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Sexually Transmitted Infections

Ashley Zeoli



  • Cause: gram-negative coccus Neisseria gonorrhoeae
  • Gonorrhea causes a spectrum of disease including urethritis, cervicitis, epididymitis, proctitis, pharyngeal infections, conjunctivitis, PID, and disseminated gonococcal infection


  • Microbial diagnosis is required to diagnose gonorrhea, rather than clinical diagnosis alone
  • Test of choice: NAAT of the first-catch urine in men; NAAT of vaginal swab in women
    • Also perform co-testing for chlamydia
  • NAAT of pharyngeal or rectal swab should also be performed in patients with reported symptoms and recent sexual exposure. Note this is also routine testing in patients on PREP.
  • Routine screening should be offered to sexually active patients, as many are asymptomatic


  • Ceftriaxone is the only current antibiotic that meets the strict treatment efficacy goals with single-dose therapy. CTX also has a low rate of drug resistance, which is becoming an increasing issue in the treatment of gonorrhea.

    • High dose IM ceftriaxone (<150kg 500mg IM; >150mg 1g IM)
      • Same for pharyngitis or conjunctivitis
    • CTX allergies: Azithromycin (2g PO x1) + Gentamicin (240mg IM x1) or Gemifloxacin
  • Treatment of chlamydia must also be accompanied with gonorrhea treatment when it has not been excluded with molecular testing.

    • Doxycycline 100mg BID for 7 days
  • Patients who have persistent symptoms despite treatment should be suspected of having resistant gonorrhea. Test with culture and antimicrobial susceptibility testing (with or without NAAT).

  • Patients with recurrent symptoms after period of resolution should be re-evaluated for gonorrhea and other STIs



  • Cause: gram negative bacteria Chlamydia trachomatis

  • Most individuals are asymptomatic though causes a wide array of infections: urethritis, cervicitis -> PID, conjunctivitis, perihepatitis (Fitz-Hugh-Curtis syndrome), pneumonia, proctitis, epididymitis, reactive arthritis, pharyngitis, lymphogranuloma venereum (LGV), endemic trachoma

  • Differential diagnosis: Neisseria gonorrhoeae, Trichomonas vaginalis, Mycoplasma genitalium


  • Test of choice: NAAT of vaginal swab in females (first catch urine also adequate); NAAT of first catch urine in males.

  • NAATs can detect both LGV and non-LGV chlamydia trachomatis, but cannot distinguish between them

  • Any patient with signs and symptoms concerning for chlamydia should be tested. Testing should also routinely be offered to sexually active individuals since most patients are asymptomatic. Note this is also routine testing in patients on PREP.


  • Doxycycline 100mg BID x 7 days is the preferred treatment in non-pregnant patients (azithromycin is NOT preferred) Alternative treatment options (for allergies/severe contraindications): azithromycin (1g PO x 1), levofloxacin (500mg PO daily x7 days), and ofloxacin (300mg BID PO x7 days) Patients with recent potential or confirmed exposure within the last 1-2 weeks should be treated empirically

  • Patients with persistent symptoms, confirmed infection, and who already underwent appropriate treatment, likely have a re-infection, rather than treatment failure. Test again.

  • Patients with recurrent symptoms after resolution should be re-tested for chlamydia with a NAAT and other STIs (gonorrhea, BV, etc).

  • Empiric therapy for gonorrhea should be given to patients unless NAAT is negative



  • Caused by the spirochete, Treponema pallidum, which is visualized by dark field microscopy

  • High rate of HIV co-infection among MSM with syphilis (~42%)

  • Transmitted by direct contact with an infectious lesion during sex. Infection can occur anywhere inoculation occurs (i.e. contact with infected secretions can result in a lesion on any tissue site)

  • Can readily cross the placenta -> fetal infection

  • Patients can present with a variety of symptoms, depending on their place in the disease course


  • Test all patients with signs and symptoms, as well as patients who are at increased risk for acquiring infection (patients with sexual partner with early syphilis, MSM, people living with HIV, high risk sexual behaviors, and history of commercial sex work or incarceration)

  • HIV testing should be offered to all patients who test positive

  • Pregnant patients should be screened for syphilis

  • There are two types of serologic tests: treponemal-specific tests (FTA-ABS, MHA-TP, TPPA, TP-EIA, CIA) and nontreponemal tests (RPR, VDRL, TRUST). Either can be used as initial screening, but confirmatory testing with the other is needed due to false positives.

    • Treponemal specific are usually used as confirmatory tests when nontreponemal tests are reactive. They are reported as reactive or non-reactive. Once positive, usually positive for life.
    • Nontreponemal quantifies amount of antibody present and can be used to detect titers to assess for treatment. Titers should decline after a patient has been treated. A rise in titers in a previously treated patient should be concerning for new infection.
      • Requires a humoral response, so can be false negatives if immunocompromised
      • False positives: autoimmune diseases, pregnancy, other infections
  • At VUMC, a positive treponemal IgG reflexes to a RPR titer.

  • Neurosyphilis can occur at any time after infection. All newly diagnosed patients with syphilis should have a full neurologic exam and if any abnormalities should have an LP sent for CSF-VDRL.

  • Any patients with syphilis and vision changes should undergo ophthalmology evaluation.

+ Treponemal

- Treponemal
+ Non-treponemal Diagnostic of syphilis (completely new, or potentially re-infected) Likely false positive
- Non-treponemal Likely history of successfully treated syphilis Likely not syphilis, or false negative (due to prozone\* effect)
\*Prozone effect: when there is an overabundance of antibodies and they interfere with clumping/formation of antigen-antibody complex so agglutination cannot be visualized


  • To assess treatment efficacy, we want to see a fourfold decrease in titer after treatment
Symptoms Treatment Treatment Alternatives
Primary Painless chancre at inoculation site with regional lymphadenopathy PCN G benzathine 2.4 million units IM x1

Doxycycline 100mg PO BID x 14 days


Ceftriaxone 1-2g daily IM or IV x 10-14 days


Tetracycline 500mg PO QID x 14 days


Amoxicillin 3g BID and probenecid 500mg BID x 14 days

Secondary Systemic illness with rash (palms, soles), fever, malaise, alopecia, hepatitis, mucous patches, condyloma, pharyngitis
Early Latent Infected, but no symptoms. Occurs within one year of initial infection.
Tertiary Symptomatic late syphilis (CV system, gummatous disease) PCN G benzathine 2.4 million units IM weekly x3 weeks

Doxycycline 100mg PO BID x 4 weeks


Ceftriaxone 2g daily IM or IV x 10-14 days

Late Latent

Infected, but no symptoms. Occurs >1 year after initial infection.

Assume late latent with date of infection unknown



Can occur at any time.

Early: asymptomatic or symptomatic meningitis, vision loss, hearing loss

Late: brain and spinal cord manifestations (dementia, tabes dorsalis)

Treat ocular syphilis like neurosyphilis

Aqueous PCN G 3-4 million units IV q4h x 10-14 days


PCN G procaine 2.4 million units IM daily and probenecid 500mg PO QID x 10-14 days

If PCN allergic, desensitize

Ceftriaxone 2g daily IM or IV x 10-14 days

Last update: 2022-06-21 21:56:27