Population Biology of Streptococcus pneumoniae in West Africa: Multilocus Sequence Typing of Serotypes That Exhibit Different Predisposition to Invasive Disease and Carriage
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Date
2013
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Journal ISSN
Volume Title
Publisher
PLOS ONE
Abstract
Background: Little is known about the population biology of Streptococcus pneumoniae in developing countries, although
the majority of pneumococcal infections occur in this setting. The aim of the study was to apply MLST to investigate the
population biology of S. pneumoniae in West Africa.
Methods: Seventy three invasive and carriage S. pneumoniae isolates from three West African countries including The
Gambia, Nigeria and Ghana were investigated. The isolates covered seven serotypes (1, 3, 5, 6A, 11, 14, 23F) and were
subjected to multilocus sequence typing and antibiotic susceptibility testing.
Results: Overall, 50 different sequence types (STs) were identified, of which 38% (29) were novel. The most common ST was
a novel clone-ST 4012 (6.5%), and some clones including STs 913, 925, 1737, 2160 and 3310 appeared to be specific to the
study region. Two STs including ST 63 and ST 4012 were associated with multiple serotypes indicating a history of serotype
switching. ST 63 was associated with serotypes 3 and 23F, while ST 4012 was associated with serotypes 6A and 23. eBURST
analyses using the stringent 6/7 identical loci definition grouped the 50 STs into 5 clonal complexes and 65 singletons,
expressing a high level of genetic diversity among the isolates. Compared to the other serotypes, serotypes 1 and 5 isolates
appeared to be more clonal. Internationally recognized antibiotic resistant clones of S. pneumoniae were generally absent in
the population investigated and the only multidrug resistant isolate identified (1/66) belong to the Pneumocococcal
Epidemiology Network clone ST 63.
Conclusions: The pneumococcal population in West Africa is quite divergent, and serotypes that are common in invasive
disease (such as serotypes 1 and 5) are more likely to be clonal than serotypes that are common in carriage.
Description
Research Article
Keywords
Biology of Streptococcus pneumoniae, Predisposition, Invasive Disease and Carriage