The emergence of penicillinase-producing Neisseria gonorrhoeae strains carrying the 4.9 kb (Toronto) plasmid in Denmark and of a novel large plasmid in two nonpenicillinase-producing Neisseria gonorrhoeae strains.

This study comprised plasmid analysis and antimicrobial susceptibility testing of 712 out of a total of 730 penicillinase-producing Neisseria gonorrhoeae (PPNG) and 744 random non-PPNG strains isolated in Denmark between 1985 and 1990. The rate of patients with PPNG infections rose from 1% to 2% during 1985-1987 to 6.9% in 1989, and then decreased to 4.8% in 1990. A decrease in cases of gonorrhea from 9,798 to 1,990 was seen during the same period. Strains harboring the 4.9 kb (Toronto) plasmid first appeared in 1987; in 1988-1990, 65% to 78% of strains from patients with PPNG infections acquired in Denmark contained this plasmid. The majority of these strains seemed to belong to a single clone. Tetracycline-resistant PPNG strains (MIC greater than 32 mg/L) first appeared in Denmark in 1989, and tetracycline-resistant non-PPNG strains carrying a 40 kb plasmid (tetM?) first appeared in 1990. A novel 41-42 kb plasmid appeared in one strain in 1987 and another in 1988. The minimum inhibitory concentration (MIC) of tetracycline for these two strains was 4 mg/l. The significance of this plasmid is yet unknown.