Analysis of antibiotic resistance of Neisseria gonorrhoeae in Guangzhou

Objective To investigate the antimicrobial susceptibility and the trend of resistance of Neisseria gonorrhoeae strains isolated in Guangzhou in 2005. Methods Agar dilution method was used to determine the minimum inhibitory concentrations (MICs) of penicillin G, tetracycline, ciprofloxacin, ceftriaxone and spectinomycin against the N. gonorrhoeae isolates. High level plasmid-mediated tetracycline resistant N. gonorrhoeae (TRNG) were interpreted according to the criteria (MIC ≥ 16 mg/L) used in the project of surveillance of gonococcal susceptibility in WHO Western Pacific Region. Penicillinase-producing N. gonorrhoeae was dteetcted by disk acidometric method. Plasmid DNA was obtained by alkaline lysis method. Results A total of 104 strains of N. gonorrhoeae were studied. Fourteen (13.5%) strains were plasmid mediated penicillin-resistant isolates (PRNG), and 15 (14.4%) were tetracycline-resistant (TRNG). The prevalence of ciprofloxacin-resistant isolates was 76.9% (80/104), while none appeared to be resistant to ceftriaxone or spectinomycin. MIC50 and MIC90 values of penicillin, tetracycline and ciprofloxacin were 8 mg/L and 32 mg/L, 2 mg/L and 32 mg/L, 4 mg/L and 32 mg/L, respectively. Their MIC50 and MIC90 values were significantly higher than the criteria for resistance. Conclusions High susceptibility of N. gonorrhoeae to ceftriaxone and spectinomycin suggests that these two antibiotics should be used as the first-line treatment for gonorrhoea. The N. gonorrhoeae isolates in our study are relatively resistant to penicillin, tetracycline and ciprofloxacin.