Genetic Basis for the New Pneumococcal Serotype, 6C

Abstract

We have recently reported a new pneumococcal serotype (6C), which is closely related to serotype 6A (I. H. Park et al., J. Clin. Microbiol. 45:1225-1233, 2007). To investigate the genetic basis for serotype 6C, we studied the capsule gene loci of 14 6C isolates from three different continents, including one isolated in Alabama 27 years ago. The wciN region of all 6C isolates has a 1,029-bp-long sequence that replaces the 1,222-bp-long sequence of the 6A wciN region. This recombination event has created a new 1,125-bp-long open reading frame which encodes a product that is also homologous to glycosyl transferases. Flanking this introduced gene is 300 bp upstream and 100 bp downstream with only about 90% homology with 6A and which is identical in all 6C isolates. Transfer of the wciN region converts 6A to 6C. Determination of the DNA sequence of the entire capsule gene locus of one 6C isolate showed that the 6C capsule gene locus is almost identical (>98% homologous) to that of 6A except for the wciN region. These findings indicate that the 6C capsule type originated more than 27 years ago by a single recombination event in a 6A locus in which 6A wciN was replaced by a gene of unknown origin.

Discovery of Streptococcus pneumoniae Serotype 6 Variants with Glycosyltransferases Synthesizing Two Differing Repeating Units

“…Site-directed Mutagenesis-Mutant pneumococcal strains were made by transforming TIGR6A with appropriate genetic constructs as described (11). An unencapsulated variant, named MBO163, was made by allelic exchange of the wchAwciN-wciO gene region with a Janus cassette (Cassette 1) (see Fig.…”

“…1). Reflecting this structural difference, the capsule gene (cps) loci of serotypes 6A and 6B have wciN␣ encoding a galactosyltransferase, whereas serotypes 6C and 6D have wciN␤, which is distinct from wciN␣ and encodes a glucosyltransferase (11).…”

Carriage ofStreptococcus pneumoniae3 Years after Start of Vaccination Program, the Netherlands

“…Briefl y, swabs were cultured for S. pneumoniae, then 1 pneumococcal colony per plate was subcultured and serotyped by the capsular swelling method (Quellung reaction). All serotype 6A isolates were submitted to the National Reference Laboratory of Bacterial Meningitis (Academic Medical Center, Amsterdam) for further discrimination between 6A and the newly discovered serotype 6C by PCR with primers 5106 and 1301 and primers 6C-fwd and 6C-rev (16). Results were confi rmed by the Quellung reaction with newly available antiserum to identify 6C serotype (Statens Serum Institute, Copenhagen, Denmark).…”

Drastic changes in serotypes of carried pneumococci due to an increased vaccination rate in Hungary

“…A pneumococcus legfontosabb antigénje a poliszacharid tok, aminek alapján ma már 93 különböző szerotípust különböztetünk meg [5,6]. A védőoltások ebből a 93-ból a 7 (Prevenar; PCV-7), 13 (PCV-13), illetve 23 (Pneumovax; PS-23) leggyakoribb tisztított tok poliszacharidot tartalmazzák.…”