Carriage of Streptococcus pneumoniae and other respiratory bacterial pathogens in low and lower-middle income countries: a systematic review and meta-analysis.

Effua Usuf,Bernard Hoet,Brian M. Greenwood,Richard A. Adegbola,Sean D. Reid,Philip C. Hill,Anna Roca,Rodrigo DeAntonio

doi:10.1371/journal.pone.0103293

Abstract

BackgroundInfection with Streptococcus pneumoniae is a major cause of childhood morbidity and mortality worldwide, especially in low income countries where pneumococcal conjugate vaccines (PCVs) are still underused. In countries where PCVs have been introduced, much of their efficacy has resulted from their impact on nasopharyngeal carriage in vaccinated children. Understanding the epidemiology of carriage for S. pneumoniae and other common respiratory bacteria in developing countries is crucial for implementing appropriate vaccination strategies and evaluating their impact.Methods and FindingsWe have systematically reviewed published studies reporting nasopharyngeal or oropharyngeal carriage of S. pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, Staphylococcus aureus, and Neisseria meningitidis in children and adults in low and lower-middle income countries. Studies reporting pneumococcal carriage for healthy children <5 years of age were selected for a meta-analysis. The prevalences of carriage for S. pneumoniae, H. influenzae, and M. catarrhalis were generally higher in low income than in lower-middle income countries and were higher in young children than in adults. The prevalence of S. aureus was high in neonates. Meta-analysis of data from young children before the introduction of PCVs showed a pooled prevalence estimate of 64.8% (95% confidence interval, 49.8%–76.1%) in low income countries and 47.8% (95% confidence interval, 44.7%–50.8%) in lower-middle income countries. The most frequent serotypes were 6A, 6B, 19A, 19F, and 23F.ConclusionsIn low and lower-middle income countries, pneumococcal carriage is frequent, especially in children, and the spectrum of serotypes is wide. However, because data are limited, additional studies are needed to adequately assess the impact of PCV introduction on carriage of respiratory bacteria in these countries.

Highlights

Streptococcus pneumoniae is a major cause of invasive diseases and respiratory tract infections and caused approximately 500,000 deaths in children,5 years of age in 2008, mostly in low income countries [1,2]
Since 2000, the introduction of the 7-valent pneumococcal conjugate vaccine (PCV-7,) and second generation pneumococcal conjugate vaccines (PCVs) has significantly reduced the burden of invasive pneumococcal disease (IPD) in vaccinated children [4
Results of the literature search We identified 485 articles related to carriage of potentially pathogenic bacteria from PubMed; 93 were retrieved for assessment of the full text (Figure 1)

Summary

Introduction

Streptococcus pneumoniae (the pneumococcus) is a major cause of invasive diseases and respiratory tract infections and caused approximately 500,000 deaths in children ,5 years of age in 2008, mostly in low income countries [1,2]. Asymptomatic nasopharyngeal carriage, which plays an essential role in the transmission of S. pneumoniae, usually precedes invasive pneumococcal disease (IPD) [3]. The indirect (or herd) effects of PCVs against IPD are driven primarily by their impact on carriage of vaccinetype (VT) pneumococci in vaccinated children, preventing transmission to unvaccinated contacts [13–15]. Infection with Streptococcus pneumoniae is a major cause of childhood morbidity and mortality worldwide, especially in low income countries where pneumococcal conjugate vaccines (PCVs) are still underused. In countries where PCVs have been introduced, much of their efficacy has resulted from their impact on nasopharyngeal carriage in vaccinated children. Understanding the epidemiology of carriage for S. pneumoniae and other common respiratory bacteria in developing countries is crucial for implementing appropriate vaccination strategies and evaluating their impact

Methods

Results

Discussion

Conclusion