosis.
Keywords: Actinomyces meyeri; antibiotic treatment; empyema necessitatis; pleural empyema.