Prevalence of asymptomatic Bordetella pertussis and Bordetella parapertussis infections among school children in China as determined by pooled real-time PCR: A cross-sectional study

Abstract

Background: Studies have documented that older children and adolescents act as a reservoir of Bordetella pertussis infection for young infants who have not yet completed their primary immunization schedule. Asymptomatic pertussis infection has been reported during outbreaks. This cross-sectional study aimed to investigate whether B. pertussis and Bordetella parapertussis can colonize the nasopharynx of healthy school children, using culture and pooled real-time PCR with targets for insertion sequences IS481 and IS1001. Methods: Nasopharyngeal (NP) swabs were taken from 629 asymptomatic school children aged 7 to 15 y in 4 counties of China during the period July–September 2011. The number of subjects included in each county ranged from 153 to 165. The 4 counties selected are located in the north, south, east, and southwest regions of China. NP swabs were inoculated onto Regan–Lowe agar for isolation of suspected Bordetella organisms. Pooled real-time PCRs were used to detect B. pertussis and B. parapertussis based on the IS481 and IS1001 targets separately. Results: Of the 629 subjects, 2 (0.3%) and 30 (4.8%) were confirmed to be culture-positive and PCR-positive, respectively, for B. pertussis, and 1 (0.2%) and 13 (2.1%) were confirmed to be culture-positive and PCR-positive, respectively, for B. parapertussis. All culture-positive samples were also PCR-positive. Furthermore, positive B. pertussis and B. parapertussis samples were found in all counties. Conclusions: Our results indicate that asymptomatic B. pertussis infections are common in school children in China, and asymptomatic B. parapertussis infections are more prevalent than previously documented.

Keywords::

• Prevalence
• asymptomatic infections
• Bordetella pertussis
• Bordetella parapertussis
• pooled real-time PCR

Acknowledgements

We wish to thank the technicians of the local city and county CDCs, who assisted with the data collection and nasopharyngeal swab collection. We thank the senior technicians at the Shandong and Guangdong CDC laboratories where the 3 strains were isolated.

Declaration of interest: This work was supported by grants from the Chinese Preventive Medicine Association (20100002). The authors declare that they have no conflicts of interest.