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Updated: Jun 3, 2026
Capsular Serotyping of Streptococcus pneumoniae by Latex Agglutination
Published on: September 25, 2014
Improved detection of nasopharyngeal cocolonization by multiple pneumococcal serotypes by use of latex agglutination
Paul Turner1, Jason Hinds, Claudia Turner
1Shoklo Malaria Research Unit, Mae Sot, Thailand. pault@tropmedres.ac
Abstract:
Identification of Streptococcus pneumoniae in the nasopharynx is critical for an understanding of transmission, estimates of vaccine efficacy, and possible replacement disease. Conventional nasopharyngeal swab (NPS) culture and serotyping (the WHO protocol) is likely to underestimate multiple-serotype carriage. We compared the WHO protocol with methods aimed at improving cocolonization detection. One hundred twenty-five NPSs from an infant pneumococcal-carriage study, containing ≥ 1 serotype by WHO culture, were recultured in duplicate. A sweep of colonies from one plate culture was serotyped by latex agglutination. DNA extracted from the second plate was analyzed by S. pneumoniae molecular-serotyping microarray. Multiple serotypes were detected in 11.2% of the swabs by WHO culture, 43.2% by sweep serotyping, and 48.8% by microarray. Sweep and microarray were more likely to detect multiple serotypes than WHO culture (P < 0.0001). Cocolonization detection rates were similar between microarray and sweep, but the microarray identified the greatest number of serotypes. A common serogroup type was identified in 95.2% of swabs by all methods. WHO methodology significantly underestimates multiple-serotype carriage compared to these alternate methods. Sweep serotyping is cost-effective and field deployable but may fail to detect serotypes at low abundance, whereas microarray serotyping is more costly and technology dependent but may detect these additional minor carried serotypes.
Insights
Standard nasopharyngeal swab culture methods likely miss multiple Streptococcus pneumoniae serotypes. Advanced techniques like sweep serotyping and microarray analysis reveal significantly higher rates of co-colonization, crucial for understanding transmission and vaccine effectiveness.
Area of Science:
- Microbiology
- Epidemiology
- Vaccinology
Background:
- Accurate identification of Streptococcus pneumoniae carriage in the nasopharynx is vital for tracking disease transmission, assessing vaccine efficacy, and monitoring for potential replacement diseases.
- Conventional methods, such as the World Health Organization (WHO) protocol using nasopharyngeal swab (NPS) culture and serotyping, may underestimate the prevalence of multiple serotypes carried simultaneously (co-colonization).
Purpose of the Study:
- To compare the effectiveness of the standard WHO protocol with alternative methods for detecting multiple Streptococcus pneumoniae serotypes in nasopharyngeal carriage.
- To evaluate the sensitivity of sweep serotyping and molecular-serotyping microarray in identifying co-colonization compared to traditional culture methods.
Main Methods:
- One hundred twenty-five NPS samples from an infant carriage study were re-cultured.
- Sweep serotyping using latex agglutination and molecular-serotyping microarray analysis were performed on the re-cultured samples.
- Results were compared with the standard WHO culture and serotyping protocol.
Main Results:
- Multiple serotypes were detected in 11.2% of swabs by WHO culture, 43.2% by sweep serotyping, and 48.8% by microarray.
- Both sweep serotyping and microarray significantly outperformed WHO culture in detecting multiple serotypes (P < 0.0001).
- Microarray identified the highest number of serotypes, while sweep serotyping offered a cost-effective, field-deployable alternative, though potentially missing low-abundance serotypes.
Conclusions:
- The WHO methodology significantly underestimates multiple-serotype pneumococcal carriage.
- Sweep serotyping and microarray analysis are more sensitive methods for detecting pneumococcal co-colonization.
- These advanced methods provide a more comprehensive understanding of nasopharyngeal carriage dynamics, essential for public health interventions.
