Gonococcal Antimicrobial Surveillance Program — Canada (GASP-Canada): Ceftriaxone and high-level azithromycin resistance:
The Gonococcal Antimicrobial Surveillance Program — Canada (GASP-Canada) monitors antimicrobial resistance (AMR) in gonorrhea across Canada.
- Last updated: 2025-06-09
The Public Health Agency of Canada (PHAC) publishes treatment guidance for gonorrhea infections. Until 2024, the treatment was 250 mg of ceftriaxone or 800 mg of cefixime combined with 1 g of azithromycin. As of late 2024, the recommended treatment is monotherapy of 500 mg of ceftriaxone. Ceftriaxone is the only remaining empiric treatment of gonorrhea.
Ceftriaxone resistant gonorrhea is rare in Canada. Most identified cases are travel related. The Clinical and Laboratory Standards Institute does not have a ceftriaxone-resistant breakpoint. GASP-Canada defines ceftriaxone-resistant as strains with a minimum inhibitory concentration (MIC) of 0.25 µg/mL or greater. This definition was originally used by Tang et. al. in China.
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Cultures with ceftriaxone resistance
Between 2023 and 2024, we identified 11 cases of ceftriaxone-resistant N. gonorrhoeae. This is a significant rise since only 5 cases were reported between 2017 to 2021. The increase in ceftriaxone-resistant strains is a serious threat to effective treatment.
All ceftriaxone-resistant cultures in Canada have the mosaic penicillin-binding protein 2 structure. The structure has a critical mutation (penA A311V) linked to ceftriaxone resistance. Nine of the cultures were classified as having the penA 60.001 allele. In 2024, 1 culture was classified as extensively drug-resistant gonorrhea (XDR-GC). High-level azithromycin resistance is defined as strains with an MIC of 256 µg/mL or greater2. These were the antimicrobials recommended for gonorrhea treatment at the date of collection.
Table 1. N. gonorrhoeae cultures identified in Canada with ceftriaxone MIC ≥0.25 µg/mL
Table 1: Text description
*Abbreviations: CRO = ceftriaxone, CFM = cefixime, AZI = azithromycin, CIP = ciprofloxacin, PEN = penicillin, TET = tetracycline, ERY = erythromycin
The breakpoint for azithromycin resistance MIC≥2.0 µg/mL (3)
The breakpoint for high-level azithromycin resistance MIC≥256 µg/mL (2)
Publications about ceftriaxone resistance in Canada
- Genetic characterization and enhanced surveillance of ceftriaxone-resistant Neisseria gonorrhoeae strain, Alberta, Canada, 2018
- Ceftriaxone-Resistant Neisseria gonorrhoeae, Canada, 2017
References
- Footnote 1
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Tang Y, Liu X, Chen W, Luo X, Zhuang P, Li R, Lin X. Antimicrobial Resistance Profiling and Genome Analysis of the penA 60.001 Neisseria gonorrhoeae Clinical Isolates in China in 2021. J Infect Dis. 2023 Sep 15;228(6):792-799. doi: 10.1093/infdis/jiad258. PMID: 37462623.
- Footnote 2
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Chisholm SA, Dave J, Ison CA. High-level azithromycin resistance occurs in Neisseria gonorrhoeae as a result of a single point mutation in the 23S rRNA genes. Antimicrob Agents Chemother. 2010 Sep;54(9):3812-6. doi: 10.1128/AAC.00309-10. Epub 2010 Jun 28. PMID: 20585125; PMCID: PMC2935028.
- Footnote 3
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World Health Organization, Department of Reproductive Health and Research. Global action plan to control the spread and impact of antimicrobial resistance in Neisseria gonorrhoeae. 2012. [cited 2024 Oct 07].
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