Capsular-type prediction by phylogenetic tree of glycosyltransferase gene polymorphism in Streptococcus pneumoniae

Abstract

Capsular-type prediction by phylogenetic tree of glycosyltransferase gene polymorphism in Streptococcus pneumoniae Yuka Tomita1,2, Akira Okamoto2, Keiko Yamada2, Testuya Yagi3, Yoshinori Hasegawa4, Michio Ohta21Department of Infectious Disease, Nagoya University Hospital, 2Department of Bacteriology, Nagoya University Graduate School of Medicine, 3Center of National University Hospital for Infection Control, Nagoya University Hospital, 4Department of Respiratory Medicine, Nagoya University Graduate School of Medicine, Nagoya, JapanAbstract: Streptococcus pneumoniae can cause severe infections among children and the elderly. Molecular capsule typing is being investigated extensively as a replacement of conventional serotyping using antisera. We focused on the glycosyltransferase (GT) genes in the capsular polysaccharide synthesis (cps) gene cluster of S. pneumoniae for classification of capsular types. The Sanger Institute provided sequences of the cps loci of 90 serotypes of S. pneumoniae. Each cps locus contained 1–6 putative GT genes per strain, for a total of 352 GT genes. Phylogenetic analysis of GT gene polymorphisms distinguished 90 serotypes into 64 phylogenetic groups. However, the sequence data contained only one sample from each serotype. Therefore, we selected six clinical isolates belonging to serogroup 6 and seven clinical isolates belonging to serotype 19F by antisera and sequenced GT genes. From phylogenetic analysis, these sequences were very similar to those of the Sanger Institute, and we can use GT genes as serotype-specific genes.Keywords: Streptococcus pneumoniae, phylogenetic tree, glycosyltransferase gene