Investigation of ceftriaxone-resistant detected in Scotland, 2018-2024.

Objectives: Describe the clinical, phenotypic and genomic characteristics of ceftriaxone-resistant from Scotland.

Methods: Cases were identified in routine care from 2018 to 2024. Minimum inhibitory concentrations were determined for seven antimicrobial agents. Whole genome sequencing was performed with Illumina and Oxford Nanopore Technology instruments. A phylogeny containing global ceftriaxone-resistant genomes was generated with Parsnp. A collection of ST8780 genomes was also analysed to give further context using reference-based mapping with Snippy.

Results: There were five cases of ceftriaxone-resistant detected. One case (multilocus sequencing typing (MLST) ST1903) clustered within the FC428 lineage in a returning traveller from an Asia-Pacific country. Two cases belonged to the recently described extensively drug-resistant MLST ST16406, a returning traveller from an Asia-Pacific country and a sexual contact within Scotland. The final two cases were a resident of an Asia-Pacific country and a sexual contact within Scotland, both belonged to MLST ST8780. These were distinct from other publicly available ST8780 genomes, suggesting a novel introduction of the mosaic -60.001 allele. All cases were initially treated with ceftriaxone-based regimes, four returned for test of cure and showed clearance of infection.

Conclusions: As ceftriaxone resistance is increasingly identified, multiple public health interventions are required to reduce the impact of resistance on gonorrhoea treatment globally.