Abstract: This paper reports a study of the PPNG strains isolated from the city of Nanjing. A total of 300 clinical specimens were collected for screening the PPNG strains. The incidence of PPNG strains was 3.3%. Plasmids of 10 PPNG and 30 non-PPNG strains were extracted and identified by a simple agarose gel electrophoretic method. The molecular weight of plasmid DNA was estimated by companng its migration in gel with DNA preparation of known molecular weights(λ DNA/HindⅢ digest marker). In either PPNG or non-PPNG strains, the most frequent plasmid profile was a combination of 4.2kb, 5.4kb and 39.5kb plasmids. The 5.4kb DNA band was reextracted from agarose gel and digested by restriction endonuclease. The result of the digest pattern suggests that 5.4kb plasmid may be the resistant plasmid encoding for β-lactamase of PPNG in Nanjing.

Key words: Neisseria, gonorrhoeae Drug resistance, Plasmids