The significance of upper airway density of Streptococcus pneumoniae and respiratory viruses in the aetiology and severity of paediatric community-acquired pneumonia in Norway: An observational study.

Objectives: Diagnosing paediatric Community-Acquired Pneumonia (CAP) is challenging due to the difficulty in obtaining lung specimens. Studies suggest that the upper-airway density of Streptococcus pneumoniae is related to the risk and severity of CAP. We studied the association between S. pneumoniae and its density in the upper airways with CAP and its severity. Additionally, we examined the relationship between respiratory viral load and severe CAP.

Methods: Seven hundred fifteen children with radiologically confirmed CAP and 673 controls were enrolled over 11 years. Nasopharyngeal aspirates (NPA) were tested for 20 viruses and bacteria using semi-quantitative polymerase chain reaction (PCR). NPAs positive for S. pneumoniae were further analysed by quantitative PCR. Adjusted odds ratios (aORs) and 95 % confidence intervals (CIs) were calculated to assess the association between S. pneumoniae density and CAP and CAP severity.

Results: Fewer cases than controls were colonised with S. pneumoniae (culture: 37.6 % vs 51.9 %, p < .001; PCR: 55.3 % vs 69.1 %, p < .001), and the median density was lower (6.20 log¹⁰ copies/mL vs 6.62 log¹⁰ copies/mL, p < .001). No association was found between S. pneumoniae density and CAP severity. CAP severity was significantly associated with high Respiratory Syncytial Virus (RSV) load (aOR 2.26, 95 % CI 1.43-3.57, p < .001) or high Human Metapneumovirus (HMPV) load (aOR 4.32, 95 % CI 2.19-8.48, p < .001), adjusted by pneumococcal density, other pathogens, age, sex, comorbidities, prior antibiotics and season.

Conclusions: Detection and density of S. pneumoniae in the upper airways do not correlate with CAP presence or severity. High RSV and HMPV loads were linked to severe CAP.