High-resolution CT findings of culture-confirmed enterococcal pneumonia: A two-center retrospective study

This study aimed to describe the high-resolution computed tomography (HRCT) features of culture-confirmed hospital-acquired pneumonia caused by Enterococcus, an uncommon infection rarely characterized radiologically.

We retrospectively reviewed HRCT scans of adults with microbiologically proven enterococcal pneumonia at two tertiary centers between 2019 and 2024. Patients with other pathogens, pulmonary malignancy, pulmonary edema or hemorrhage, or poor-quality images were excluded. Two thoracic radiologists independently evaluated predefined CT features, with consensus reached in cases of discrepancy. Interobserver agreement was measured using Cohen's kappa (κ).

Among 105 patients screened, 20 met the inclusion criteria (12 males, 8 females; mean age 62.9 years). The most common CT findings were groundglass opacities and pleural effusions (each in 70%), followed by consolidation (60%), bronchial wall thickening (60%), and intralobular reticulations (50%). Centrilobular nodules were identified in 45%, interlobular septal thickening in 40%, bronchiectasis in 30%, mediastinal lymphadenopathy in 20%, and empyema in 5%. Abnormalities were usually bilateral with lower-lobe predominance, and mixed features were often observed within the same lobe. On follow-up, 10 (50%) patients improved radiographically, whereas 10 (50%) showed disease progression and died despite treatment. Interobserver agreement was high, ranging from κ= 0.68 to κ= 1.00, indicating substantial to almost perfect concordance across features.

Enterococcal pneumonia occurs mainly in older, comorbid, and critically ill patients and is associated with high mortality. HRCT commonly demonstrates ground-glass opacities, consolidation, and pleural effusions. Although pleural effusion appeared more frequent than in other bacterial pneumonias, the imaging findings overall were nonspecific, and microbiological confirmation remains essential for diagnosis.