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. The shortcomings of phenotypic typing methods has led to development of molecular genetic methods. Epidemiological analysis of N. gonorrhoeae isolates by genotypic methods has not been carried out in India so far. Therefore, in the present study the potential utility of opa-typing and ribotyping for molecular epidemiological study of gonococcal strains was determined. Sixty gonococcal isolates were collected from among 62 males with urethritis, 22 females with endocervicitis, and 10 sexual contacts of these patients from January, 2006 to June, 2007 in New Delhi. The isolates were subjected to ribotyping (with 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 of 54 opa-types, from which 48 were unique and 6 formed clusters. Of the 48 isolates with unique opa-types, none were known to be from sexual contacts. 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. The results of both methods indicate that gonococcal infection among the patients studied was not derived from common core groups. In conclusion, the molecular methods such as opa-typing and ribotyping can be used for epidemiological characterization of gonococcal strains. Copyright © 2009 Pejvak Khaki et al.