While PCR is the most common method used for detecting Bordetella pertussis in the US, most laboratories use insertion sequence 481 (IS481), which is not specific for B. pertussis; therefore, the relative contribution of other Bordetella species is not understood. The objectives of this study were to evaluate the proportion of other Bordetella spp. misidentified as B. pertussis during a period of increased pertussis incidence, determine the level of agreement in Bordetella species detection between US commercial laboratories and CDC, and assess the relative diagnostic sensitivity of CDC’s PCR assay when using a different PCR master mix. Specimens collected between May 2012-2013 were tested at two US commercial laboratories for B. pertussis and B. parapertussis detection. Every fifth specimen positive for IS481 and/or IS1001 with Ct values ≤35 was sent to CDC for PCR testing that identifies Bordetella species. Specimens with CDC PCR indeterminate or negative results were tested using an alternate PCR master mix. Of 755 specimens, there was agreement in species identification for 83.4% (n=630). Of those with different identifications (n=125), 79.2% (n=99) were identified as indeterminate B. pertussis at CDC. Overall, 0.66% (n=5) of the specimens were identified as B. holmesii or B. bronchiseptica at CDC. Of 115 specimens with indeterminate or negative results, 46.1% (n=53) were B. pertussis positive when tested by an alternate master mix, suggesting possible increase in assay sensitivity. This study demonstrates good agreement between the two US commercial laboratories and CDC and little misidentification of Bordetella species during the 2012 US epidemic.
Journal:J Clin Microbiol. 2015