Relationship of the interval between infections and the similarity of gonococcal strains in recurrent gonorrhoea.

Paired gonococcal isolates from 38 patients with recurrent episodes of gonorrhoea at varying intervals were examined for similarity by means of gonococcal auxotyping and susceptibility to antibiotics. A different gonococcal strain was the cause of the second infection in 53% of the patients. Longer intervals between infections were significantly associated with greater numbers of dissimilar strains as a cause of the second infection. The same strain was usually found in infections occurring within 60 days of each other whereas different strains were more likely to cause infections occurring more than 60 days apart. The isolates causing the second infection were significantly more susceptible to penicillin.