Prevalence data of Streptococcus pneumoniae serotypes in pleural infections may be underestimated when surveillance is only based in culture and conventional phenotypic serotyping techniques, impairing follow up of vaccines performance.

This underestimation, particularly of serotype 3, was revealed by the Laboratorio Regional de Salud Pública de la Comunidad de Madrid (Spain) when they used S. Pneumostrip, a technique based on PCR + hybridization, to serotype 30 culture-negative pleural fluid specimens from paediatric Invasive Pneumococcal Disease patients, obtained between September 2018 and December 2022.

The results obtained with S. PneumoStrip showed that the number of serotype 3 cases detected was significantly higher than the rest of the serotypes: 21 samples of the 30 analyzed. The serotypes found in the other samples were 8, 19A, 1, 10A, 9A/9V and 33F/33A. Among those twenty-one children infected by serotype 3, 18 had received at least one dose of PCV13, and among them, sixteen children received three or four doses, indicating a failure in vaccine coverage.

Those results are quite important, because reference serotyping techniques, as Quellung test, need living bacteria to be performed, and in those negative-culture samples a serotype result cannot be obtained, leading to incomplete vaccine performance follow up data.

For this reason, the routine implementation of PCR procedures as S. Pneumostrip technique in order to identify the serotype involved in culture-negative specimens provides additional information and can improve substantially the microbiological investigation of Streptococcus pneumoniae pleural infections. This approach can support epidemiological surveillance and monitoring of immunization plans.

The study has been presented in a Scientific Letter in the Journal of Infectious Diseases and Clinical Microbiology, which can be accessed from the following link:

In addition, this extended study with other sample types will be presented in a poster at the ECCMID 2023 congress to be held next week in Copenhagen:

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