Cross-Reactivity of Current Serogroup 6 Factor Sera from Statens Serum Institut with the Recently Described Pneumococcal Serotype 6D

Bratcher, Preston E.; Nahm, Moon H.

doi:10.1128/jcm.00839-10

Cited by 7 publications

(8 citation statements)

References 5 publications

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“…Samples stained with secondary antibody alone were used as negative controls. Although all factor sera displayed some moderate binding to nontarget serotypes, only strong signals correlate with Quellung reaction results (Table 1), consistent with reports of serogroup 6 factor sera binding to bacteria expressing ST 6A, 6B, 6C, and 6D PS capsules (4).…”

Section: Ps Purification and De-o-acetylationsupporting

confidence: 88%

Elucidation of Structural and Antigenic Properties of Pneumococcal Serotype 11A, 11B, 11C, and 11F Polysaccharide Capsules

2011

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Despite the emerging impact of serogroup 11 serotypes in Streptococcus pneumoniae epidemiology, the structures of serogroup 11 capsule types have not been fully elucidated, particularly the locations of O-acetyl substitutions. Here, we report the complete structures of the serotype 11B, 11C, and 11F polysaccharides and a revision to the serotype 11A capsular polysaccharide using nuclear magnetic resonance (NMR). All structures shared a linear, tetrasaccharide backbone with a pendant phosphopolyalcohol. Three of four saccharides are conserved in all serotypes. The individual serotype capsules differed in the identity of one saccharide, the pendant phosphopolyalcohol, and the O-acetylation pattern. Though the assigned locations of O-acetate substitutions in this study differed from those of previous reports, our findings were corroborated with strong correlations to serology and genetics. We examined the binding of serotyping sera to serogroup 11 polysaccharides by using flow cytometry and an inhibition-type enzyme-linked immunosorbent assay (ELISA) and found that de-O-acetylation of capsular polysaccharides by mild hydrolysis decreases its immunoreactivity, supporting the crucial role of O-acetylation in the antigenicity of these polysaccharides. Due to strong correlations between polysaccharide structures and capsule biosynthesis genes, we were able to assign target substrates for the O-acetyltransferases encoded by wcwC, wcwR, wcwT, and wcjE. We identified antigenic determinants for serogroup 11 serotyping sera and highlight the idea that conventional serotyping methods are not capable of recognizing all putative variants of S. pneumoniae serogroup 11.

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Section: Ps Purification and De-o-acetylationsupporting

confidence: 88%

Elucidation of Structural and Antigenic Properties of Pneumococcal Serotype 11A, 11B, 11C, and 11F Polysaccharide Capsules

2011

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“…In serotype 6D, it is assumed that wciN ␤ is inserted into serotype 6B cps loci (2). Thus, it can be speculated that serotype 6D isolates react simultaneously with the factor sera 6c and 6d, which are bound to the serotypes 6B and 6C, respectively, which was confirmed by recent papers (3,8).Recently, we found serotype 6D pneumococcal isolates reacting with factor serum 6b (both absorbed and unabsorbed), which is specific to serotype 6A. As a part of a multinational study on invasive pneumococcal infections, we have collected 244 S. pneumoniae serogroup 6 isolates from 11 Asian countries, South Korea, India, Japan, Hong Kong, Malaysia, the Philippines, Saudi Arabia, Sri Lanka, Taiwan, Thailand, and Vietnam, during 2008 and.…”

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confidence: 64%

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confidence: 58%

Streptococcus pneumoniae Serotype 6D Cross-Reacting with Serotype 6A, 6B, and 6C Factor Sera

Baek¹,

Song

2011

J Clin Microbiol

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ᰔWe read the papers of Bratcher and Nahm (3) and Oftadeh et al. (8) with interest. Both papers reported that Streptococcus pneumoniae serotype 6D isolates react with factor antiserum specific to serotype 6C in addition to that to 6B. Pneumococcal serotype 6C, first reported in 2007, cross-reacts serologically with serotype 6A but is differentiated by a change in the wciN gene (wciN ␤ ) among the cps loci (9). In addition to serotype 6C, the novel serotype 6D has recently been reported in several countries (2,4,6,7). In serotype 6D, it is assumed that wciN ␤ is inserted into serotype 6B cps loci (2). Thus, it can be speculated that serotype 6D isolates react simultaneously with the factor sera 6c and 6d, which are bound to the serotypes 6B and 6C, respectively, which was confirmed by recent papers (3,8).Recently, we found serotype 6D pneumococcal isolates reacting with factor serum 6b (both absorbed and unabsorbed), which is specific to serotype 6A. As a part of a multinational study on invasive pneumococcal infections, we have collected 244 S. pneumoniae serogroup 6 isolates from 11 Asian countries, South Korea, India, Japan, Hong Kong, Malaysia, the Philippines, Saudi Arabia, Sri Lanka, Taiwan, Thailand, and Vietnam, during 2008 and. Serotypes were determined using a conventional Quellung method (Statens Serum Institute, Copenhagen, Denmark). In addition, the serotype-specific PCR method of Jacobs et al. (5) was used to identify serotypes 6C and 6D.Among the 244 invasive S. pneumoniae serogroup 6 isolates, 73, 144, and 13 pneumococcal isolates were identified as serotypes 6A, 6B, and 6C, respectively (Table 1). Fourteen isolates could be identified as serotype 6D because they reacted with the factor sera 6c and 6d and produced 1.8-kb products with the 5106-3101 primer pair set in PCR. This product indicates that the wciN gene of serotype 6B was substituted by the wciN ␤ gene. These S. pneumoniae serotype 6D isolates (13 from South Korea and one from Taiwan) were isolated from sputum, tracheal aspirates, and blood. In addition to reacting with factor sera 6c and 6d, these isolates also reacted with factor serum 6b specific to serotype 6A (Table 1). The 14 pneumococcal isolates reacted simultaneously with factor sera 6b, 6c, and 6d.To our knowledge, no pneumococcal isolates reactive with all the factor sera have hitherto been reported. Oftadeh et al. (8) reported that serotype 6C isolates reacted with unabsorbed factor serum 6b and did not react with absorbed serum and that serotype 6D isolates did not react with both absorbed and unabsorbed sera. However, our serotype 6D isolates reacted with both absorbed and unabsorbed factor serum 6b. It has been suggested that serotype 6D emerged by substitution of the wciN gene with the wciN ␤ gene from serotype 6B isolates (1, 2). However, the present result may indicate that serotype 6D did not arise simply by such a substitution. Even cps loci other than the wciN ␤ gene of serotype 6D may differ from those of serotype 6B, which is supported by the finding that the res...

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“…Since the implementation of the PCR-based serotyping scheme, the separate mPCR for detecting serotype 6C/6D isolates described by Carvalho et al is no longer regularly used at our laboratory in Helsinki, first, because this particular mPCR alone is not able to distinguish between serotypes 6C and 6D, both of which carry the wciN␤ gene, and second, because an antiserum and publications detailing its use are available to differentiate these serotypes (7). The newly identified serotype 6D was incorrectly identified with the methodology under validation (Table 1), but the growing number of publications about the typing of serotype 6D either with the help of antisera or by other PCR-based assays will make it possible to avoid this type of misidentification in the future (6,20,26,27).…”

Section: Discussionmentioning

confidence: 99%

From Quellung to Multiplex PCR, and Back When Needed, in Pneumococcal Serotyping

et al. 2012

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All currently available vaccines against Streptococcus pneumoniae are based on selections of the over 90 different serotypes, which underlines the importance of serotyping for surveillance and vaccine efficacy monitoring. In this study, we modified and validated a PCR-based scheme for deducing the serotypes of the invasive pneumococci isolated in Finland. For validation, 170 isolates were serotyped using the new protocol with six sequential multiplex PCRs for the deduction of serotypes, supplemented with Quellung testing when needed. The results were compared with those obtained by traditional serotyping methods. We found that 98.8% (168/170) of the isolates were correctly serotyped by the new protocol. Subsequently, the scheme was taken into regular use for serotyping the invasive pneumococci isolated in Finland for serotype-specific surveillance purposes and has been applied in the serotyping of more than 1,500 invasive isolates so far. The sequential multiplex PCRs (mPCRs) have given a result for over 99% of the isolates and allowed us to both handle samples in bulk and noticeably reduce the cost of reagents. While serotyping primarily by PCR is precise and effective, Quellung testing remains the most reliable way to discover possible discrepancies between the DNA deduced and the phenotypic serotype of an isolate. Since implementing the protocol for regular use, two serotype 19F PCR-positive isolates were found to be serotype 19A by the Quellung reaction. While a rare occurrence, this is an important observation, which prompted a revision of our serotyping protocol to prevent possible underreporting of serotype 19A, a potential replacement serotype following large-scale vaccination.

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Cross-Reactivity of Current Serogroup 6 Factor Sera from Statens Serum Institut with the Recently Described Pneumococcal Serotype 6D

Cited by 7 publications

References 5 publications

Elucidation of Structural and Antigenic Properties of Pneumococcal Serotype 11A, 11B, 11C, and 11F Polysaccharide Capsules

Elucidation of Structural and Antigenic Properties of Pneumococcal Serotype 11A, 11B, 11C, and 11F Polysaccharide Capsules

Streptococcus pneumoniae Serotype 6D Cross-Reacting with Serotype 6A, 6B, and 6C Factor Sera

From Quellung to Multiplex PCR, and Back When Needed, in Pneumococcal Serotyping

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