Sexually Transmitted Infections (STIs) - A Comprehensive Overview

Classification of STIs by Syndrome

1. Gonorrhea (Neisseria gonorrhoeae)

• Men: Acute urethritis is the most common presentation. Incubation period is 2-7 days. Discharge begins scant and mucoid then becomes profuse and purulent. Dysuria without urinary frequency is typical. Asymptomatic men are a major reservoir of spread.
• Women: Mucopurulent cervicitis, vaginal discharge, dysuria. In the first trimester, ascending infection can cause salpingitis. Disseminated gonococcal infection (arthritis, skin lesions) is more common in pregnant women due to elevated progesterone and increased cervical vascularity.
• Complications: Epididymitis, pelvic inflammatory disease, disseminated gonococcal arthritis, neonatal gonococcal ophthalmia and sepsis.

Gram stain of urethral discharge in gonorrhea: gram-negative intracellular monococci and diplococci within neutrophils. (Harrison's Principles of Internal Medicine, 22e)

• Ceftriaxone 250 mg IM (single dose); always treat for possible co-existent chlamydia.
• Resistance to azithromycin and cephalosporins is an emerging global concern.

2. Chlamydia (Chlamydia trachomatis)

• Men: Urethritis with mild, watery or mucoid discharge (much less intense than gonorrhea) or completely asymptomatic.
• Women: Cervicitis (often asymptomatic), urethritis, pelvic inflammatory disease, postpartum endometritis, preterm labor in pregnancy.
• Neonates of infected mothers: Conjunctivitis and pneumonitis.
• Lymphogranuloma venereum (LGV): Caused by serovars L1-L3 - painless genital ulcer followed by massive inguinal lymphadenopathy (buboes).

• Standard: Azithromycin 1 g orally (single dose) OR doxycycline 100 mg twice daily x 7 days.
• Pregnancy: Azithromycin 1 g (single dose); amoxicillin 500 mg TID x 7 days is an alternative.
• LGV: Doxycycline 100 mg twice daily x 21 days.

3. Syphilis (Treponema pallidum)

Stages of Syphilis

• Painless, indurated ulcer (chancre) at the inoculation site, appearing 10-90 days after exposure.
• The risk of transmission from a single sexual contact is 16-30%.
• Heals spontaneously in 3-6 weeks even without treatment.
• Diagnosed by dark-field microscopy (finding motile spirochetes) or serologic testing.

Chancre of primary syphilis - a painless, indurated, superficial ulceration. (Rosen's Emergency Medicine)

• Appears 2-10 weeks after the chancre resolves when spirochetes spread systemically.
• Characteristic maculopapular rash involving palms and soles (highly pathognomonic), face, trunk, and extremities.
• Also causes: mucous patches, condyloma lata (broad moist papules on genitalia), generalized non-tender lymphadenopathy, "moth-eaten" alopecia.
• Systemic symptoms: low-grade fever, malaise, myalgias, headache.
• These mucocutaneous lesions are highly contagious.

Rash of secondary syphilis involving the palms and soles. (Rosen's Emergency Medicine)

Red to violet raised papules on the palms (A) and soles (B) are characteristic of secondary syphilis. (Creasy & Resnik's Maternal-Fetal Medicine)

• No clinical manifestations. Early latent = within 12 months; late latent = beyond 12 months.
• Patient is not contagious by sexual transmission in late latent stage, but can still transmit transplacentally.

• Gummas: Granulomatous lesions of skin, bone, liver.
• Cardiovascular: Aortitis, aortic aneurysm, aortic insufficiency.
• Neurosyphilis: General paresis, tabes dorsalis, Argyll Robertson pupil (accommodates but doesn't react to light - virtually pathognomonic), meningovascular disease, optic atrophy.

• Primary/secondary: Benzathine penicillin G 2.4 million units IM single dose.
• Late latent: Benzathine penicillin G 2.4 million units IM x 3 weekly doses (7.2 million units total).
• Neurosyphilis: Aqueous crystalline penicillin G IV x 10-14 days.

4. Genital Herpes (HSV-1 and HSV-2)

• Primary episode (no pre-existing immunity): Severe local symptoms - multiple painful vesicles/ulcers on genitalia or perianal area, fever, malaise, myalgia, inguinal lymphadenopathy. Lasts 2-3 weeks.
• Non-primary first episode (partial immunity): Less severe.
• Recurrent episodes: Generally milder, shorter. Often preceded by a prodrome of tingling/burning.
• Asymptomatic shedding: Most transmissions occur during asymptomatic shedding. Most recurrences are not recognized by the patient.

• First episode: Acyclovir 400 mg TID x 7-10 days OR valacyclovir 1 g BID x 7-10 days.
• Recurrence: Valacyclovir 500 mg BID x 3-5 days.
• Suppressive therapy: Valacyclovir 1 g daily (reduces frequency of outbreaks and risk of transmission).

5. Human Papillomavirus (HPV)

• Low-risk types (6, 11, 42, 43, 44): Associated primarily with genital warts (condyloma acuminatum). About 1% of sexually active adults are diagnosed with genital warts annually.
• High-risk types (16, 18, 31, 45, and others): Associated with cervical, anal, oropharyngeal, vulvar, vaginal, and penile cancers. HPV types 16 and 18 account for ~70% of cervical cancers.

• Most HPV infections (majority) are asymptomatic and self-limiting.
• Condyloma acuminata: soft, skin-colored or pink, cauliflower-like growths on the genitalia, perineum, and perianal area.
• High-risk types cause high-grade squamous intraepithelial neoplasia (CIN) and invasive cervical cancer.
• Laryngeal papillomatosis (caused by HPV 6 and 11) - rare but serious in neonates born to infected mothers.

• Genital warts: Patient-applied (podophyllotoxin, imiquimod) or provider-applied (trichloroacetic acid, cryotherapy, surgical removal).
• No antiviral drug eliminates HPV itself; treatment targets lesions.

• Gardasil 9 covers HPV types 6, 11, 16, 18, 31, 33, 45, 52, and 58. Recommended for all persons through age 26; shared decision-making for ages 27-45.

6. Trichomoniasis (Trichomonas vaginalis)

• The annual global incidence exceeds that of chlamydia and gonorrhea combined.
• Symptoms (women): Purulent, frothy yellow-green vaginal discharge; vulvar irritation; elevated vaginal pH. Pathognomonic finding: "strawberry cervix" (colpitis macularis - punctate microhemorrhages of the ectocervix).
• Men: Usually asymptomatic; may cause urethritis.
• Diagnosis: NAAT (most sensitive); wet mount (motile protozoa with flagella visible).
• Treatment: Metronidazole 500 mg twice daily x 7 days (preferred in women) or 2 g single dose; tinidazole 2 g single dose. Treat sexual partners.

7. Bacterial Vaginosis (BV)

• Caused by overgrowth of Gardnerella vaginalis and anaerobes replacing normal Lactobacillus flora.
• Symptoms: Thin, gray-white discharge with fishy odor; no significant inflammation.
• Diagnosis: Clue cells on wet mount, elevated vaginal pH >4.5, positive whiff test (10% KOH), Amsel's criteria.
• Treatment: Metronidazole 500 mg BID x 7 days or metronidazole gel 0.75% intravaginally.

8. Chancroid (Haemophilus ducreyi)

• Painful genital ulcer(s) (in contrast to the painless chancre of syphilis) with ragged, undermined edges.
• Associated with painful inguinal lymphadenopathy (tender buboes) in ~50% of cases.
• Treatment: Azithromycin 1 g orally single dose OR ceftriaxone 250 mg IM single dose.

General Principles of STI Management

1. Syndromic approach: Empiric treatment based on signs/symptoms - used in resource-limited settings.
2. Microbiologic approach: NAAT, culture, and serology - preferred in developed countries; allows resistance monitoring and public health reporting.

• Screened for HIV (early diagnosis has major personal and public health benefits).
• Screened serologically for syphilis.
• Counseled about partner notification and treatment.
• Offered vaccination (hepatitis A, hepatitis B, HPV where applicable).

• Pregnant women: Tetracyclines and quinolones are contraindicated. Treat chlamydia with azithromycin; gonorrhea with ceftriaxone; herpes with acyclovir/valacyclovir (consultation required); syphilis with penicillin.
• Neonates: At risk for conjunctivitis, pneumonitis (chlamydia), ophthalmia and sepsis (gonorrhea), disseminated herpes, and congenital syphilis.

Summary Table