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Updated: Apr 18, 2026
Capsular Serotyping of Streptococcus pneumoniae by Latex Agglutination
Published on: September 25, 2014
Multi-serotype pneumococcal nasopharyngeal carriage prevalence in vaccine naïve Nepalese children, assessed using
Rama Kandasamy1, Meeru Gurung2, Anushil Thapa2
1Oxford Vaccine Group, Department of Paediatrics, University of Oxford, Oxford, United Kingdom; NIHR Oxford Biomedical Research Centre, Oxford, United Kingdom.
Insights
Most young children in Nepal carry multiple pneumococcal serotypes, highlighting the need for effective vaccines. This study used advanced molecular methods to understand pneumococcal carriage before vaccine introduction.
Area of Science:
- Microbiology
- Epidemiology
- Vaccinology
Background:
- Invasive pneumococcal disease (IPD) is a significant cause of mortality in young children, particularly in low-resource settings.
- Nasopharyngeal carriage studies are crucial for understanding the prevalence of Streptococcus pneumoniae serotypes.
- Data on concurrent carriage of multiple pneumococcal serotypes are limited.
Purpose of the Study:
- To determine the prevalence and serotype distribution of nasopharyngeal pneumococcal carriage in healthy Nepalese children before pneumococcal conjugate vaccine (PCV) introduction.
- To utilize a microarray-based molecular serotyping method to detect multi-serotype carriage.
Main Methods:
- A cross-sectional study was conducted on 600 healthy children (6 weeks to 24 months) in the Kathmandu Valley, Nepal (May-October 2012).
- Nasopharyngeal swabs were cultured, and DNA extracts were analyzed using a molecular serotyping microarray.
- The microarray identified the relative abundance of multiple pneumococcal serotypes.
Main Results:
- Typeable pneumococci were found in 49.5% of samples (297/600).
- Multi-serotype carriage was observed in 20.2% of positive samples (67/297).
- Serotypes targeted by the 13-valent PCV were present in 44.4% of samples with typeable pneumococci.
Conclusions:
- Molecular serotyping reveals a substantial prevalence of pneumococcal co-colonization in young children in Nepal.
- This approach provides a more accurate understanding of vaccine efficacy against carriage and replacement dynamics post-PCV introduction.
- Continued surveillance using this method is recommended to monitor serotype and genotype replacement after PCV implementation.
Abstract:
Invasive pneumococcal disease is one of the major causes of death in young children in resource poor countries. Nasopharyngeal carriage studies provide insight into the local prevalence of circulating pneumococcal serotypes. There are very few data on the concurrent carriage of multiple pneumococcal serotypes. This study aimed to identify the prevalence and serotype distribution of pneumococci carried in the nasopharynx of young healthy Nepalese children prior to the introduction of a pneumococcal conjugate vaccine using a microarray-based molecular serotyping method capable of detecting multi-serotype carriage. We conducted a cross-sectional study of healthy children aged 6 weeks to 24 months from the Kathmandu Valley, Nepal between May and October 2012. Nasopharyngeal swabs were frozen and subsequently plated on selective culture media. DNA extracts of plate sweeps of pneumococcal colonies from these cultures were analysed using a molecular serotyping microarray capable of detecting relative abundance of multiple pneumococcal serotypes. 600 children were enrolled into the study: 199 aged 6 weeks to <6 months, 202 aged 6 months to < 12 months, and 199 aged 12 month to 24 months. Typeable pneumococci were identified in 297/600 (49.5%) of samples with more than one serotype being found in 67/297 (20.2%) of these samples. The serotypes covered by the thirteen-valent pneumococcal conjugate vaccine were identified in 44.4% of samples containing typeable pneumococci. Application of a molecular serotyping approach to identification of multiple pneumococcal carriage demonstrates a substantial prevalence of co-colonisation. Continued surveillance utilising this approach following the introduction of routine use of pneumococcal conjugate vaccinates in infants will provide a more accurate understanding of vaccine efficacy against carriage and a better understanding of the dynamics of subsequent serotype and genotype replacement.
