Seasonality and outbreak of a predominant Streptococcus pneumoniae serotype 1 clone from The Gambia: Expansion of ST217 hypervirulent clonal complex in West Africa

Martin Antonio,David Nsekpong,Ousman Secka,Godwin Enwere,Richard A Adegbola,George Lahai,Abiodun Akisanya,Felicity Cutts,Philip C Hill,Timothy Awine,Tumani Corrah,Kawsu Sankareh,Uzochukwu Egere,Ishrat Hakeem,Syed Ma Zaman,Brian M Greenwood

doi:10.1186/1471-2180-8-198

Martin Antonio, David Nsekpong + Show 14 more

Open Access

https://doi.org/10.1186/1471-2180-8-198

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Abstract

BackgroundStreptococcus pneumoniae serotype 1 causes > 20% of invasive disease, among all age groups combined, in The Gambia. In contrast, it is rarely detected in carriage studies. This study compares the molecular epidemiology of S. pneumoniae serotype 1 causing invasive disease in The Gambia between 1996 and 2005 to those carried in the nasopharynx between 2004 and 2006.ResultsA total of 127 invasive and 36 nasopharyngeal carriage serotype 1 isolates were recovered from individuals of all age groups and were analyzed by serotyping, antibiotic susceptibility testing and MLST. MLST analysis revealed 23 different sequence types (STs), 18 of which were novel. The most prevalent clone among the 163 isolates was ST618 (70.5%), followed by ST3575 (7.4%), ST2084 (2.5%) and ST612 (2.5%). A single ST (ST618), previously shown to belong to the ST217 hypervirulent clonal complex, was frequent among carriage (61.1%) and invasive (72.7%) serotype 1 isolates. ST618 causing both paediatric and adult disease peaked annually in the hot dry season and caused outbreak in 1997 and 2002.ConclusionFor over a decade, isolates of ST618 have been the dominant lineage among serotype 1 carriage and disease isolates circulating in the Gambia. This lineage shows similar epidemiological features to those of the meningococcus in the African meningitis belt being able to cause outbreaks of disease

Highlights

Streptococcus pneumoniae serotype 1 causes > 20% of invasive disease, among all age groups combined, in The Gambia
When more than one isolate was obtained during a single episode of illness, for example from blood and cerebro-spinal fluid (CSF), multiple isolates have been included in the analysis only if they differed by Multi locus sequencing typing (MLST) and/
Despite this we have been able to show convincingly that serotype 1 pneumococci of ST618 are more common in both carriage and invasive disease than serotype 1 pneumococci of other sequence types (STs)

Summary

Introduction

Streptococcus pneumoniae serotype 1 causes > 20% of invasive disease, among all age groups combined, in The Gambia. It is rarely detected in carriage studies. Streptococcus pneumoniae consists of at least 91 different serotypes, the majority of which rarely cause disease; two serotypes (1 and 5) cause > 30% of invasive disease, among all age groups combined, in The Gambia [1]. Faso and Northern Ghana [2,3] It has been associated with outbreaks in crowded or closed communities [46]. It is only rarely detected in carriage studies [7]. A trial of a 9-valent pneumococcal conjugate vaccine in a rural setting in The Gambia showed protective efficacy against radiological pneumonia (37%) and all invasive pneumococcal disease (50%) and reduced all cause hospitalisations and mortality by 15% and 16%

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