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Updated: Oct 6, 2025
Characterization of Inflammatory Responses During Intranasal Colonization with Streptococcus pneumoniae
Published on: January 17, 2014
Comparison of pneumococcal colonization density among healthy children and children with respiratory symptoms using
G Vidanapathirana1, A L S K Angulmaduwa2, T S Munasinghe3
1Faculty of Medicine, University of Peradeniya, Kandy, Sri Lanka.
Insights
Real-time PCR (RT-PCR) offers an alternative for detecting pneumococcal colonization, showing higher overall detection rates than culture. Further evaluation is needed to understand its application in different pediatric groups.
Area of Science:
- Microbiology
- Molecular Diagnostics
- Pediatric Infectious Diseases
Background:
- Nasopharyngeal colonization by Streptococcus pneumoniae is a prerequisite for pneumococcal diseases.
- Real-time PCR (RT-PCR) provides a method for direct identification and quantification of pneumococci in clinical samples.
Purpose of the Study:
- To compare pneumococcal detection rates between culture-based methods and direct RT-PCR.
- To quantify pneumococcal colonization in healthy and hospitalized children using RT-PCR.
Main Methods:
- Analysis of 284 nasopharyngeal swabs from unvaccinated children (2 months to 2 years).
- Comparison of conventional culture with RT-PCR targeting the pneumococcal lytA gene.
- Quantification of pneumococcal DNA using RT-PCR and standard curves.
Main Results:
- RT-PCR detected a higher overall colonization rate (43.7%) compared to culture (41.2%).
- Colonization rates differed between RT-PCR and culture in healthy vs. hospitalized children.
- No statistically significant difference in pneumococcal DNA copy numbers was found between the two cohorts.
Conclusions:
- RT-PCR shows potential for enhanced pneumococcal detection but requires further investigation.
- Interpretation of RT-PCR results, considering potential confounders, needs careful analysis.
- The study highlights the need for further evaluation of RT-PCR for pneumococcal colonization detection.
Background:
Nasopharyngeal colonization is considered a necessary step in the initiation of pneumococcal diseases. Real time PCR (RT-PCR) is an alternative approach for the identification and quantification of pneumococci directly from samples.
Objectives:
To compare pneumococcal detection rates using culture-based method versus RT-PCR direct detection and to quantify pneumococcal colonization in two study cohorts (healthy children and hospitalized children with respiratory symptoms) using quantitation through RT-PCR.
Methodology:
A total of 101 nasopharyngeal swabs (NPS) from healthy children and 183 NPSs from hospitalized children with respiratory symptoms were included in the study. None of the children were vaccinated. All children were between 2 months to 2 years. In parallel to routine culture and identification, a RT-PCR assay targeting the lytA gene was done.
Results:
Considering all 284 samples tested, colonization rate by conventional culture was 41.2% (n = 117) while positive colonization using RT-PCR was 43.7% (n = 124). The colonization rate detected by RT-PCR in the healthy cohort was 33.7% (n = 34) and it was 49.2% (n = 90) in the hospitalized cohort. It was 37.6% (n = 38) and 43.2% (n = 79) for the two cohorts by culture. The mean Cq value for the healthy cohort is 29.61 (SD 2.85) and 28.93 (SD 3.62) for the hospitalized cohort. With the standard curve obtained from amplifying a dilution series of control DNA, the mean amount of genomic DNA copy numbers detected in children with respiratory symptoms was log10 7.49 (SD 1.07) while it was log10 7.30 (SD 0.23) in healthy children and the difference was not statistically significant.
Conclusions:
The overall colonization rate was higher when detected using RT-PCR compared to culture. However, it was lower in the healthy group when detected with RT-PCR compared to culture. Even though there was a higher detection of pneumococcal colonization density in children with respiratory symptoms, this was not significantly higher unlike many previous studies. Therefore, the use of RT-PCR to detect pneumococcal colonization needs further evaluation with careful analysis of interpretation and confounders.
