Serotype 3 Streptococcus pneumoniae
Genomic comparison of unrelated serotype 3 pneumococcal isolates
In this study, the genomes of three unrelated serotype 3 isolates (ST180, ST458, ST378) have been compared.  This serotype is regarded as an important OM pathogen and has low invasiveness but high mortality.  The current licensed multivalent conjugate vaccines do not offer protection against this serotype and an increase in its prevalence was seen in the US following the introduction of the PCV-7.  ST180 is the most prevalent ST within serotype 3 in Asia, the US and Europe.  The genomes of two serotype 3 ST180 isolates are already publicly available (SP3-BS71, OXC141).  In conrast, ST458 is the most prevalent serotype 3 isolate in Africa and Australian Aboriginal communties.  The genome of a serotype 3 ST458 isolate from a remote Aboriginal community was sequenced using an Illumina Genome Analyser II, along with the genome of the strain WU2 (ST378), which has been used in numerous pneumococcal studies over a 30 year period.  The sequence reads were assembled against the OXC141 genome, allowing genomic comparison of the three STs.  In addition, large contigs which could not align with the reference genome were also analsed identifying accessory regions absent in the OXC141 genome.