Pulmonary Pneumatocele in a Pneumonia Patient Infected with Extended-Spectrum β-Lactamase Producing Proteus mirabilis

Abstract

Pulmonary pneumatoceles are air-filled thin-walled spaces within the lung and are rare in adult cases of pneumonia. We report the case of a 74-year-old male who was admitted with a cough and sputum production. He had been treated with oral dexamethasone since a brain tumorectomy 6 months prior. Contrast-enhanced computed tomography (CT) of the chest revealed a large pneumatocele in the right middle lobe and peripheral pneumonic consolidation. Bronchoalveolar lavage was performed; cultures identified extended-spectrum β-lactamase (ESBL) producing Proteus mirabilis. A 4-week course of intravenous ertapenem was administered, and the pneumatocele with pneumonia resolved on follow-up chest CT. To the best of our knowledge, this is the first reported case of pulmonary pneumatocele caused by ESBL-producing P. mirabilis associated with pneumonia.

Keywords: Beta-Lactamase; Pneumonia; Proteus mirabilis.

Figure 1. Initial chest radiograph and chest computed tomography. (A) Chest radiograph showing cystic lesion in the medial aspect of right lower lung zone. (B-D) Contrast-enhanced computed tomography showing an approximately 5.6×2.5-cm region of peripheral consolidation, with a central emphysematous change lesion in the right middle lobe, abutting to right minor fissure.

Figure 2. Chest radiograph and chest computed tomography findings after treatment. (A) Chest radiograph taken 2 months after commencement of antibiotic treatment showing resolution of the cystic lesion in the right lower lung zone. (B, C) Contrast-enhanced computed tomography taken 2 months after commencement of antibiotic treatment showing improvement of the lesion in the right middle lobe.