Clinical characteristics of community-acquired primary pleural infection compared to postpneumonic pleural infection:...

Data on the clinical features and treatment outcomes in patients with primary pleural infection (PI) are limited. This study aimed to investigate the clinical characteristics of these patients.

In this retrospective study, patients with community-acquired PI, diagnosed based on pleural fluid analysis, were classified into postpneumonic and primary PI groups according to computed tomography (CT) findings. Clinical variables, microbiological data, and CT findings were compared between the two groups.

Approximately 28 % of patients with community-acquired PI presented as primary PI. Treatment success rates and in-hospital or 30-day mortality were comparable between the two groups. However, compared to the postpneumonic PI group, the primary PI group was significantly younger and had lower proportions of patients with Pneumonia Severity Index classes 4-5 and RAPID (Renal, Age, Purulence, Infection source, and Dietary factors) score >3. On CT scans, subpleural abscesses were present in less than half of the patients in the primary PI group, compared to most patients in the postpneumonic PI group. Pleural enhancement and extrapleural fat proliferation were more frequently observed in patients with primary PI than in those with postpneumonic PI. In the primary PI group, Streptococcus anginosus group was the most common pathogen, accounting for nearly half of the causative organisms.

Patients with primary PI had similar treatment outcomes compared to those with postpneumonic PI. However, different causative pathogens and radiologic findings of primary PI suggest a distinct pathogenesis of PI independent of pneumonia.