Alterations in sample preparation increase sensitivity of PCR assay for diagnosis of chancroid.

A PCR assay for the detection of Haemophilus ducreyi in clinical specimens taken from genital ulcers was developed. Although H. ducreyi, when present in such specimens, could be detected by PCR, the sensitivity of the assay was reduced by the presence of Taq polymerase inhibitors in the specimen. The sensitivity of the PCR assay was improved by the use of detergents in preparing nuclei acids from clinical specimens and by the inclusion of a dialysis step prior to amplification. In addition, sodium phosphate included in the transport medium was found to be an inhibitor of the Taq polymerase.