Drug resistance surveillance and plasmid genotyping of Neisseria gonorrhoeae isolated from Zhuhai

Abstract

Objective To monitor the in vitro antimicrobial susceptibilityof clinical isolates of Neisseria gonorrhoeae from Zhuhai area during 2015-2016, and understand epidemic features of plasmid mediated TEM-1 and tetM genes. Methods The agar dilution method was used to determine the minimum inhibitory concentrations (MICs) of Neisseria gonorrhoeae strains to 7 antibiotics (penicillin G, tetracycline, ciprofloxacin, cefixime, ceftriaxone, spectinomycin and azithromycin) . Penicillinase (β-lactamase) -producing N. gonerrhoeae (PPNG) was analyzed by the paper acidometric method. A multi-PCR was used to amplify TEM-1 and tetM gene fragments, and the drug resistant plasmid profiles were analyzed by electrophoresis. Results There were 26 PPNG strains (27.96%) and 24 tetracycline resistant N. gonorrhoeae (TRNG) strains (25.81%) detected out of 93 strains. The resistance rates of 93 strains to penicillin G, tetracycline, ciprofloxacin and azithromycin were 40.86%, 75.27%, 100.00% and 7.53%, respectively. The rate of low susceptibility to penicillin G was 51.61%. No ceftriaxone, spectinomycin or cefixime resistant strains were detected. However, the rate of low susceptibility to ceftriaxone was 30.11%. Totally, 26 PPNG strains were identified from all the isolates, of which 15 strains (57.69%) carried the Asian type plasmids, 11 strains (42.31%) carried the Africa type plasmids, but none carried the Toronto or Rio type plasmids. There were 24 TRNG strains (25.81%) in these isolates, of which 23 strains (95.83%) harbored the Dutch variant of the tetM gene and 1 strain (4.17%) harbored the American variant. Conclusions Clinical isolates of Neisseria gonorrhoeae from Zhuhai have relatively high drug resistance to penicillin G, tetracycline and ciprofloxacin, but have high susceptibility to ceftriaxone and spectinomycin. Therefore, ceftriaxone and spectinomycin can be used as the first-line agents in gonorrhea treatment. In this region, most PPNG strains carry the Asian type plasmids, followed by the Africa type plasmids. The Dutch variant of the tetM gene is the most common variant among TRNG strains, while the American variant is the occasional form. Key words: Neisseria gonorrhoeae; Drug resistance; TEM-1; tetM