Rapid identification of Streptococcus pneumoniae serotypes by cpsB gene-based sequetyping combined with multiplex PCR

BACKGROUND/PURPOSE

Streptococcus pneumoniae is an important human pathogen that causes invasive infections in adults and children. Accurate serotyping is important to study its epidemiological distribution and to assess vaccine efficacy.

METHODS

Invasive S. pneumoniae isolates (n = 300) from 27 teaching hospitals in China were studied. The Quellung reaction was used as the gold standard to identify the S. pneumoniae serotypes. Subsequently, multiplex PCR and cpsB gene-based sequetyping methods were used to identify the serotypes.

RESULTS

Based on the Quellung reaction, 299 S. pneumoniae isolates were accurately identified to the serotype level and 40 different serotypes were detected. Only one strain was non-typeable, and five most common serotypes were identified: 23F (43, 14.3%), 19A (41, 13.7%), 19F (41, 13.7%), 3 (31, 10.3%), and 14 (27, 9.0%). Overall, the multiplex PCR method identified 73.3 and 20.7% of the isolates to the serotype and cluster levels, respectively, with 1.7% of the isolates misidentified. In contrast, the cpsB sequetyping method identified 59.0 and 30.3% of the isolates to the serotype and cluster levels, respectively, and 7% were misidentified.

CONCLUSIONS

The cpsB gene sequetyping method combined with multiplex PCR, can greatly improve the accuracy and efficiency of serotyping, besides reducing the associated costs.

Streptococcus pneumoniae serotype epidemiology among PCV-10 vaccinated and unvaccinated children at Gertrude's Children's Hospital, Nairobi County: a cross-sectional study

Background:Streptococcus pneumoniae (SP n) serotype replacement and emergence of multidrug resistant SP n has exacerbated the need for continuous regional serotype surveillance. We investigated SP n serotypes circulating among children ≤5 years in Nairobi County. Methods:Streptococcus pneumoniae stocks stored at -70°C in brain heart infusion medium were thawed at room temperature for 30 minutes. In total, 10 µl of the stored SP n cells were suspended in 50 µl PBS and gently vortexed. About 10 µl of the suspended cells were added on to a glass slide and mixed with 10 µl pooled antisera. The glass slide was swirled gently while observing for any reaction. The process was repeated with individual groups under various antisera pools. Those serotypes that did not belong to any pool were typed directly until a positive agglutination reaction was observed. The cells/PBS/serotype-specific antisera mixture on the glass slide were covered with a coverslip and observed under a phase contrast microscope at ×100 objective lens with oil emulsion. Results: Out of the 206 subjects sampled, 20.39% (n=42) were found to be carriers of SP n. About 52% (n=22) of the SP n carriers had received the recommended dose of PCV-10, while 48% (n=20) of the carriers had not. Almost all (n=41; 19.90% of subjects) isolates contained non-vaccine type SP n serotypes, while n=1 of the serotypes (in 0.49% of subjects) were untypeable. Serotypes 28F, 6A, 11A, 3 and 7C were prevalent in both vaccinated and unvaccinated children, whereas serotypes 23A, 17F, 35F, 48, 13 and 35B, and 23B, 20, 19B, 21, untypeable, 15B and 39 were found among unvaccinated and vaccinated groups, respectively. Conclusions: All SP n serotypes isolated from the subjects sampled were non PCV-10 vaccine type. Therefore Kenyan children receiving PCV-10 vaccine are not protected.

Streptococcus pneumoniae Serotype Epidemiology among PCV-10 Vaccinated and Unvaccinated Children at Gertrude's Children's Hospital, Nairobi County: A Cross-Sectional Study

Background: Serotype replacement and emergence of multidrug resistant S. pneumoniae has exacerbated the need for continuous regional serotype surveillance especially in the developing world. We investigated S. pneumoniae serotypes circulating among vaccinated and unvaccinated children ≤5 years in Nairobi County post PCV10 era. Methods: A total of 206 vaccinated and unvaccinated children attending Gertrude's Children's Hospital (GCH) were recruited for this study. Nasopharyngeal swabs collected using Copan Flocked Swabs were the main study specimen. Culturing and isolation of S. pneumoniae was done on BA with gentamicin and BA plates respectively at the GCH main laboratory. Serotyping was done using the Quellung reaction at the KEMRI-Wellcome Trust, Kilifi.  Results: Out of the 206 subjects sampled, 20.39% (42) were found to be carriers of S. pneumoniae. About 52% (n=22) of the S. pneumoniae carriers had received the recommended dose of PCV-10, while 48% (n=20) of the carriers had not. Almost all (n=41; 19.90% of subjects) isolates contained non-vaccine type S. pneumoniae serotypes, while n=1 of the serotypes (in 0.49% of subjects) were untypeable. Serotypes 28F, 6A, 11A, 3 and 7C were prevalent in both vaccinated and unvaccinated children, whereas serotypes 23A, 17F, 35F, 48, 13 and 35B, and 23B, 20, 19B, 21, untypeable, 15B and 39 were found among unvaccinated and vaccinated groups, respectively. Conclusions: All S. pneumoniae serotypes isolated from the subjects sampled were non PCV-10 vaccine type. These results therefore highlight the importance of monitoring and evaluation to provide epidemiological information to determine the effectiveness of PCV10 in Kenya's Public health services.

Discovery of Streptococcus pneumoniae serogroup 35 variants in Australian patients

OBJECTIVES

Streptococcus pneumoniae isolates from Australian invasive pneumococcal disease cases displaying an atypical 35B phenotype. Whole genome sequencing was used to analyse these strains and identify changes to the capsule gene regions.

METHODS

Four atypical serogroup 35 isolates from Australian reference laboratories were unable to be assigned to one of the four known group 35 serotypes by the Quellung serotyping method. Genetic characterization of the capsule locus was performed by bioinformatic analysis of whole genome sequencing data for all isolates.

RESULTS

Genetic analysis identified four independent disruptions to the wciG gene, which encodes an O-acetyltransferase responsible for the O-acetylation of the 6Galβ1 residue in the capsular polysaccharide repeat unit of serotype 35B.

CONCLUSIONS

This is the first published report on the incidence and capsular gene characteristics of a S. pneumoniae 35B variant.

Capsular typing of Streptococcus pneumoniae isolated in an Algerian hospital using a new multiplex PCR-based scheme

We developed a new sequential multiplex-PCR-based typing scheme (MPBTS) for pneumococcal capsular classification. The serogroup/type of 37 control isolates obtained by the Quellung reaction, MPBTS, and nucleotide sequencing, were fully concordant. The serogroups/types of 75 invasive isolates determined by MPBTS, presented 100% specificity and 96% sensitivity, when compared with the Quellung reaction.