Concordance between Neisseria gonorrhoeae genotypes recovered from known sexual contacts

Neisseria gonorrhoeae multiantigen sequence typing (NG-MAST) is a highly discriminatory molecular typing procedure that provides precise and unambiguous strain characterization. Since molecular typing can complement contact tracing for reconstructing gonorrhea sexual networks, the concordance between the NG-MAST genotypes of pairs of N. gonorrhoeae isolates from recent sexual contacts was examined. Among 72 pairs of gonococci from recent sexual contacts, the genotypes of each pair were concordant in 65 cases (90.3%). In two further pairs, the isolates from sexual contacts differed by only a single nonsynonymous substitution in the porin gene, and in both of these pairs, the isolates were the same by opa typing. The other five nonconcordant pairs of isolates were clearly different strains. opa typing data were available for 51 of the pairs of isolates from sexual contacts, and concordant opa types were obtained in 38 cases (74.5%). NG-MAST should therefore be better than opa typing at identifying recent sexual contacts and has the important advantage over opa typing of being a more precise method of strain characterization.