B73-05 Persistent Pneumonia With a Twist: Recognizing Pulmonary Actinomycosis

Abstract Introduction Pulmonary actinomycosis is a rare, chronic infection caused by Actinomyces species—anaerobic, Gram-positive filamentous bacteria that normally colonize the oropharynx. Thoracic involvement represents 15-20% of actinomycosis cases and is often related to aspiration or chronic airway disease. Clinical manifestations such as cough, fever, and weight loss are nonspecific, while imaging often mimics malignancy, tuberculosis, or fungal disease. Because of its indolent course and poor culture yield, diagnosis is frequently delayed. Histopathologic confirmation of filamentous bacterial colonies remains the gold standard. We present a case of pulmonary actinomycosis initially misdiagnosed as recurrent community-acquired pneumonia, emphasizing early bronchoscopy and evidence-based oral therapy. Case Presentation A 70-year-old woman with asthma, rheumatoid arthritis, hypothyroidism, hypertension, dyslipidemia, atrial fibrillation, gastroesophageal reflux disease, and recurrent otitis presented with persistent cough and malaise unresponsive to outpatient antibiotics. Despite normal pulmonary function tests, she required two hospitalizations for worsening dyspnea and fever. Chest CT revealed diffuse patchy consolidations evolving into bilateral ground-glass and reticulonodular opacities, raising concern for malignancy or atypical infection. Laboratory studies showed leukocytosis and mild hyponatremia.After multiple antibiotic failures, bronchoscopy with bronchoalveolar lavage demonstrated filamentous, branching Gram-positive bacteria consistent with Actinomyces. Stains for mycobacteria and fungi were negative. The patient began oral amoxicillin 500 mg three times daily for six months. She showed rapid clinical improvement, with near-complete radiologic resolution at three months and full recovery by the end of therapy. At follow-up, she remained asymptomatic without recurrence. Discussion Pulmonary actinomycosis is a diagnostic chameleon that mimics chronic pneumonia and malignancy. Delays arise from nonspecific symptoms, low organism recovery, and overlapping imaging patterns. This case highlights the importance of early bronchoscopic sampling in non-resolving pneumonia and of maintaining suspicion for actinomycosis in patients with aspiration risk factors such as gastroesophageal reflux and chronic airway disease. Although traditional therapy involves prolonged intravenous penicillin followed by oral therapy, growing evidence supports exclusive oral regimens in stable patients. Our patient’s complete recovery with oral therapy alone reinforces this practical, resource-efficient strategy.ConclusionActinomycosis should remain on the differential for persistent pulmonary infiltrates unresponsive to standard antibiotics. Early bronchoscopy expedites diagnosis, and prolonged oral antibiotic therapy can achieve complete recovery, avoiding unnecessary invasive workup or hospitalization. This abstract is funded by: none