Laboratory diagnosis of gonococcal infection by genetic transformation

Abstract

The transformation test for the detection of infection by Neisseria gonorrhoeae has been examined using pro gonococci as recipients and DNA preparations from 912 clinical isolates and from 240 direct swab specimens as donors. The reliability of the method was checked with DNA from clinical isolates; 82% of the N. meningitidis from throat swab specimens were capable of transforming the gonococcal recipients, but after identification of the meningococcus by the aminopeptidase profile, the transformation test was then 99.5% positive for the gonococcus with virtually no false-positives. The only other organism to give a positive reaction was N. lactamica, which occurred once in 912 specimens. When applied directly to swab specimens, the reliability of the test was reduced, but this may have been related to variability of the specimen itself. However, 7 of 15 specimens which were microscopically suspected to be gonococci but unculturable were positive; also, 9 out of 38 unculturable specimens that were not even suspected to be gonococci were positive. Hence the test was able to identify the presence of gonococci that were unculturable. The aminopeptidase activities were not sensitive enough to be detected in the direct swab specimens, and neither cys nor leu auxotrophs were suitable as recipients to give a differentiation between N. gonorrhoeae and N. meningitidis. Evidence was obtained which would support the proposition that the transfer of genetic material between N. gonorrhoeae and N. meningitidis may occur.