Brevundimonas diminuta-Induced Lung Abscess in an Immunocompetent Adult: A Rare Case Report

Lung abscesses caused by Brevundimonas diminuta (B. diminuta) are a rare occurrence, particularly in immunocompetent adults. We present the case of a 47-year-old male with a history of COPD, bipolar disorder, and seizure disorder, who presented with a productive cough, worsening shortness of breath, yellow sputum, weight loss, and fatigue over a period of three weeks. Clinical examination revealed decreased breath sounds in the left upper lung zones. Laboratory investigations showed an elevated white cell count, while blood cultures identified B. diminuta. Imaging with computed tomography (CT) confirmed the presence of a 4.2x2.0 cm cavitary lesion consistent with a lung abscess. The patient was successfully treated with a combination of Ampicillin/Sulbactam and Azithromycin, followed by a course of oral Augmentin. Given the size of the abscess and favorable response to antibiotic therapy, invasive procedures were deemed unnecessary. This case underscores the importance of considering unusual pathogens in the etiology of lung abscesses, even in immunocompetent individuals, and highlights the successful management with appropriate antibiotic therapy.