Streptococcus Pneumoniae septic arthritis in adults in Bristol and Bath, United Kingdom, 2006–2018: a 13-year retrospective observational cohort study

Catherine Hyams,Zahin Amin-Chowdhury,Norman K Fry,Paul North,Adam Finn,Andrew Judge,Shamez N Ladhani,O Martin Williams

doi:10.1080/22221751.2021.1945955

Abstract

ABSTRACT Few studies on adult pneumococcal septic arthritis are sufficiently large enough to assess both epidemiological trends following routine pneumococcal immunization and clinical disease. With major shifts in serotypes causing invasive pneumococcal disease (IPD), we wanted to determine the clinical phenotype of adult septic arthritis caused by Streptococcus pneumoniae. We conducted a retrospective cohort study of pneumococcal infections in Bristol and Bath, UK, 2006–2018. We defined pneumococcal septic arthritis as adults with clinically-confirmed septic arthritis, with pneumococcus isolated from sterile-site culture or urinary antigen test positivity. Clinical records were reviewed for each patient in the cohort. Septic arthritis accounted for 1.7% of all IPD cases. 45 cases of adult pneumococcal septic arthritis occurred, with disease typically affecting older adults and those with underlying comorbidity. 67% patients had another focus of infection during their illness. 66% patients required increased care on discharge and 43% had reduced range of movement. In-hospital case fatality rate was 6.7%. One-year patient mortality was 31%. Currently most cases of adult pneumococcal septic arthritis are due to non-PCV13 serotypes which are associated with more severe disease. Non-PCV-13 serotypes had higher prevalence of concomitant pneumococcal infection at another site (73.7% versus 36.6%), increased intensive care or high-dependency unit requirement (32.4% versus 0%), and increased inpatient and 1-year case fatality rate (8.8% versus 0%, and 32.4% versus 27.4% respectively) compared to PCV-13 serotypes. Pneumococcal septic arthritis remains a small proportion of IPD. However, there is significant associated morbidity and mortality, and pneumococcal septic arthritis requires monitoring in coming years.

Highlights

The annual incidence of septic arthritis in adults in Western Europe ranges between 4–10 per 100,000 patient-years and appears to be increasing [1,2]
Annual blood and joint cultures increased by 38% and 23% respectively from 2006 to 2018, with the increase in testing less than the increase in pneumococcal septic arthritis detected in hospitalised patients
We have described one of the largest cohorts of patients with pneumococcal septic arthritis occurring over 13 years in South West England

Summary

Introduction

The annual incidence of septic arthritis in adults in Western Europe ranges between 4–10 per 100,000 patient-years and appears to be increasing [1,2]. Septic arthritis is associated with significant morbidity and long-term disability, with case fatality rates (CFR) up to 15% [1,3,4]. Infection can spread locally, damaging bones and nerves, and potentially cause systemic sepsis [6]. Treatment involves empirical antibiotic therapy and removal of the infection source. Staphylococcus aureus is the commonest cause of septic arthritis, causing 30-50% cases. Streptococcus pneumoniae is a recognised but rare cause of septic arthritis, causing 24% cases, with a higher prevalence in some cohorts [7,8]. Over 100 pneumococcal serotypes are recognised, with the unique capsular polysaccharide of certain serotypes being the antigenic targets in current vaccines. Two vaccines are currently used in the UK.

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