title: Discovery of Novel Pneumococcal Serotype 35D, a Natural WciG-Deficient Variant of Serotype 35B.
abstract: Pneumococcus (Streptococcus pneumoniae) remains a significant cause of morbidity and mortality, especially among those at the extremes of age. Its capsular polysaccharide is essential for systemic virulence. Over 90 serologically distinct pneumococcal capsular polysaccharides (serotypes) are recognized, but they are unequal in prevalence. Because antibodies against the capsule are protective, polysaccharide conjugate vaccines, which are constructed against the most prevalent serotypes, have caused great reductions in pneumococcal disease caused by these serotypes. In response, however, the relative prevalences of serotypes have shifted. Certain previously rare serotypes, such as serotype 35B, are increasing in prevalence. Serotype 35B is thus a likely future vaccine candidate, but due to their previous rarity, serotype 35B strains have not been scrutinized for underlying heterogeneity. We studied putative serotype 35B clinical isolates to assess the uniformity of their serological reactions. While most isolates exhibited the accepted serology of serotype 35B, one isolate failed to bind to critical serotyping reagents. We determined that the genetic basis for this aberrant serology was the presence of inactivating mutations in theO-acetyltransferase genewciGComplementation studies in awciGdeletion strain verified that the mutant WciG was nonfunctional, and the serology of the mutant could be restored through complementation with a construct encoding a functional WciG. Nuclear magnetic resonance studies confirmed that the capsule of the WciG-deficient isolate lackedO-acetylation but was otherwise identical to serotype 35B. As this isolate expresses a unique serology with unique biochemistry and a stable genetic basis, we named its novel capsule serotype 35D.
authors.affiliation: Division of Pulmonary, Allergy, and Critical Care Medicine, University of Alabama at Birmingham, Birmingham, Alabama, USA.
authors.forename: K Aaron
authors.initials: KA
authors.lastname: Geno
authors.affiliation: Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, USA.
authors.forename: Jamil S
authors.initials: JS
authors.lastname: Saad
authors.affiliation: Division of Pulmonary, Allergy, and Critical Care Medicine, University of Alabama at Birmingham, Birmingham, Alabama, USA nahm@uab.edu.|Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, USA.
authors.forename: Moon H
authors.initials: MH
authors.lastname: Nahm
mesh_terms: D000123:Acetyltransferases / Q000235:genetics*; D000942:Antigens, Bacterial / Q000276:immunology*; D016667:Bacterial Capsules / Q000276:immunology*; D006801:Humans; D011008:Pneumococcal Infections / Q000276:immunology / Q000382:microbiology; D011135:Polysaccharides, Bacterial / Q000276:immunology*; D065288:Serogroup; D013296:Streptococcus pneumoniae / Q000145:classification / Q000276:immunology* / Q000302:isolation & purification
chemical_list: D000942:Antigens, Bacterial; D011135:Polysaccharides, Bacterial; D000123:Acetyltransferases
keywords: O-acetylation; Streptococcus pneumoniae; capsular polysaccharide; serogroup 35; serotype 35B; serotype 35D