Widespread resistance of Neisseria gonorrhoeae to penicillin, tetracycline, and fluoroquinolones has challenged effective treatment and control; recent international case reports of cefixime, ceftriaxone, and azithromycin resistance suggest that the remaining treatment options are now additionally threatened. To explore trends in antimicrobial susceptibility of N. gonorrhoeae, we reviewed provincial laboratory data from British Columbia, 2006 to 2011.
Susceptibility testing was performed for all N. gonorrhoeae isolates detected in-house or forwarded to the reference laboratory. Resistance or intermediate resistance (nonsusceptibility) was defined by standard breakpoints for penicillin, tetracycline, ciprofloxacin, and spectinomycin. Elevated minimum inhibitory concentrations (MICs) at serial dilutions of 0.064 μg/mL or greater were explored for cefixime/ceftriaxone and 0.5 μg/mL or greater for azithromycin. Nonsusceptibility/elevated MIC was compared by year, site of infection, sex, and age.
A total of 1837 isolates representing 22% of all reported gonorrhea cases were analyzed. Nonsusceptibility to penicillin was established at baseline. Nonsusceptibility to tetracycline and ciprofloxacin increased over the study period, reaching 96% and 36%, respectively, in 2011. Sixteen isolates (1%) had a cefixime MIC of 0.25 μg/mL (none ≥0.5), none had a ceftriaxone MIC of 0.25 μg/mL or greater, and 15 (1%) had an azithromycin MIC of 2.0 μg/mL or greater. Elevated MIC of these agents showed an increasing trend over time. Nonsusceptibility and elevated MIC were consistently highest at the rectal and pharyngeal sites and higher in isolates from males, including when stratified to the pharyngeal site.
Increases in elevated MIC of cefixime/ceftriaxone/azithromycin were superimposed on a background of established resistance to penicillin, tetracycline, and ciprofloxacin and may signal impending gonococcal resistance to first-line treatments. Ongoing surveillance will inform timely shifts in treatment recommendations.
We observed temporal increases, between 2006 and 2011, in the percentage of continuously sampled Neisseria gonorrhoeae exhibiting elevated minimum inhibitory concentration of cephalosporins and azithromycin at or just below the nonsusceptible threshold.
From the *British Columbia Centre for Disease Control, Vancouver, Canada; †University of British Columbia, Vancouver, Canada; ‡British Columbia Public Health Microbiology and Reference Laboratory, Vancouver, Canada §Public Health Agency of Canada, Ottawa, Canada; and ¶National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, Canada
The authors gratefully acknowledge Claudia Rank for preliminary analyses of British Columbia (BC) Neisseria gonorrhoeae susceptibility data, Rob MacDougall for data extraction, and Theodora Consolacion for data preparation.
Supported by BC Public Health Microbiology and Reference Laboratory, BC Centre for Disease Control (in kind).
Conflicts of interest: None declared.
Correspondence: Richard T. Lester, MD, BC Centre for Disease Control, 655 West 12th Ave, Vancouver, British Columbia, Canada V5Z 4R4. E-mail: firstname.lastname@example.org.
Received for publication April 26, 2012, and accepted July 20, 2012.