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Evaluation of serotype prediction by cpsA-cpsB gene polymorphism in Streptococcus pneumoniae
E R Lawrence1, C A Arias, B Duke
1Department of Medical Microbiology, St. Bartholomew's and the Royal London School of Medicine and Dentistry, London E1 2AD, United Kingdom.
Insights
A new PCR method can predict Streptococcus pneumoniae serotypes, aiding surveillance before, during, and after new conjugate vaccine introduction. This tool helps monitor pneumococcal serotype prevalence and vaccine effectiveness.
Area of Science:
- Microbiology
- Vaccinology
- Molecular Biology
Background:
- New pneumococcal conjugate vaccines (PCVs) are being introduced, necessitating monitoring of Streptococcus pneumoniae serotype prevalence.
- The impact of PCVs on the relative importance of different pneumococcal serotypes remains unknown.
- Effective surveillance strategies are crucial for tracking serotype shifts post-vaccine introduction.
Purpose of the Study:
- To evaluate a PCR-based method for predicting pneumococcal serotypes from clinical isolates.
- To assess the utility of this PCR method for surveillance of Streptococcus pneumoniae serotypes.
Main Methods:
- A PCR method targeting polymorphisms in two common capsule locus genes was developed.
- The method was applied to 93 clinical isolates of Streptococcus pneumoniae collected in 1997.
- Serotype predictions were compared against culture-based identification.
Main Results:
- The PCR method correctly predicted 65 out of 70 vaccine serotypes, improving to 69 with additional patterns.
- 19 out of 23 non-vaccine serotypes were correctly identified.
- A discrepancy was noted for four isolates of serotype 6A (non-vaccine) and 6B (vaccine).
Conclusions:
- The PCR method shows promise for predicting Streptococcus pneumoniae serotypes.
- This technique could be valuable for direct application to clinical specimens, aiding serotype surveillance.
- The method offers a potential tool for monitoring pneumococcal epidemiology in the context of new vaccine introductions.
Abstract:
New pneumococcal conjugate vaccines covering a limited number of serotypes are likely to come into widespread use over the next few years. It is unknown what effect this will have on the relative importance of different serotypes as causes of pneumococcal infection. Hence, it will be important to monitor serotype prevalence before, during, and after the introduction of new vaccines. We have investigated the ability of a PCR method based on polymorphisms in two genes common to the different capsule loci to predict the serotype of 93 clinical isolates of Streptococcus pneumoniae submitted to the Central Public Health Laboratory in 1997. Of 70 isolates with vaccine serotypes, 65 were predicted to belong to the correct serotype; this number was improved to 69 with the inclusion of two additional patterns to the database. Of 23 isolates with other serotypes, 19 were correctly predicted as non-vaccine serotypes, the discrepancy lying with four isolates of 6A (non-vaccine serotype) that were indistinguishable from isolates of 6B (vaccine serotype). In situations in which culture of the organism is not feasible, this method could potentially be applicable directly to clinical specimens and could be a valuable aid to the surveillance of pneumococcal serotypes.