Background: Neisseria gonorrhoeae have acquired resistance to many antibiotics and developed decreasing susceptibilities to third generation cephalosporins.
Methods: NG-MAST sequence types and minimum inhibitory concentrations (MICs) were determined by agar dilution for 3422 N. gonorrhoeae isolates submitted to the National Microbiology Laboratory between 2010-2012. Isolates were submitted when the provincial laboratories identify resistance to at least one antibiotic or if the provincial laboratories do not conduct antimicrobial susceptibility testing. MIC interpretations were based on the criteria of the Clinical Laboratory Standards Institute (CLSI) and the World Health Organization (WHO) criteria for decreased susceptibility to cephalosporins.
Results: Among all the isolates tested in Canada during 2010-2012, 22.0% (2103/9366) were resistant to penicillin, 31.3% (2935/9366) to tetracycline, 27.0% (2529/9366) to erythromycin, 31.1% (2916/9366) to ciprofloxacin and 0.8% (76/9366) to azithromycin. Decreased susceptibility to cefixime (MIC ≥ 0.25 mg/L) was identified in 3.3% (98/2970) of isolates in 2010; this increased to 4.2% (140/3360) in 2011 and decreased again to 2.2% (68/3036) in 2012. Decreased susceptibility to ceftriaxone (MIC ≥ 0.125 mg/L) declined from 7.2% (218/2970) of isolates 2010 to 6.2% (208/3360) in 2011 and further to 5.5% (168/3036) in 2012. In 2010, 249 sequence types (STs) were identified: the most common STs were ST1407, ST3150 and ST3158 at 13.3%, 11.3% and 9.0% respectively. In 2011, 238 STs were identified: the most common STs were ST1407, ST3307 and ST3550 at 15.3%, 9.3% and 5.9% respectively. In 2012, 258 STs were identified: the most common STs were ST1407, ST2400 and ST3150 at 11.1%, 7.3% and 6.6% respectively.
Conclusions: Comparing 2010 and 2012 there has been a decline in the proportion of N. gonorrhoeae isolates with decreased susceptibilities to ceftriaxone and cefixime. Continued monitoring of antibiotic susceptibilities of N. gonorrhoeae isolates in Canada is imperative and is associated with modifications of treatment guidelines.