Abstract

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.