Abstract
BackgroundStreptococcus pneumoniae serotype 14 is one of the most common pneumococcal serotypes that cause invasive pneumococcal diseases worldwide. Serotype 14 often expresses resistance to a variety of antimicrobial agents, resulting in difficulties in treatment. To gain insight into the evolution of virulence and antimicrobial resistance traits in S. pneumoniae from the genome level, we sequenced the entire genome of a serotype 14 isolate (CGSP14), and carried out comprehensive comparison with other pneumococcal genomes. Multiple serotype 14 clinical isolates were also genotyped by multilocus sequence typing (MLST).ResultsComparative genomic analysis revealed that the CGSP14 acquired a number of new genes by horizontal gene transfer (HGT), most of which were associated with virulence and antimicrobial resistance and clustered in mobile genetic elements. The most remarkable feature is the acquisition of two conjugative transposons and one resistance island encoding eight resistance genes. Results of MLST suggested that the major driving force for the genome evolution is the environmental drug pressure.ConclusionThe genome sequence of S. pneumoniae serotype 14 shows a bacterium with rapid adaptations to its lifecycle in human community. These include a versatile genome content, with a wide range of mobile elements, and chromosomal rearrangement; the latter re-balanced the genome after events of HGT.
Highlights
Streptococcus pneumoniae serotype 14 is one of the most common pneumococcal serotypes that cause invasive pneumococcal diseases worldwide
The majority of hemolytic uremic syndrome (HUS) cases are associated with enterohemorrhagic Escherichia coli; HUS associated with invasive S. pneumoniae infection has been increasingly reported over the years, always with a high mortality and long-term morbidity [6]
S. pneumoniae has been evolving rapidly over time, resulting in a large amount of genetic diversity, despite the constraints imposed by the small genome size and complex genetic organization of the genome
Summary
Streptococcus pneumoniae serotype 14 is one of the most common pneumococcal serotypes that cause invasive pneumococcal diseases worldwide. To gain insight into the evolution of virulence and antimicrobial resistance traits in S. pneumoniae from the genome level, we sequenced the entire genome of a serotype 14 isolate (CGSP14), and carried out comprehensive comparison with other pneumococcal genomes. Since 1990 antimicrobial resistance has been escalating in S. pneumoniae [2], resulting in difficulties in the treatment of pneumococcal infections. In the pre-vaccine era, serotype 14 was one of the most common serotypes of S. pneumoniae that caused invasive pneumococcal diseases worldwide [9,10,11]. A total of twelve draft sequences have been published recently [16,17] These pneumococcal genomes provide us a good opportunity to undertake comprehensive comparative studies on the virulence and antimicrobial resistance mechanisms of this microorganism. The diversity and dynamics of the distributed genome of S. pneumoniae serotype 14, especially the mobile genetic elements carrying a number of virulence genes and antimicrobial resistance determinants, are highlighted
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