Characteristics of patients with serotype 5 pneumococcal pneumonia

Abstract

Despite limited detection in invasive pneumococcal disease (IPD) in the conjugate vaccine era, serotype 5 Streptococcus pneumoniae persists as an important cause of non-invasive pneumococcal pneumonia (NIPP) in adults. Our aim was to describe the characteristics of patients with serotype 5 disease.

A secondary analysis of patients with confirmed pneumococcal pneumonia was conducted from a prospective cohort study of adults hospitalised with community acquired pneumonia between September 2013 and August 2018. Pneumococcal serotypes were identified from urine samples using a multiplex immunoassay (Bioplex24) and from positive blood cultures by phenotypic or genetic serotyping. Patients with serotype 5 were compared to those with non-serotype 5 pneumococcal pneumonia; appropriate summary statistics and univariate odds ratios were calculated.

No difference in age, gender or baseline performance status was observed between serotype 5 (n=60) and non-serotype 5 (n=977) cases. More patients with serotype 5 had chronic lung disease (41.7 vs 27.3%, OR 1.90 95% CI 1.11-3.24) or were immunosuppressed (11.7 vs 4.9%, OR 2.56 95% CI 1.10-5.95). There was no observed difference in disease severity, critical care admission or thirty day mortality between the groups. A higher proportion of serotype 5 cases were vaccinated against seasonal influenza (73.3 vs 53.1%, OR 2.43 95% CI 1.35-4.38) or had received the 23-valent pneumococcal polysaccharide vaccine prior to their index admission (81.7 vs 48.4%, OR 4.75 95% CI 2.42-9.32).

Serotype 5 pneumococcal pneumonia appears more common in patients with chronic lung disease or immunosuppression. A high proportion of patients with serotype 5 were previously vaccinated.