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High levels of recombination among Streptococcus pneumoniae isolates from the Gambia

E S Donkor1, C J Bishop, K A Gould

  • 1Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom.

Mbio
|June 23, 2011
PubMed

Insights

Pneumococcal carriage in Gambian children revealed diverse strains and frequent genetic recombination. High admixture suggests multiple infections may drive recombination, potentially impacting conjugate vaccine effectiveness.

Area of Science:

  • Microbiology
  • Genetics
  • Epidemiology

Background:

  • Streptococcus pneumoniae (pneumococcus) causes significant childhood illness globally.
  • Understanding pneumococcal diversity and genetic exchange is crucial for vaccine development and public health strategies.

Purpose of the Study:

  • To characterize pneumococcal carriage isolates from young children in The Gambia using multilocus sequence typing (MLST).
  • To investigate genetic diversity, capsular switching, antimicrobial resistance, and recombination within these isolates.

Main Methods:

  • Multilocus sequence typing (MLST) was performed on 148 pneumococcal carriage isolates from children under 24 months old.
  • Microarrays were used to detect capsule genes and antimicrobial resistance determinants (tetM).
  • Statistical genetic analysis was employed to assess genetic admixture and recombination.

Main Results:

  • MLST identified 76 distinct sequence types (STs), with STs 802 (serotype 23F) and 919 (serotype 6A) being most common.
  • Eleven STs were novel to Africa; six STs showed evidence of capsular switching.
  • 58% of analyzed isolates harbored the tetM resistance gene; 34% showed significant genetic admixture, higher than in the UK or Finland.

Conclusions:

  • The pneumococcal population in The Gambia is genetically diverse with evidence of frequent capsular switching and recombination.
  • High levels of genetic admixture may result from high rates of multiple pneumococcal carriage.
  • These findings have implications for the population-level impact of pneumococcal conjugate vaccines in the region.

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