Neisseria gonorrhoeae treatment failure to the recommended antibiotic regimen-Québec, Canada, 2015-19

Abstract

Objective: To describe Neisseria gonorrhoeae treatment failure to the recommended antimicrobial regimens (azithromycin, cefixime and ceftriaxone).

Methods: Our study was a longitudinal analysis of treatment failures from an observational open cohort of gonococcal infection cases collected in Québec, Canada (n = 2547) between September 2015 and December 2019. Epidemiological and clinical data were collected using a self-administered questionnaire, direct case interviews and chart reviews. Antimicrobial susceptibility testing was performed using the agar dilution method. To be retained as a treatment failure, cases must have had (i) a laboratory-confirmed gonococcal infection; (ii) a documented treatment; (iii) a positive test of cure (TOC) performed within a defined period and (iv) no sexual contact (vaginal, oral or anal), even protected with a condom, between the beginning of treatment and the positive TOC. A broader definition, including suspected cases, was also examined.

Results: Among 1593 cases where a TOC was performed, 83 had a positive TOC: 11 were retained as treatment failure, and 6 were considered suspected cases (overall = 17/1593; 1.1%). Possible explanations for retained or suspected treatment failure included resistance to the antibiotics used for treatment (n = 1), pharyngeal infection (n = 9, of which 5 had been treated with ceftriaxone and 4 with other regimens); and azithromycin monotherapy (n = 1). Some cases had more than one potential explanation.

Conclusions: Treatment failure occurred in 1.1% of cases of Neisseria gonorrhoeae infection for which a TOC was performed, including some cases of pharyngeal infection treated with ceftriaxone.

Figure 1.

Flow chart of cases included in the Québec sentinel surveillance network, between 1 September 2015, and 31 December 2019, depicting the number of N. gonorrhoeae infection cases, for whom a TOC was performed, among whom the result was positive and were considered as treatment failures according to predefined definitions. The availability of pre-treatment isolates, the number of isolates that were resistant to azithromycin (MIC ≥ 2 mg/L) or resistant (MIC ≥ 0.5 mg/L) or with decreased susceptibility (ceftriaxone MIC ≥ 0.12 mg/L; cefixime MIC ≥ 0.25 mg/L) to 3GC and reasons for exclusion are also mentioned. Abbreviations: NAAT, Nucleic acid amplification test; TOC, test of cure; 3GC, third-generation cephalosporins.