Chlamydia, Gonorrhea & Syphilis

The most common reportable STI in the United States is also the most silent — most people who have it will never know unless someone screens them.

Chlamydia (Chlamydia trachomatis) is the most commonly reported STI in the US. It is frequently asymptomatic, especially in women, making routine screening essential. Screen all sexually active women under 25 annually and older women with risk factors. Untreated chlamydia causes PID, ectopic pregnancy, and infertility. Treatment: doxycycline 100 mg twice daily for 7 days (preferred) or azithromycin 1 g single dose. Gonorrhea (Neisseria gonorrhoeae) often co-infects with chlamydia. Presents with purulent urethral or cervical discharge, dysuria, and can cause pharyngeal and rectal infections. Treatment: ceftriaxone 500 mg IM single dose (1 g if ≥150 kg). Treat for chlamydia concurrently if chlamydia has not been excluded. Disseminated gonococcal infection causes septic arthritis and dermatitis-arthritis syndrome. Syphilis (Treponema pallidum) progresses through stages. Primary: painless chancre at inoculation site (highly infectious, heals spontaneously in 3–6 weeks). Secondary: diffuse maculopapular rash including palms and soles (pathognomonic distribution), condylomata lata (moist flat wart-like lesions in skin folds), fever, lymphadenopathy. Latent: asymptomatic, detected only by serology. Tertiary: gummas (granulomatous lesions), cardiovascular syphilis (aortitis), neurosyphilis (tabes dorsalis, Argyll Robertson pupils). Diagnosis: RPR or VDRL for screening (quantitative, used to monitor treatment response), FTA-ABS for confirmation (stays positive for life). Treatment: benzathine penicillin G IM — the ONLY acceptable treatment during pregnancy. Jarisch-Herxheimer reaction may occur within 24 hours of treatment. ALL three STIs are reportable diseases. Nurses educate, facilitate partner notification per policy and public health requirements, and support expedited partner therapy where legally authorized and protocolized. Screen for HIV with any new STI diagnosis.

Key Distinctions

Painless chancre is primary syphilis — do not confuse with painful vesicular lesions (herpes). A rash on the palms and soles should trigger syphilis evaluation. Students confuse RPR/VDRL (screening, titers drop with treatment) with FTA-ABS (confirmatory, stays positive for life). Benzathine penicillin G is the ONLY treatment for syphilis in pregnancy — penicillin allergy in a pregnant patient with syphilis requires desensitization, not an alternative antibiotic. Doxycycline is contraindicated in pregnancy — if treating chlamydia in a pregnant patient, use azithromycin.

Clinical Pearl

Palms and soles rash — it's syphilis until proven otherwise. Painless sore — also syphilis. This disease is the great imitator.