COMPUTATIONAL SEROTYPING OF STREPTOCOCCUS PNEUMONIAE STRAINS BASED ON CAPSULAR GENETIC LOCI AND POLYMERASE GENE THROUGH PHYLOGENETIC ANALYSIS
Jothi Ramalingam* and Balamurugan Sivaprakasam
ABSTRACT
Streptococcus pneumoniae has about ninety serotypes, each serotype
specific capsule is made up of a unique polysaccharide and nearly 20
genes in a genetic locus are involved in its synthesis. Despite the
diversity of capsular polysaccharides, the genetic loci of all serotypes
exhibit a similar organization, but few genes including polymerase are
unique to given serotypes. Generally, one of the pneumococcal vaccine
is derived from capsular polysaccharide. But the wide variation in
capsular types and discrepancies in the conventional serotyping make
most of the available vaccines ineffective. Typing of pneumococcal
strains into effective and accurate serotypes without discrimination is
inevitable in developing effective pneumococcal vaccines. The present
study considered capsular genetic loci and polymerase genes of ninety
serotypes for sequence based computational serotyping through phylogenetic analysis. The
study reveals that serotypes from the serogroups 7,9,15,16,19,23,33,35,41 and 47 have
genetic differences which are very different from the results of conventional serotyping
methods. Similarly, the identical serotypes among serogroups 40/7F/7A; 38/25F/25A and
37/33F/33A are in contrast to the differences revealed by conventional serotyping methods. It
provides an understanding about the diversification of capsular polysaccharides and the
importance of developing effective vaccines.
Keywords: Streptococcus pneumoniae, serotyping, capsular genetic loci, polymerase, phylogenetic analysis.
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