Determining targets for ceftriaxone resistance detection in Neisseria gonorrhoeae based on genotype–phenotype data: an observational study

BACKGROUND: Increasing antimicrobial resistance to ceftriaxone in Neisseria gonorrhoeae presents a public health crisis. We aimed to identify a target associated with ceftriaxone resistance to support the development of rapid diagnostic tests. METHODS: In this observational study, we included N gonorrhoeae isolates with linked penA (NEIS1753) locus and ceftriaxone minimum inhibitory concentration (MIC) data. We compiled and collated isolate-level data from the international public databases PubMLST and Pathogenwatch, and publications up until March 1, 2025. We determined ceftriaxone resistance using the European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoint of an MIC of 0·250 mg/L or more and the WHO alert value of an MIC of 0·125 mg/L or more. We examined ceftriaxone resistance dynamics, with the sensitivity for susceptibility and resistance based on the constructed penA genotypes calculated. FINDINGS: We compiled 18 689 unique N gonorrhoeae isolates from 71 countries across all WHO regions, collected between 1971 and 2024. Using the EUCAST breakpoint, the overall ceftriaxone resistance rate was 2·4%, with evidence of increasing resistance over time. Analysis of MIC distributions revealed that two alleles, penA 60.001 and penA 237.001, both of the VMTAKGGP genotype, had MIC distributions predominantly above the resistance breakpoint. The VMTAKGGP genotype, defined by the A311V mutation, was associated with a sensitivity of 83·2% (95% CI 79·4-86·6) for detecting ceftriaxone resistance and 99·8% (99·7-99·9) for detecting sensitivity. INTERPRETATION: The A311V mutation is a key marker of ceftriaxone resistance. This target could inform the development of a molecular assay to detect ceftriaxone resistance. FUNDING: Australian Research Council.