Evaluation of a DNA probe of plasmid origin for the detection of Neisseria gonorrhoeae in cultures and clinical specimens.

This study evaluates a cryptic plasmid-derived DNA probe in a dot-blot hybridization assay of 4-h duration, using both known bacterial isolates and clinical specimens. The probe, consisting of a 237 bp segment of the plasmid-encoded gene cppB, sequences of which are also found in the chromosome, was labelled with digoxigenin-11-dUTP. The sensitivity of the probe was approximately 25 pg of DNA or 500 cfu of Neisseria gonorrhoeae. A total of 170 reference strains of Neisseria gonorrhoeae and other related bacteria were tested for reactivity with the probe. All N. gonorrhoeae strains, including three plasmid-free strains, hybridized with the probe. Among the heterologous bacterial cultures, only one strain of N. cinerea reacted with the probe when the cell concentration was 5 x 10(6) cfu. The probe was also evaluated in a clinical study. A total of 201 patients visiting the STD clinic at the University Hospital, University of Seville, participated in the study. The sensitivity of the assay was 95% while the specificity was 98%. Positive and negative predictive values were 97% and 98%, respectively. It appears that the plasmid-derived probe used in this study could serve as a useful tool in the rapid and specific detection of Neisseria gonorrhoeae in clinical specimens.