Background Neisseria gonorrhoeae have acquired resistance to many antimicrobials including third generation cephalosporins and azithromycin, the current co-therapy recommended by the Canadian STI guidelines for gonorrhea treatment. Resistance to azithromycin and molecular sequence types were determined for N. gonorrhoeae circulating in Canada.
Methods From 2014–2017, N. gonorrhoeae isolates and data collected by Canadian provincial public health laboratories was submitted to the National Microbiology Laboratory (N=12,776) for N. gonorrhoeae multi-antigen sequence typing (NG-MAST) and azithromycin MIC determination (resistance MIC≥2.0 mg/L) by agar dilution, as described by the Clinical Laboratory Standards Institute.
Results Azithromycin resistance was identified in 3.3% (127/3,809), 4.7% (198/4,190), 7.2% (326/4,538) and 11.6% (616/5,290) of N. gonorrhoeae in 2014, 2015, 2016 and 2017, respectively, a significant increase between 2014–2017 (p<0.001). MICs ranged from 2-≥256 mg/L. The most common sequence types identified in the azithromycin resistant isolates include: 2014; ST10451 (n=40), ST10567 (n=38) and ST11765 (n=10); 2015; ST12302 (n=110), ST10451 (n=34) and ST9047 (n=23); 2016: ST12302 (n=240), ST15750 (n=27) and ST10451 (n=10); 2017; ST12302 (n=375), ST14698 (n=119) and ST15750 (n=17). ST12302 was newly recognized in 2015 and identified in only two provinces, Quebec and Ontario, but spread to Alberta (n=10) and British Columbia (n=16) in 2017. ST12302 is associated with low-level azithromycin resistance (MIC=2 mg/L). ST10451 emerged in 2014 in Quebec, Ontario and Alberta and was also identified in 2015–2017. ST10451 is related to ST1407 (differing by 1 bp) which is an internationally-recognized epidemic strain, harboring cephalosporin resistance.
Conclusion Azithromycin resistance in N. gonorrhoeae is established and spreading in Canada, increasing significantly between 2014 and 2017. This exceeds the 5% level at which the WHO states an antimicrobial should be reviewed as an appropriate treatment. Continued surveillance of antimicrobial susceptibilities and sequence types of N. gonorrhoeae is necessary to identify clusters, inform treatment guidelines and mitigate the impact of resistant gonorrhea.
Disclosure No significant relationships.
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