Description

Enrolled criteria:

1. PLWH aged 20 years or more
2. PLWH with early syphilis (i.e. primary, secondary, or early latent syphilis), confirmed by a positive rapid plasma reagin (RPR) titer with a reactive Treponema pallidum particle agglutination (TPPA) assay.
3. PLWH has provided informed consent *A participant with repeated syphilis can be repeated enrolled after signing an informed consent if the previous episode of early syphilis was successfully treated with achieving at least a 4-fold decrease in RPR titers and 48-week follow-up is completed.

Exclusion criteria:

1. PLWH with RPR titers of less than 4
2. Exposure to antibiotics with activity against T. pallidum, such as penicillins, third-generation cephems, doxycycline, or macrolides, within the preceding 4 weeks
3. A known or suspected infection other than syphilis requiring additional treatment with an antimicrobial active against T. pallidum
4. A history of intolerance to penicillin, ceftriaxone, or doxycycline
5. Pregnancy

Primary outcome:

Serologic response at month 6 (defined as either a 4-fold or greater decline in RPR titer compared to baseline or being RPR-nonreactive)

Secondary outcomes:

1. Microbiologic response of syphilis (defined as T. pallidum PCR Ct value >38) at week 4
2. Microbiologic response of bacterial STIs (defined as negative PCR results) at week 4
3. Serologic response at months 3 and 12
4. Safety of study treatment recorded by using a diary (all adverse events will be coded and graded according to Common Terminology Criteria for Adverse Events [CTCAE] v4.0.)
5. Adherence evaluation (the noting of tablet intake in the diary for the 7 days of the treatment period)