Molecular detection and quantification of pertussis and correlation with clinical outcomes in children

Pertussis is an under-recognized serious infection. Conventional cultures are insensitive and of limited utility after antibiotic exposure. We corroborated the utility of real-time polymerase chain reaction (PCR) as a diagnostic tool in pertussis and investigated its role as a prognostic tool by evaluating its benefit in the quantification of pertussis bacterial load. All pertussis-positive PCR tests (n = 104) submitted over 5 years were collected for retrospective study. PCR cycle threshold was compared to quantitative culture in 43. Compared to PCR, the sensitivity of culture was 41%. Our PCR assay reliably quantified bacterial load and was quantitatively reproducible. Higher bacterial load correlated with longer duration of hospitalization (P = 0.0003), and multivariate logistic regression models demonstrated this association to be independent. The study confirmed PCR as a superior diagnostic tool in pertussis. PCR quantification of bacterial load at initial diagnosis predicts later clinical disease severity, suggesting a potential benefit of PCR as a prognostic tool in pertussis.