A competitive polymerase chain reaction assay for reliable identification of Bordetella pertussis in nasopharyngeal swabs.

In order to optimize the identification of clinically relevant quantities of Bordetella pertussis in nasopharyngeal swabs, an automated assay introducing competitive polymerase chain reaction was established. A 183 base pair DNA fragment from a repetitive region of the Bordetella pertussis genome was amplified in a polymerase chain reaction. An internal control DNA with nine base substitutions was coamplified in the same reaction. The differentiation between the amplified B. pertussis DNA and the internal control was based on hybridisation against two different probes using Enzymun Test DNA Detection (Boehringer Mannheim). Nasopharyngeal swabs from serologically positive patients, clinically diagnosed with whooping cough, serologically negative patients after contact with B. pertussis and a negative group were compared. The advantages of competitive PCR are a reduced risk of false-positive and false-negative results and the possibility to differentiate between the different PCR positive groups.