This will be a randomized, open-label, non-comparative, adaptive pilot trial to evaluate the efficacy of two linezolid oral dosing schemes (600mg orally, twice a day, for five or ten days) compared to the current recommendation for the treatment of syphilis, benzathine penicillin G (single dose of 2.4 million units) in participants with and without HIV infection. In total, 60 participants will be enrolled across 2 clinical sites in Peru. Participants will participate in follow-ups to monitor clinical outcomes and serological response (RPR titer) at 1 month, 3 months, and 6 months. The investigators will also test linezolid against several types of syphilis strains in the lab to evaluate the microbicidal activity of linezolid in treating early syphilis. Study findings may identify an efficacious alternative syphilis treatment to penicillin that is effective for people living with HIV. Study findings may also help address the crisis of penicillin shortages, difficulty in administration, and offer options for those with penicillin allergy.
The two specific aims are: AIM 1: To evaluate the efficacy of linezolid compared to benzathine penicillin G in the treatment of syphilis. AIM 2: Evaluate the susceptibility of Treponema pallidum historical and novel strains to linezolid.