A 51-year-old man is diagnosed with primary syphilis based on a non-painful genital ulcer and positive syphilis serologic tests. He reports one new male and one female sex partner in the past year. Both sex partners are contacted and instructed to come to the clinic for evaluation. The female sex partner is seen in the clinic and she reports sexual contact with the 51-year-old man about 3 weeks ago. She has no symptoms and says she had negative testing for bacterial sexually transmitted infections (STIs) and HIV about 6 months ago. She does not have any antibiotic allergies.