A 20-year-old man is evaluated in a sexual health clinic for a 1-week history of anal discomfort and tenesmus. In addition, in the past two days, he noted yellow-white rectal discharge, diarrhea, and abdominal cramping. He denies fever, chills, urethral symptoms, bloody stool, or other symptoms. He engages in insertive and receptive anal intercourse using condoms only occasionally. He is diagnosed with proctocolitis.