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Background: Dual therapy with ceftriaxone and azithromycin is recommended by CDC for treatment of gonorrhea. Although azithromycin has been effective for the treatment of gonorrhea, azithromycin monotherapy is not recommended because of concerns about rapid emergence of macrolide resistance. In August 2011, a 26 year old man with gonococcal urethritis confirmed by culture in Portland, Oregon reported penicillin allergy and received treatment with azithromycin 2 g orally. Despite abstention from sex, his symptoms persisted and his follow-up culture was again positive for Neisseria gonorrhoeae suggesting possible treatment failure.
Objectives: To describe utilization of molecular typing methods to verify azithromycin treatment failure.
Methods: Antimicrobial susceptibility testing of the pre- and post-treatment isolates was done by agar dilution method according to the Gonococcal Isolate Surveillance Project (GISP) protocol. Molecular typing was done by N. gonorrhoeae multiantigen sequence typing (NG-MAST) and pulsed-field gel electrophoresis (PFGE).
Results: The two isolates had the same NG-MAST sequence type 3709, and were indistinguishable by PFGE with separate NheI and SpeI restriction digest. They had similar susceptibility patterns except that azithromycin MIC increased from 0.5 µg/ml (pre-treatment isolate) to 8 µg/ml (post-treatment isolate).
Conclusions: Persistent urethritis despite sex abstinence between visits, together with identical genetic types, and increase in azithromycin MIC of the post-treatment isolate suggest selection of an azithromycin resistant variant.
Implications for Programs, Policy, and Research: Emergence of a resistant variant in an individual patient during treatment is alarming, and may predict rapid emergence of gonococcal resistance clinically. Clinicians are advised to treat gonorrhea with the CDC recommended antibiotic regimens, with test of cure if azithromycin is used as sole treatment.