Parapneumonic Empyema Complicating Community-acquired Pneumonia: Etiology in the Era of Pneumococcal Vaccination and Role of Molecular Diagnosis.

BACKGROUND

Impact of pneumococcal conjugate vaccines (PCVs) on pneumococcal disease is well described; pneumococcus is infrequently identified by culture in pneumonia. Yield is higher when pleural fluid is cultured. Polymerase chain reaction (PCR) in pleural fluid samples improves pathogen identification, particularly in the case of S. pneumoniae.

METHODS

Healthy children with empyema who underwent pleural fluid drainage were eligible. Demographics and PCV immunization status were collected. Blood/pleural fluid cultures were obtained. Pleural fluid samples were sent for PCR for pathogen. Serotyping was done by Neufeld-Quellung reaction on pneumococcus isolates, and PCR in culture negative cases.

RESULTS

From December 2018 to September 2023, 74 patients were enrolled. Pathogens were cultured in 22 patients (29.7%), with pneumococcus found in 6 (27.3%). PCR identified additional pathogens in 23 patients (31.1%), including 18 pneumococci (81.8%) and real-time PCR identified 5 more pneumococci, totaling 29 pneumococci, with 23 (79.3%) detected by PCR only. Serotype information was available for 27 (93.1%) pneumococci; 22 (81.5%) were identified as PCV-13 serotypes, with serotype 3 being present in 17 (63%) cases. Among patients with a PCV-13 serotype detected through culture or molecular methods, 15 (68.2%) were fully vaccinated with PCV-13, including 11 of 17 (65%) with serotype 3.

CONCLUSION

S. pneumoniae , particularly serotype 3, is the leading bacterial pathogen in children ≤18 years old. Molecular diagnosis enhances pathogen detection. Ongoing surveillance is crucial to monitor etiology changes as new pneumococcal vaccines are introduced.