Parapneumonic effusions related to Streptococcus pneumoniae: serotype and disease severity trends from 2006 to 2018 in Bristol, UK

Abstract

Rationale: Streptococcus pneumoniae epidemiology is changing in response to vaccination and some data suggest that empyema incidence is increasing. However, differences exist between the UK and US studies. We describe trends in the clinical phenotype of adult pneumococcal pleural infection, including simple parapneumonic effusions (SPE) in the pneumococcal conjugate vaccination (PCV) era.

Objectives: To determine whether there were differences in pneumococcal disease presentation and severity associated with pleural infection.

Methods: A retrospective cohort study, all adults ≥16 years admitted to three large UK hospitals, 2006-2018 with pneumococcal disease. 2477 invasive pneumococcal cases were identified: 459 SPE and 100 pleural infection cases. Medical records were reviewed for each clinical episode. Serotype data were obtained from the UK Health Security Agency national reference laboratory.

Results: Incidence increased over time, including non-PCV-serotype disease. PCV7-serotype disease declined following paediatric PCV7 introduction, but the effect of PCV13 was less apparent as disease caused by the additional six serotypes plateaued with serotypes 1 and 3 causing such parapneumonic effusions from 2011 onwards.Patients with pleural infection had a median survival 468 days (95% CI 340 to 590) vs 286 days (95% CI 274 to 335) in those with SPE. Pleural infection associated with frank pus had lower 90-day mortality than pleural infection without pus (0% vs 29%, p<0.0001). 90-day mortality could be predicted by baseline increased RAPID (Renal, Age, Purulence, Infection source, and Dietary factors) score (HR 15.01, 95% CI 1.24 to 40.06, p=0.049).

Conclusions: Pneumococcal infection continues to cause severe disease despite the introduction of PCVs. The predominance of serotype 1 and 3 in this adult UK cohort is in keeping with previous studies in paediatric and non-UK studies. Rising non-PCV serotype disease and limited impact of PCV13 on cases caused by serotypes 1 and 3 offset the reductions in adult pneumococcal parapneumonic effusion disease burden observed following the introduction of the childhood PCV7 programme.

Keywords: bacterial infection; empyema; pleural disease; respiratory infection.

Figure 1

Vaccine group serotype trends in pneumococcal parapneumonic effusions in Bristol, UK 2006–2018. (A) Incidence of pneumococcal parapneumonic effusion (per 100 000 adults), calculated using adult population data from the Office of National Statistics (online supplemental data 5). (B) Proportion of serotyped disease caused by vaccine serotype group as shown from 2006 to 2018. Dashed lines show the introduction of paediatric PCV7 and PCV13. (C) Proportion of serotyped disease caused by the major individual serotypes from 2006 to 2018. The black line shows the trend in proportion of disease, with the grey area representing the 95% CI. NVT, non-vaccine type; PCV, polysaccharide conjugate vaccine.

Figure 2

One-year survival in patients with pneumococcal parapneumonic effusions. (A) Kaplan-Meier survival curve and number at risk for patients with simple parapneumonic effusion (SPE) (red line) and pleural infection (blue line). (B) Kaplan-Meier survival curve and number at risk for patients with pneumococcal pleural infection for low (red line), medium (blue line) ad high (black line) RAPID score groups. The number of subjects at risk immediately before each time point is listed in a numbers-at-risk table. RAPID, Renal, Age, Purulence, Infection source, and Dietary factors.