# In Vitro Activity of Zoliflodacin Against Neisseria gonorrhoeae Isolates from Shanghai, China (2020–2023)

## TL;DR

Zoliflodacin shows strong effectiveness against drug-resistant gonorrhea bacteria in Shanghai, offering a promising new treatment option.

## Contribution

Demonstrates zoliflodacin's potent in vitro activity against multidrug-resistant Neisseria gonorrhoeae isolates in Shanghai.

## Key findings

- Zoliflodacin had low MIC values (≤0.004 to 0.25 mg/L) against 876 N. gonorrhoeae isolates.
- It remained effective against isolates resistant to ceftriaxone, azithromycin, and other antibiotics.
- Genomic analysis found no mutations linked to zoliflodacin resistance in most isolates.

## Abstract

Background/Objectives: The escalating threat of drug-resistant Neisseria gonorrhoeae underscores the urgent need for novel therapeutic agents. Zoliflodacin, a first-in-class spiropyrimidinetrione antibiotic that targets bacterial DNA gyrase and topoisomerase IV, represents a promising candidate for gonorrhea treatment. Methods: From 2020 to 2023, a total of 876 urogenital N. gonorrhoeae isolates were collected from 35 hospitals across Shanghai, China. In vitro susceptibilities to zoliflodacin and six conventional antibiotics (penicillin, tetracycline, ciprofloxacin, azithromycin, ceftriaxone, and spectinomycin) were determined using the agar dilution method. Whole-genome sequencing was conducted to identify sequence types (STs) and amino-acid substitutions in GyrA, GyrB, ParC, ParE, and MtrR. Results: Zoliflodacin exhibited potent in vitro activity, with minimum inhibitory concentrations (MICs) ranging from ≤0.004 to 0.25 mg/L (MIC50 = 0.06 mg/L; MIC90 = 0.125 mg/L), all below the breakpoint (0.5 mg/L). Notably, zoliflodacin maintained high activity against isolates resistant to ceftriaxone, azithromycin, ciprofloxacin, penicillin, and tetracycline. Although all isolates were susceptible to zoliflodacin, elevated MIC values were observed in ST7363 and ST8123 compared with other clones. Genomic analysis identified no substitutions associated with increased zoliflodacin MICs, and most GyrB sequences, the key gene associated with zoliflodacin resistance, remained intact. Conclusions: These findings demonstrate that zoliflodacin possesses robust activity against circulating multidrug-resistant N. gonorrhoeae lineages in Shanghai and support its potential clinical use for the treatment of gonorrhea. Continued genomic and phenotypic surveillance is warranted to preserve the long-term efficacy of this novel agent.