Background The aim of this study is to monitor the trend in antimicrobial resistance in Neisseria gonorrhoeae in Nanjing, China. Gonococcal strains isolated during 2015–2018 were examined for susceptibility to seven antibiotics and compared with results from 2013–14 (Antimicrob Agents Chemother, 2018)

Methods 1173 gonococcal strains were isolated from men with urethritis; n=789 (2015–18), compared with n=384 (2013–14). MICs for seven antibiotics were determined by agar dilution method. Criteria for decreased susceptibility to ceftriaxone (MIC≥0.125 mg/L) and cefixime (MIC≥0.25 mg/L) were defined by WHO. Using CLSI and EUCAST (for azithromycin only) criteria, the following MIC breakpoints were used to ascertain resistance: ≥128 mg/L, spectinomycin; ≥2 mg/L, penicillin and tetracycline and ≥1 mg/L, ciprofloxacin and azithromycin. Resistance determinants were investigated using WGS of two isolates which were resistant to both ceftriaxone and cefixime.

Results The percentage of isolates with decreased susceptibility to ceftriaxone rose from 9.9% in 2013–14 to 23% in 2016 and decreased to 16.7% in 2018 (P=0.01). The percentage of isolates with decreased susceptibility to cefixime rose from 0.3% (2013–14) to 15.7% in 2016 and decreased to 13.7% in 2018 (P<0.0001). 38 isolates displalyed MIC≥0.5 mg/L for cefixime, among them 26.3%(10) belonged to ST5308 and one isolate to ST1407 NG-MAST types. Two isolates that exhibited MIC=1 mg/L for ceftriaxone and MIC=2 mg/L for cefixime were detected in 2017 and 2018, respectively. Each possessed mosaic penA-60.001 gene (the same as FC428 isolated in Japan). Azithromycin resistance decreased from 32.3% (2013–14) to 15.2% (2018) and high-level azithromycin resistance (MIC ≥256 mg/L) decreased from 10.4% (2013–14) to 3.4% (2018) (P<0.001). All 1173 isolates were susceptible to spectinomycin, but resistant to ciprofloxacin. 81.3% isolates were resistant to penicillin and 84.8% to tetracycline.

Conclusion The proportion of N. gonorrhoeae isolates with decreased susceptibility to extended-spectrum cephalosporins increased significantly from 2013 to 2018. Ceftriaxone-resistant strain has emerged in Nanjing, China.

Disclosure No significant relationships.