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Updated: Jun 13, 2026
Experimental Human Pneumococcal Carriage
Published on: February 15, 2013
Marked difference between adults and children in Bordetella pertussis DNA load in nasopharyngeal swabs
Y Nakamura1, K Kamachi, H Toyoizumi-Ajisaka
1Department of Bacteriology II, National Institute of Infectious Diseases, Tokyo, Japan. kamachi@nih.go.jp
Insights
Whooping cough (pertussis) shows lower Bordetella pertussis DNA loads in adults compared to children. This age-related difference in bacterial load explains milder adult symptoms and negative cultures in pertussis.
Area of Science:
- Microbiology
- Pediatrics
- Infectious Diseases
Background:
- Bordetella pertussis causes whooping cough, presenting as severe respiratory illness in children and mild cough in adults.
- Clinical symptom variability between pediatric and adult pertussis patients necessitates understanding underlyingpathogen dynamics.
Purpose of the Study:
- To investigate the correlation between Bordetella pertussis bacterial load and patient age.
- To elucidate the reasons for differential clinical manifestations of pertussis in children versus adults.
Main Methods:
- Quantitative IS481 real-time PCR was employed to measure B. pertussis DNA loads in nasopharyngeal swabs (NPS).
- Samples were collected from 19 adults and 40 children (including 14 infants) pre-diagnosed using loop-mediated isothermal amplification.
- Bacterial loads were quantified using a standard curve with B. pertussis Tohama cells.
Main Results:
- Significantly lower B. pertussis DNA loads were detected in adult NPS (mean Ct 34.9) compared to child NPS (mean Ct 27.1) (p <0.001).
- Adults exhibited low DNA loads throughout disease stages, with estimated bacterial counts of ~320 cells.
- Infants had the highest bacterial loads (estimated ~1.1 x 10⁶ cells), followed by older children (estimated ~2.1 x 10⁴ cells).
Conclusions:
- Nasopharyngeal B. pertussis load is strongly correlated with patient age.
- Adult pertussis is characterized by diminished nasopharyngeal bacterial burden, correlating with milder symptoms and reduced culture positivity.
Abstract:
Bordetella pertussis is the aetiologic agent of whooping cough, a common cause of severe respiratory illness in children and prolonged mild cough in adults. To understand some of the reasons for differences in clinical symptoms between adults and children, we measured B. pertussis DNA loads in nasopharyngeal swabs (NPS) from 19 adults and 40 children (including 14 infants) by quantitative IS481 real-time PCR. All cases had been pre-diagnosed with the B. pertussis-specific loop-mediated isothermal amplification method. The mean PCR threshold cycles for adult and child NPS were 34.9 and 27.1, respectively, indicating a significantly lower B. pertussis DNA load in adults than in children (p <0.001). Moreover, adults had very low DNA loads during both early and later stages of the disease. When corresponding bacterial loads in NPS were calculated for B. pertussis Tohama cells using a standard curve, the mean number of bacterial cells taken with a rayon-tipped swab from an adult, older child and infant was estimated to be 320 (95% CI 120-910), 2.1 × 10⁴(95% CI 5.3 × 10³ to 8.3 × 10⁴) and 1.1 × 10⁶ cells (95% CI 1.2 × 10⁵ to 8.9 × 10⁶), respectively. This indicates that the B. pertussis load in NPS is closely correlated with patient age. Our observations suggest that adult pertussis is characterized by a lower bacterial load in the nasopharynx, resulting in milder symptoms and negative cultures.
