Direct Streptococcus pneumoniae real-time PCR serotyping from pediatric parapneumonic effusions

To determine the serotypes of Streptococcus pneumoniae responsible for pneumonia complicated by parapneumonic effusion in children, we performed real-time PCR based pneumococcal "serotyping" directly on parapneumonic fluid samples.

Specimens were collected at two children's hospitals in Ontario, Canada from 2009 to 2011. Samples in which S. pneumoniae was detected by PCR were tested with serotype-specific 5'exonuclease PCR assays for the 13 serotypes contained in the 13-serotype pneumococcal vaccine.

Thirty-five S. pneumoniae PCR-positive pleural samples were studied. Pneumococcal serotyping PCR assays were positive for 34 of 35 (97%). Serotype 3 was detected most frequently, in 19/35 (54%), followed by serotype 19A in 9/35 (26%), serotype 7 F/A in 4/35 (11%), serotype 1 in 1/35 (3%), and serotype 6A also in 1/35 (3%).

PCR testing demonstrated that the vast majority (97%) of S. pneumoniae parapneumonic effusions were caused by serotypes present in the 13-serotype vaccine that were not present in the original 7 serotype vaccine. This suggests that use of the 13-serotype vaccine could potentially prevent many S. pneumoniae pneumonias complicated by parapneumonic effusion in our region, provided serotype replacement does not occur.