Prevalence of and risk factors for quinolone-resistant Neisseria gonorrhoeae infection in Ontario

Background

Quinolone-resistant Neisseria gonorrhoeae has swiftly emerged in Canada. We sought to determine its prevalence in the province of Ontario and to investigate risk factors for quinolone-resistant N. gonorrhoeae infection in a Canadian setting.

Methods

We used records from the Public Health Laboratory of the Ontario Agency for Health Protection and Promotion in Toronto, Ontario, and the National Microbiology Laboratory in Winnipeg, Manitoba, to generate epidemic curves for N. gonorrhoeae infection. We extracted limited demographic data from 2006 quinolone-resistant N. gonorrhoeae isolates and from a random sample of quinolone-susceptible isolates. We also extracted minimum inhibitory concentrations for commonly tested antibiotics.

Results

Between 2002 and 2006, the number of N. gonorrhoeae infections detected by culture decreased by 26% and the number of cases detected by nucleic acid amplification testing increased 6-fold. The proportion of N. gonorrhoeae isolates with resistance to quinolones increased from 4% to 28% over the same period. Analysis of 695 quinolone-resistant N. gonorrhoeae isolates and 688 quinolone-susceptible control isolates from 2006 showed a higher proportion of men (odds ratio [OR] 3.1, 95% confidence interval [CI] 2.3–4.1) and patients over 30 years of age (OR 3.1, 95% CI 2.4–3.8) in the quinolone-resistant group. The proportion of men who have sex with men appeared to be relatively similar in both groups (OR 1.4, 95% CI 1.1–1.8). Quinolone-resistant strains were more resistant to penicillin (p < 0.001), tetracycline (p < 0.001) and erythromycin (p < 0.001). All isolates were susceptible to cefixime, ceftriaxone, azithromycin and spectinomycin.

Interpretation

During 2006 in Ontario, 28% of N. gonorrhoeae isolates were resistant to quinolones. Infections in heterosexual men appear to have contributed significantly to the quinolone resistance rate. Medical practitioners should be aware of the widespread prevalence of quinolone-resistant N. gonorrhoeae and avoid quinolone use for empiric therapy.After declining for a number of years, Neisseria gonorrhoeae infections are once more on the rise in Canada. Between 1997 and 2007, reported incidence of the disease more than doubled, from 15 to 35 cases per 100 000.¹ To address the emergence of quinolone-resistant N. gonorrhoeae strains, the empiric treatment regimens for N. gonorrhoeae infection were recently revised in the 2006 Canadian Guidelines on Sexually Transmitted Infections.^2,3 Quinolones are no longer recommended for empiric therapy for N. gonorrhoeae infection.³In Canada, quinolone resistance in N. gonorrhoeae isolates increased from an estimated 2% in 2001 to 16% in 2005.⁴ Demographic risk factors for quinolone-resistant N. gonorrhoeae infection have not been studied. American studies have associated quinolone-resistant N. gonorrhoeae infection with men who have sex with men,^5,6 antibiotic use,^5,7 age above 35 years,⁵ HIV infection⁵ and travel to Asia.⁶ Public health data from the provinces of Quebec⁸ and Alberta² have also suggested an association between quinolone-resistant infection and men who have sex with men. In this study we generated epidemic curves for N. gonorrhoeae and quinolone-resistant N. gonorrhoeae infection in the province of Ontario. We also investigated demographic risk factors for quinolone-resistant N. gonorrhoeae infection.