1. The Effect of Serotype on Early and Late Mortality in Invasive Pneumococcal Disease in Hull and East Yorkshire
Chloe Walsh
ACF infectious diseases
MSc by thesis (part time)
Supervisors: Dr Gavin Barlow, Dr Victoria Allgar

2. What is Invasive Pneumococcal Disease?
Pneumococcus is a gram positive bacterium that colonises the upper respiratory tract.
Can become pathogenic
Invasive Pneumococcal disease
(IPD) is diagnosed when
Pneumococcus is isolated from
a normally sterile site.

3. Why is IPD important?
Around 2 million deaths are attributed to Pneumococcus globally per annum
Local study of IPD (Elston et al) found that 21.6% of patients died within 30 days of diagnosis
36.8% of patients died within one year of diagnosis.
Overall incidence of IPD of 11.8/ in 2002, increasing to 16.4/ by 2009

4. IPD and Mortality Traditionally considered an acute illness
Both pneumonia and sepsis have been associated with longer term mortality
Determinants of this poorer long term outcome are not fully understood

5. Serotypes Over 90 serotypes based on polysaccharide capsule
“Invasive” versus “colonising”
“Colonising” serotypes associated with poorer outcomes
Capsule is target for vaccination

6. Role of serotype
Meta-analysis has shown 1, 7F and 8 to be associated with better outcomes (“low severity”)
3, 6A, 6B, 9N and 19F are (“high severity”)
Although relationship to acute deaths has been studied, whether serotypes influence longer term mortality has not been established

7. Methods Retrospective cohort
All patients admitted to Hull Royal Infirmary or Castle Hill with IPD between 2002 and 2009 identified
Serotype recorded where available and classified as “low severity”, “high severity” or “other”
Demographic data also collected (sex, age at time of sample and index of multiple deprivation (IMD) score)

8. Results N=553 Mean age 59.4 46% female Mean IMD 31.9 (range 1.6-81.5)
Overall mortality at 30 days, 1 year and 2 years respectively 22.9%, 36.9% and 42.4% respectively

9. Results
Mortality in patients with lower risk serotypes (1, 7F and 8) (n=123) was lower than with higher risk serotypes (3, 6a, 6B, 9N and 19F) (n=75); 11.4% versus 21.3% at 30 days (p =0.012).
At 1 and 2 years p<0.001
Increasing age (p<0.001) and male sex (p=0.003) also associated with increased mortality at 2 years.

10. Mortality rate at 30 days, 1 year and 2 years by Serotype Group

11. Cumulative survival by Serotype Group

12. Conclusions
IPD is associated with increased mortality up to 2 years following infection
Infection with a “high severity” serotype is associated with worse outcome
No evidence that infection with “low severity” serotype is associated with increased long term mortality

13. Discussion
Possible that patients who have infections caused by “high severity” serotypes have a lower barrier to infection due to underlying co-morbid illness
Ongoing work to further establish factors associated with poor long term outcomes
Important to understand the role of serotype for future vaccine development

14. Thank you,
Questions?