Abstract
Group B Streptococcus (GBS) is an encapsulated, gram-positive pathogen that is an important cause of neonatal invasive infections, including sepsis and meningitis. There are ten known GBS serotypes based on distinct capsule compositions (Ia, Ib, II-IX), and current candidate capsular polysaccharide conjugate vaccines target only a subset of these. Serotyping of GBS isolates is important for understanding local epidemiology and for monitoring for serotype replacement or capsular switching. However, serotyping generally requires either latex agglutination, multiplex PCR with analysis of band sizes, or analysis of whole genome sequences–all techniques that are either expensive or not widely available. Here we report the development of a robust real-time PCR assay for determining GBS serotypes. Using both a diverse reference set of strains encompassing all ten serotypes and a collection of clinical isolates, we demonstrate concordance between real-time PCR serotyping and latex agglutination. We propose that real-time PCR serotyping represents an attractive alternative to current serotyping methods and may allow for improved acquisition of GBS serotype data.
Highlights
Streptococcus agalactiae (Group B Streptococcus [GBS]) is a major cause of neonatal morbidity and mortality worldwide[1,2]
(≥3 per serotype) from the Centers for Disease Control and Prevention (CDC) Streptococcus laboratory to determine whether the primer/probe combinations
As the development of vaccines that target a subset of the ten known GBS serotypes proceeds, it will become increasingly important to understand the distribution of vaccine and non-vaccine serotypes and to monitor for capsular switching and serotype replacement
Summary
Streptococcus agalactiae (Group B Streptococcus [GBS]) is a major cause of neonatal morbidity and mortality worldwide[1,2]. While the incidence of GBS early-onset sepsis has decreased substantially in the United States following the implementation of universal screening and intrapartum antimicrobial prophylaxis[3,4], these represent resource-intensive policies that are subject to missed opportunities for prevention[5,6]. Because of these limitations, improved methods for prevention of GBS disease are urgently needed. We describe a novel TaqMan-based real-time PCR strategy for serotyping GBS based on detection of specific cps locus sequences and demonstrate its applicability using both a defined set of strains from a reference laboratory and a set of primary clinical isolates
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