Molecular Typing of Neisseria gonorrhoeae Isolates by Opa-Typing and Ribotyping in New Delhi, India

Abstract

Control and preventive measures for gonococcal infections are based on precise epidemiological characteristics of N. gonorrhoeae isolates. In the present study the potential utility of opa-typing and ribotyping for molecular epidemiological study of consecutive gonococcal strains was determined. Sixty gonococcal isolates were subjected to ribotyping with two restriction enzymes, AvaII and HincII, and opa-typing with TaqI and HpaII for epidemiological characterization of gonococcal population. Ribotyping with AvaII yielded 6 ribotype patterns while twelve RFLP patterns were observed with HincII. Opa-typing of the 60 isolates revealed a total 54 opa-types, which 48 were unique and 6 formed clusters. Fifty-two opa-types were observed with TaqI-digested PCR product while opa-typing with HpaII demonstrated 54 opa-types. The opa-types from isolates that were epidemiologically unrelated were distinct, whereas those from the sexual contacts were identical. The results showed that opa-typing is highly useful for characterizing gonococcal strains from sexual contacts and has more discriminatory than ribotyping that could differentiate between gonococci of the same ribotype. The technique even with a single restriction enzyme has a high level of discrimination (99.9%) between epidemiologically unrelated isolates. In conclusion, the molecular methods such as opa-typing and ribotyping can be used for epidemiological characterization of gonococcal strains.

Figure 1

Examples of HincII ribotype patterns of consecutive gonococcal isolates: lane M: digoxigenin labeled DNA molecular weight marker III (Roche Diagnostics Corp., Indianapolis, USA); lanes: 1, 7, 12, and 19: ribotype pattern RH6; lanes: 2, 5, 9, 11, 16, and 21: ribotype pattern RH1; lanes: 3, 14, and 5: ribotype pattern RH9; lanes: 4, 10, 18, and 22: ribotype pattern RH3; lanes: 6 and 13: ribotype pattern RH11; lanes: 8, 17, and 20: ribotype pattern RH7.

Figure 2

Dendogram of the cluster analysis of the 60 consecutive gonococcal isolates obtained after opa-typing with HpaII. The relatedness values were calculated as the proportion of unweighted mismatches of fragments between the different patterns. The dendogram was generated by DNASTAR software package.

Figure 3

Examples of different patterns of HpaII opa-types of consecutive gonococcal isolates. Lane M: molecular weight marker (New England Biolabs, USA); lanes 1–18: N. gonorrhoeae isolates; sexual contacts: lanes 13, 14 (HpaII opa-type 13), lanes 15, 16 (HpaII opa-type 14), lanes 17, 18 (HpaII opa-type 15).