Macrolide Resistance inTreponema pallidumin the United States and Ireland

Abstract

For decades, syphilis infection has been treated with penicillin, and Treponema pallidum has not developed resistance to penicillin. In many countries, the recommended treatment for early syphilis is a single dose of penicillin G benzathine, which maintains bactericidal levels for weeks, killing the slowly metabolizing treponemes. Azithromycin, which has a long tissue half-life and can be administered orally, was found to be effective in the treatment of syphilis in a rabbit model¹ and in small studies in humans.^2-6 Because of its convenience and efficacy, azithromycin is increasingly being used for the treatment of syphilis by clinicians and in disease-control activities in Canada and the United States, although it is not currently recommended by the Centers for Disease Control and Prevention.⁷