Comparison of sequencing of the por gene and typing of the opa gene for discrimination of Neisseria gonorrhoeae strains from sexual contacts

Typing of gonococcal strains is a valuable tool for the biological confirma tion of sexual contacts. We have developed a typing method based on DNA seq uencing of two overlapping por gene fragments generated by a heminested PCR . We compared sequencing of the por gene (POR sequencing) and typing of the opa gene (OPA typing) for the characterization of strains from 17 sexual p artnerships. Both methods were highly discriminatory. A different genotype was detected in 15 of the 17 epidemiologically unconnected couples by FOR s equencing and in 16 of the 17 couples by OPA typing with restriction enzyme HpaII, Within partnerships, identical genotypes were obtained from 16 of t he 17 known sex contacts by FOR sequencing and from 15 of the 17 by OPA typ ing. Compared to OPA typing, which relies on interpretation of bands in a g el, DNA sequence data offer the advantage of being objective and portable. As costs for sequencing decline, the method should become affordable for mo st laboratory personnel who wish to type gonococcal strains.