National Surveillance of Antimicrobial Susceptibilities of Neisseria gonorrhoeae in Canada - Annual Summary 2016

Executive Summary

This report compares laboratory surveillance data for Neisseria gonorrhoeae isolates submitted by provincial microbiology laboratories to the National Microbiology Laboratory (NML) from 2012 - 2016.

The Canadian reported rate of gonorrhea is on the rise and has more than doubled from 21.8 per 100,000 in 2001 to 55.4 per 100,000 in 2015. Gonorrhea is the second most commonly reported bacterial sexually transmitted infection in Canada with 19,845 cases reported in 2015.

Over time, N. gonorrhoeae has acquired resistance to many antibiotics such as penicillin, tetracycline, erythromycin and ciprofloxacin. Antimicrobial resistance in N. gonorrhoeae is a serious threat to effective treatment of gonococcal infections.

In 2016, a total of 4,538 N. gonorrhoeae isolates were cultured and tested in public health laboratories across Canada; 3,092 of these were submitted to the NML for antimicrobial susceptibility testing. The total number of isolates cultured in all provinces was used as the denominator to calculate resistance proportion.

The following WHO breakpoints were used throughout this report: decreased susceptibility to cefixime at MIC≥0.25 mg/L and decreased susceptibility to ceftriaxone at MIC≥0.125 mg/L (WHO, 2012).

Isolates with decreased susceptibility to cefixime have declined from 1.9% (80/4,190) in 2015 to 0.3% (14/4,538) in 2016.

Isolates with decreased susceptibility to ceftriaxone declined from 3.5% (146/4,190) in 2015 to 1.8% (80/4,538) in 2016.

The proportion of azithromycin resistant (MIC≥2 mg/L) N. gonorrhoeae isolates increased steadily from 0.9% (26/3,036) in 2012 to 4.7% (198/4,190) in 2015. In 2016, 7.2% (326/4,538) of isolates tested were resistant to azithromycin.

In 2016, 47.1% (2,136/4,538) of isolates were resistant to ciprofloxacin; 31.7% (1,439/4,538) of the isolates were resistant to erythromycin; 17.4% (791/4,538) were resistant to penicillin; and 53.3% (2,419/4,538) were resistant to tetracycline.

All N. gonorrhoeae isolates submitted to the NML were also analyzed by molecular genotyping using the N. gonorrhoeae multi-antigen sequence type (NG-MAST) method. In 2016, 490 different sequence types (STs) were identified among the 3,092 isolates tested and the most common sequence types were ST-5985 (11.9%), ST-12302 (10.5%) and ST-10451 (5.7%).

ST-12302 increased from 4.3% of all isolates in 2015 to 10.5% in 2016; the isolates were primarily identified in central Canada. ST-12302 isolates were resistant to multiple drugs with over 70% also resistant to azithromycin.

ST-10451 is highly related to ST-1407, an internationally identified clone that has been described as a superbug, with high-level resistance to cephalosporins. Most ST-10451 isolates identified in 2016 were resistant to multiple drugs and over 5% of these were resistant to azithromycin.

In 2016, only 1 isolate with resistance to azithromycin and decreased susceptibility to cefixime and ceftriaxone was detected in Canada. It was identified as ST-2318.

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