Urinary pneumococcal serotype detection among children with and without community-acquired pneumonia

Urinary antigen detection (UAD) assays can address diagnostic challenges with culture-based identification of S. pneumoniae. We aimed to evaluate the utility of Pfizer's UAD1 and UAD2 assays for pneumococcal serotype surveillance in children with community acquired pneumonia (CAP) or upper respiratory tract infections (URI).

From March 2021-December 2023, children 3 months to 5 years who presented to the Children's Hospital Colorado Emergency Department with respiratory symptoms were enrolled as CAP or URI; healthy children served as controls. Nasal swabs were tested for pneumococcus by PCR. UAD assays identified pneumococcal serotypes from urine. Groups were compared using descriptive statistics.

We enrolled 407 controls, 202 with URI, and 280 with CAP. Positivity thresholds were set for all UAD serotypes. Pneumococcal nasal swab positivity was 23% for CAP, 17% for URI, and 3% in controls. Serotypes 3, 15B/C, 19 F, and 35B were frequent in nasal swabs in children with CAP or URI. UAD identified serotypes in 13% with CAP and 5% with URI. The most common urine serotypes were 19 F, 22 F, and 9 N. Among children with a nasal swab collected, 28/190 (15%) with CAP and 4/135 (3%) with URI had a positive UAD; 7 (3.7%) and 2 (1.5%), respectively, were the same serotype identified by nasal swab.

UAD may be useful in differentiating pneumococcal serotypes in children with CAP and URI from controls. For most, serotypes identified in nasal swabs were not those identified by UAD suggesting UAD positivity was not due to pneumococcal carriage. The Pfizer UAD assay could be utilized for population monitoring of serotype distribution among children with CAP.