title: Capsular polysaccharide gene diversity of pneumococcal serotypes 6A, 6B, 6C, and 6D.
abstract: This study was performed to better understand the genetic diversity and evolutionary relatedness of pneumococcal serotypes 6A, 6B, 6C, and 6D. Multi-locus sequence typing (MLST) was performed for 160 serogroup 6 isolates from clinical specimens collected from children between 1991 and 2010. We identified 38 sequence types (STs) comprising five clonal complexes with 12 singletons. Although most STs were confined to a single serotype, some STs were shared by two serotypes, and one ST was shared by three serotypes. Many STs of serotype 6A showed genetic relatedness with those of serotype 6C or 6D in eBURST analysis. Five capsular polysaccharide (cps) genes - wchA, wciO, wciP, wzy, and wzx - were analysed in 74 isolates from our clinical samples and in 36 isolates from GenBank. There were several profiles and clades in each serotype on the analysis of the concatenated sequences of the five cps genes. Small genetic distances between serotypes 6A and 6B and between serotypes 6C and 6D were observed while serotype 6B with an indel sequence formed a distinct clade. When comparing the individual cps genes between the serotypes, there was also a high level of similarity in the wchA and wciO gene sequences between serotype 6C and serotype 6D. On the other hand, serotypes 6A and 6D had the most highly similar wzy and wzx gene sequences. The wzy sequences of serotype 6C were nearly identical (99.6%) to those of serotype 6A clade II strains. In conclusion, we revealed the diversity of the genetic background and cps sequences in each pneumococcal serotype of serogroup 6. Pneumococcal serotype diversity might be attributable to complex serial mutation and recombination events.
authors.affiliation: Department of Pediatrics, Seoul National University College of Medicine, Seoul, Republic of Korea; Department of Pediatrics, Chung-Ang University College of Medicine, Seoul, Republic of Korea.
authors.forename: Ki Wook
authors.initials: KW
authors.lastname: Yun
authors.affiliation: Department of Pediatrics, Seoul National University College of Medicine, Seoul, Republic of Korea; Department of Pediatrics, Chungnam National University Hospital, Daejeon, Republic of Korea.
authors.forename: Eun Young
authors.initials: EY
authors.lastname: Cho
authors.affiliation: Department of Pediatrics, Seoul National University College of Medicine, Seoul, Republic of Korea; Department of Pediatrics, Seoul National University Children's Hospital, Seoul, Republic of Korea.
authors.forename: Eun Hwa
authors.initials: EH
authors.lastname: Choi
authors.affiliation: Department of Pediatrics, Seoul National University College of Medicine, Seoul, Republic of Korea; Department of Pediatrics, Seoul National University Children's Hospital, Seoul, Republic of Korea. Electronic address: hoanlee@snu.ac.kr.
authors.forename: Hoan Jong
authors.initials: HJ
authors.lastname: Lee
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D005260:Female; D014644:Genetic Variation; D005838:Genotype; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008969:Molecular Sequence Data; D058885:Multilocus Sequence Typing; D011008:Pneumococcal Infections / Q000382:microbiology; D011135:Polysaccharides, Bacterial / Q000235:genetics*; D017422:Sequence Analysis, DNA; D065288:Serogroup; D013296:Streptococcus pneumoniae / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification
chemical_list: D004269:DNA, Bacterial; D011135:Polysaccharides, Bacterial
keywords: Capsular polysaccharide gene; Multi-locus sequence typing; Phylogenetic analysis; Serogroup 6; Streptococcus pneumoniae