A prospective social and molecular investigation of gonococcal transmission

Background Gonorrhoea is a common infectious disease, poorly controlled des pite effective treatments. Tracing chains of transmission is difficult, bec ause sexual partners are commonly difficult or impossible to identify. We a ssess the use of gonococcal opa-typing in identifying transmission links no t revealed through interview. Methods Epidemiological data and gonococcal isolates were collected prospec tively from patients at two UK clinics in London and Sheffield. Social and epidemiological data were combined with molecular typing of gonococcal isol ates by a new methodology based on the polymorphisms of the opa gene. Findings In London, interview data and cpa-typing on samples from 215 cases showed a diverse population with few links. In Sheffield, interview data i dentified links between 51 (43%) of 120 cases, whereas cpa-typing suggested a more connected population: 95 (79%) of cases had shared profiles. There was a highly significant correlation between the two distributions with epi demiological clusters appearing as a subset of the cpa clusters. Two large cpa clusters, of 18 and 43 cases, accounted for 50% of local cases of gonor rhoea. Discordance between epidemiological and cpa-typing data was observed at highly connected points in the sexual network. Interpretation Opa-typing is a more powerful tool for epidemiological inves tigation of gonorrhoea transmission than earlier methods. Opa-typing can li nk infections that would otherwise remain unlinked, and may aid interventio ns to control endemic disease.