Gonococcal Antimicrobial Surveillance Program of Canada (GASP-Canada): Clinical specimens:

On this page

• Nucleic acid amplification tests
• Provincial and territorial partners
• Methods
• Molecular Sequence Type distribution
• Antimicrobial Resistance Prediction Rates
• NML NAAT Publications

Nucleic acid amplification tests

Nucleic acid amplification tests (NAATs) diagnose approximately 90% of annual gonorrhea cases. The highest incidence of gonorrhea is in northern and remote regions. These areas often face challenges in AMR surveillance. This is due to difficulties in transporting viable N. gonorrhoeae cultures, or because the areas lack the resources to culture gonorrhea. To work around this challenge, the National Microbiology Laboratory (NML) accepts remnant NAAT specimens. The NML then performs multi-antigen sequence typing (NG-MAST)^{Footnote 1} and Single Nucleotide Polymorphism (SNP) detection^{Footnote 2} to predict AMR for gonorrhea treatments.

Figure 1. Number of gonorrhea cases diagnosed in Canada by cultures and NAATs

Provincial and territorial partners

All provinces and territories test all their own GC NAATs and a small portion of those are submitted to NML for further characterization for surveillance purposes. Provinces and territories with little or no N. gonorrhoeae culture AMR surveillance data can submit N. gonorrhoeae NAAT specimens to the NML.

We also provide this testing in areas where treatment-resistant gonorrhoea was detected. AMR predictions and molecular typing are used to monitor the spread of AMR strains of gonorrhea.

Figure 2. N. gonorrhoeae NAAT sample distribution at the NML

Methods

The NML uses NG-MAST on NAAT specimens to identify and characterize strains within each community. We also run AMR predictions for:

• cephalosporins (ceftriaxone and cefixime)
• azithromycin
• ciprofloxacin

We do predictions through a series of single nucleotide polymorphism (SNP) real-time polymerase chain reaction (PCR) assays. These assays predict minimum inhibitory concentration (MIC) ranges for each antimicrobial class. The predictions inform effective treatment options for gonorrhea for each community.

Table 1. Predicted NAAT MICs for cephalosporins, ciprofloxacin, and azithromycin

Antimicrobial	Interpretative Category	NAATs
Cephalosporins	Resistanta	Ceftriaxone	Cefixime
		≥ 0.5 mg/L	≥ 1 mg/L
	Decreased susceptibilityb	0.125 - 0.5 mg/L	0.25 - 1 mg/L
	Intermediate or decreased susceptibilityc	0.032 - ≤ 0.125 mg/L	0.032 - ≤ 0.25 mg/L
		N/A	0.032 - ≤ 0.25 mg/L
	Susceptibled	≤ 0.032 mg/L	≤ 0.032 mg/L
Ciprofloxacin	Resistante	≥ 1 mg/L
	Susceptiblef	< 1 mg/L
Azithromycin	Resistantg	≥ 1 mg/L
	Susceptibleh	< 1 mg/L

Table 1: Notes

NAAT specimens are predicted to have this interpretative category if:

Cephalosporins

• A. penA A311V is present
• B. penA A501P and 2 other SNPs of ponA L421P, mtrR delA, porB G120/A121 or N513Y/G543S are detected
• C. At least three SNPs of ponA L421P, mtrR delA, porB G120/A121 or penA A501/N513Y/G543S are detected
• D. No SNPs of ponA L421P, mtrR delA, porB G120/A121 or penA A501/N513Y/G543S are detected

Ciprofloxacin

• E. Any SNP of gyrA S91 or parC D86/S87/S88 are detected
• F. No SNPs of gyrA S91 or parC D86/S87/S88 are detected

Azithromycin

• G. Any SNP of the mtrR promoter or 23S rRNA A2059G/C2611T are detected
• H. No SNPs of the mtrR promoter or 23S rRNA A2059G/C2611T are detected

Figure 3. NAAT NG-MAST distribution in northern and eastern Canada in Year

Figure 4. Overall Eastern Canada Northern Canada N. gonorrhoeae AMR NAAT Predictions

Notes

Cephalosporin Intermediate to Decreased Susceptibility (Ceph-I-DS) is defined as N. gonorrhoeae strains with an MIC ≥0.032mg/L for ceftriaxone and/or cefixime

Ciprofloxacin resistance (Cip-R) is defined as N. gonorrhoeae strains with an MIC ≥1mg/L

Azithromycin resistance (Azi-R) is defined as N. gonorrhoeae strains with an MIC ≥1mg/L

Recent NML NAAT publications

• Molecular surveillance and prediction of antimicrobial resistance of Neisseria gonorrhoeae in Northern Alberta, Canada, 2015-2018
• Molecular characterization and antimicrobial resistance in Neisseria gonorrhoeae in the Nunavut regions of Inuit Nunangat, Canada, 2018 to 2019
• Multiplex Real-time Polymerase Chain Reaction assays for the prediction of cephalosporins, ciprofloxacin, and azithromycin susceptibility of positive Neisseria gonorrhoeae Nucleic Acid Amplification Test samples

References