Changes in penicillinase-producing Neisseria gonorrhoeae isolated in London.

To investigate changes in the gonococcal population over time, the plasmid content, serotype and auxotype have been determined for strains of penicillinase-producing Neisseria gonorrhoeae (PPNG) isolated from patients attending the Praed Street Clinic for Sexually Transmitted Diseases between 1978 and 1987. Three distinct changes have been identified: (i) in the main plasmid type, from PPNG with the 3.2-Mda plasmid before 1982 to strains with the 4.4-Mda plasmid between 1982 and 1985; (ii) the decline during this time of strains also carrying the 24.5-Mda conjugal plasmid; (iii) the re-emergence of PPNG with the 3.2-Mda plasmid in 1986. The three typing methods used have identified eight clusters of strains which have been prevalent in different years between 1978 and 1987.