Emergence and Characterization of Neisseria gonorrhoeae Isolates With Decreased Susceptibilities to Ceftriaxone and Cefixime in Canada: 2001–2010

Background: Globally, Neisseria gonorrhoeae antimicrobial resistance has been increasing, and in particular, reports of isolates with reduced susceptibility to third-generation cephalosporins have surfaced. We examined the phenotypic and genetic characteristics of 155 N. gonorrhoeae isolates with decreased susceptibilities to third-generation cephalosporins isolated in Canada between 2001 and mid-2010. Methods: Minimum inhibitory concentrations (MICs) were determined by agar dilution on N. gonorrhoeae isolates, and those displaying elevated MICs to cefixime (MIC = 0.25 ?μg/mL and 0.5 μg/mL) and ceftriaxone (MIC = 0.125 μg/mL and 0.25 μg/mL) were examined using N. gonorrhoeae multiantigen sequence typing (NG-MAST) and sequencing of resistance determinants associated with decreased cephalosporin susceptibilities (penA, mtrR, ponA, porBlb (penB alteration). Results: Between 2001 and 2010, there has been a shift in the modal MICs from 0.016 to 0.125 μg/mL for cefixime and from 0.016 to 0.063 μg/mL for ceftriaxone. Thirty-seven different sequence types (STs) were identified among the isolates using N. gonorrhoeae multiantigen sequence typing; ST3158, ST225, and ST1407 were most prevalent at 25.9%, 19.4%, and 14.8%, respectively. The penA mosaic was present in 60% of the isolates, with the most common penA mosaic types XXXII and X identified at 51.0% and 7.7%, respectively, whereas the nonmosaic penA type XII was identified in 36.8% of the isolates. Conclusions: In Canada, N. gonorrhoeae isolates with decreased susceptibilities to third-generation cephalosporins have increased over the years. The alterations in penA, mtrR, and porB1b (penB alteration)