Identification of Bordetella pertussis in nasopharyngeal swabs by PCR amplification of a region of the adenylate cyclase gene

Department of Microbiology, University of Glasgow, Glasgow G12 8QQ * Division of Bacteriology, National Institute for Biological Standards and Control, South Mimms, Hertfordshire EN6 3QG Correspondence should be sent to Dr J. G. Coote. Received May 1, 1992 Revision received July 17, 1992. Accepted July 17, 1992 The polymerase chain reaction (PCR) was used to amplify a 522-bp region of the adenylate cyclase toxin ( cyaA ) gene of Bordetella pertussis. As few as 100cfu from a suspension of B. pertussis could be detected by this procedure when the amplified PCR product was detected by ethidium bromide staining of agarose gels. However, simulated clinical specimens, prepared from swabs impregnated with known numbers of B. pertussis cells, only yielded a positive reaction with 10 4 cfu. Hybridisation of a Southern blot of the PCR products from the swab samples with a cya -specific probe gave a positive reaction with as few as 8 cfu, but the hybridisation signal was uniformly weak with fewer than 10 4 cfu. Nevertheless, three of 13 nasopharyngeal swabs, taken from suspected clinically defined cases of whooping cough and stored frozen for up to 18 months, gave a positive PCR reaction. * Present address: Biotechnology Department, ICI Pharmaceuticals, Alderly Park, Cheshire SK10 4TG.