Objective: The routine clinical laboratory detection of Bordetella pertussis is through culture, which can require 5 to 7 days for the bacteria to grow. Using a polymerase chain reaction (PCR) assay can shorten this detection time while increasing the sensitivity of detection with similar specificity. This study compared culture with TaqMan PCR for detection of B pertussis in clinical specimens and the turnaround time for each assay during the pertussis season.
Materials and methods: Nasopharyngeal swabs in Regan-Lowe transport media were collected from 1556 persons who had symptoms of whooping cough or who had had contact with infected persons; the swabs were submitted for B pertussis detection during the pertussis season. A single nasopharyngeal swab from each patient was submitted for both culture and TaqMan PCR detection. Upon receipt of the specimens, the swabs were inoculated onto Regan-Lowe agar for culture and incubated for up to 7 days. The same swab was processed for PCR detection using TaqMan PCR assay. A second nested PCR was used on positive specimens for resolution purposes. The TaqMan PCR assay was performed 3 to 5 days a week, whereas the culture was performed 6 days a week. All specimens were processed on the same day or earliest possible working day for TaqMan or culture, and specimens queued for resolution by nested PCR were batched.
Results: There were a total of 275 PCR positives and 28 culture positives. After resolution with the second nested PCR, the sensitivity, specificity, positive predictive value, and negative predictive value were 100%, 97.4%, 87.6%, and 100% for TaqMan PCR and 11.6%, 100%, 100%, and 85.7% for culture. The average turnaround time for positive culture was 5.1 days, and the average turnaround time for PCR was 2.3 days.
Conclusion: The TaqMan PCR assay has superior sensitivity and shorter turnaround time over culture because it can be finished within one working day. Furthermore, the same swab can be used for culture of the bacteria for antibiotic susceptibility testing. The early detection of pertussis using TaqMan PCR assay allows early intervention on the spread of the disease and the ability to culture the bacteria from the same swab, thereby eliminating the need for a second swab and allowing for detection of antibiotic resistance.