Parapneumonic effusion in italian children: diagnosis and serotyping by real-time polymerase chain reaction

The aim of this study was to achieve diagnosis and serotyping of empyema cases using real-time polymerase chain reaction directly on pleural fluid in a large cohort of Italian children hospitalized with CAP complicated by empyema in pre- and post-pneumococcal conjugate vaccine (PCV13) era. One hundred and thirty five children 0-16 years admitted with a diagnosis of parapneumonic effusion (PPE) to 24 Pediatric Hospitals all over Italy were included in the study. Realtime PCR was performed in all 135 patients and was positive for at least one of the tested pathogens in 109/135 (80.7%) patients. Streptococcus pneumoniae was the most frequent and was found in 84/109 (77.1%) samples. In non-pneumococcal PPE pathogen more frequently found were Streptococcus pyogenes (8/135 cases) in younger (mean age 3.89 years) and Fusobacterium necrophorum or nucleatum (5/135 cases) in adolescents (mean age 11.49 years). Between 2007 and 2010 (before the inclusion of Prevenar 13 in the Italian schedule) we found 81 cases of PPE. Streptococcus pneumoniae was found in 45/81 (55.6%). Betweeen 2011 and January 2014 we found where 55 cases of PPE. Streptococcus pneumoniae was the most frequent and was found in 39/55 (70.1%). We have shown that in Italy there was not an increase in the incidence of other pathogens in PPE after the introduction of Prevenar13. RT-PCR allowed serotyping in 81/84 (96.4%) patients with pneumococcal PPE. Actually, serotype distribution in PPE demonstrated a large preponderance of serotypes 1, 3 and 19A (non-PCV7 serotypes). Serotype 1 appeared significantly associated with complications and older age. Since the mean age for PPE is usually older than 3 years, at this point of time the direct effect of PCV13 vaccination in reducing PPE incidence is not yet evident . However in the 3 years since PCV13 has been introduced in Italy we did not found pneumococcal PPE in children aged <3,5 years. No cases in children aged <2 years, no cases in vaccinated children. In 47 patients both cultures of pleural fluid and RT-PCR were performed at the same time. In the subgroup of 34 patients in which both tests were performed and etiologic diagnosis was obtained, the diagnosis was obtained by RT-PCR only in 30/34 (88.2%) patients, by both tests in 4/34 (11.8%) and by culture only in none. Realtime PCR appears 8.5 times more sensitive in individuating an etiologic agent in PPE and is significantly more sensitive than culture in achieving etiologic diagnosis of PPE.