Genome evolution driven by host adaptations results in a more virulent and antimicrobial-resistant Streptococcus pneumoniae serotype 14.
BACKGROUND
Streptococcus 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).


RESULTS
Comparative 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.


CONCLUSIONS
The 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.
Ding
Feng
F
The CAS Key Laboratory of Genome Sciences and Information, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing, PR China. dingfeng@big.ac.cn
Tang
Petrus
P
Hsu
Mei-Hua
MH
Cui
Peng
P
Hu
Songnian
S
Yu
Jun
J
Chiu
Cheng-Hsun
CH
D000222:Adaptation, Physiological / Q000235:genetics; D004251:DNA Transposable Elements; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D019143:Evolution, Molecular; D022761:Gene Transfer, Horizontal / Q000235:genetics; D016680:Genome, Bacterial; D046915:Penicillin-Binding Proteins / Q000235:genetics; D013296:Streptococcus pneumoniae / Q000145:classification / Q000187:drug effects / Q000235:genetics* / Q000472:pathogenicity; D014774:Virulence
D004251:DNA Transposable Elements; D046915:Penicillin-Binding Proteins