Medicine chapters
Sexually transmitted infections
The common STIs grouped by how they present (urethral discharge, vaginal discharge, genital ulcer, warts), with the key test and first-line treatment for each, including the stages and serology of syphilis.
- Urethral discharge: gonorrhoea (Gram-negative intracellular diplococci; ceftriaxone) or chlamydia/NGU (often silent; doxycycline); always treat partners and test for syphilis and HIV.
- Genital ulcers: painless firm chancre = primary syphilis; painful grouped vesicles = herpes; painful ragged ulcer with suppurating nodes = chancroid.
- Syphilis is staged primary → secondary (rash on palms and soles, condylomata lata) → latent → tertiary; screen with VDRL/RPR, confirm with TPHA, treat with benzathine penicillin, and watch for the Jarisch–Herxheimer reaction.
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Overview
Sexually transmitted infections (STIs) are infections passed mainly through vaginal, anal or oral sex. Many are silent, especially in women, and untreated infection causes infertility, ectopic pregnancy, chronic pelvic pain, congenital infection and easier spread of HIV.
General rules for every STI:
- Test for other STIs, especially syphilis and HIV (and hepatitis B and C where relevant).
- Notify and treat sexual partners.
- Advise no sex until treatment is finished (usually at least 7 days).
- Promote condoms, and offer hepatitis B and HPV vaccination.
In Pakistan, where laboratory tests are often unavailable, the WHO syndromic approach (treating for the main causes of a syndrome such as urethral discharge or genital ulcer) is used in many services. Check the current national guideline, as recommended drugs change with resistance patterns.
Urethral discharge in men
Gonorrhoea
- Neisseria gonorrhoeae: Gram-negative intracellular diplococcus (kidney-bean pairs inside neutrophils).
- Infects the urethra, cervix, rectum, throat and conjunctiva.
- Incubation 2–14 days, usually 2–5 days in men.
- Men: profuse purulent urethral discharge and dysuria; complication is epididymo-orchitis.
- Women: up to half are asymptomatic; cervicitis, discharge, PID, Bartholin abscess.
- Disseminated gonococcal infection: fever, tenosynovitis, migratory arthritis and a few pustules with necrotic centres on the hands and feet.
- Newborns: purulent conjunctivitis (ophthalmia neonatorum) in the first days of life.
- Diagnosis: Gram stain of urethral pus (high sensitivity in symptomatic men, poor in cervical samples); NAAT is the most sensitive; culture (Thayer–Martin medium) before treatment to check antibiotic resistance.
Gram-negative intracellular diplococci in urethral pus from a man with a purulent discharge is diagnostic of gonorrhoea.
- Treatment: ceftriaxone 1 g IM single dose; ciprofloxacin only if the strain is known to be sensitive. Treat for chlamydia too if it has not been excluded. Test of cure is advised because of rising resistance.
Chlamydia and non-gonococcal urethritis (NGU)
- Chlamydia trachomatis (serovars D–K) is the commonest bacterial STI; no symptoms are noticed by up to 80% of infected women and 50% of infected men.
- Incubation about 1–3 weeks.
- Men: scanty mucoid discharge (worse in the morning), dysuria, epididymo-orchitis, reactive arthritis (especially HLA-B27).
- Women: cervicitis, post-coital or intermenstrual bleeding, PID, tubal infertility, ectopic pregnancy; Fitz-Hugh–Curtis perihepatitis.
- Newborns: conjunctivitis and pneumonia.
- Other causes of NGU: Mycoplasma genitalium, Ureaplasma, Trichomonas, HSV and adenovirus; often no cause is found.
- Diagnosis: NAAT on first-void urine (men) or vulvovaginal swab (women). NGU is shown by 5 or more polymorphs per high-power field on a urethral smear with no diplococci.
- Treatment: doxycycline 100 mg two times a day (7 days). In pregnancy, use azithromycin (1 g then 500 mg daily for 2 days); doxycycline is avoided in pregnancy.
Gonorrhoea and chlamydia often occur together. A patient treated for gonorrhoea alone may keep a chlamydial infection.
Gonococcal versus non-gonococcal urethritis
| Feature | Gonococcal | Non-gonococcal (chlamydia) |
|---|---|---|
| Incubation | Short (2–5 days in men) | Longer (1–3 weeks) |
| Discharge | Profuse, purulent | Scanty, mucoid |
| Gram stain | Intracellular Gram-negative diplococci | Pus cells only |
| Treatment | Ceftriaxone | Doxycycline |
Epididymo-orchitis
- Under 35 years: usually chlamydia or gonorrhoea. Over 35: usually urinary tract organisms. Mumps in non-immune men.
- Exclude testicular torsion (sudden severe pain in a young male) as an emergency.
- STI-related: ceftriaxone single dose plus doxycycline for 14 days.
Vaginal discharge
| Feature | Bacterial vaginosis | Trichomoniasis | Candidiasis |
|---|---|---|---|
| Cause | Overgrowth of Gardnerella, anaerobes, Mobiluncus; loss of lactobacilli | Trichomonas vaginalis (flagellated protozoan) | Candida albicans |
| Sexually transmitted? | No (sexually associated) | Yes | No |
| Itch | Little | Some | Marked vulval itch |
| Discharge | Thin, grey-white, homogeneous, fishy | Profuse, yellow-green, frothy, offensive | Thick, white, curdy ("cottage cheese") |
| Vaginal pH | Over 4.5 | Over 4.5 | Normal (4.5 or less) |
| Other signs | Whiff test positive with 10% KOH; clue cells; no inflammation | Strawberry cervix; motile trichomonads on wet mount | Red, swollen vulva; pseudohyphae on microscopy |
| Treatment | Metronidazole 400 mg two times a day (7 days) (or 2 g once; or vaginal metronidazole/clindamycin) | Metronidazole 400 mg two times a day (7 days); treat partner | Fluconazole 150 mg single oral dose or clotrimazole pessary; topical only in pregnancy |
| Partner treatment | Not needed | Needed | Not needed unless symptomatic |
Bacterial vaginosis is diagnosed when three of four Amsel features are present: thin homogeneous discharge, pH over 4.5, fishy odour with KOH, and clue cells (epithelial cells coated with bacteria). It raises the risk of preterm birth.
Recurrent candidiasis (4 or more episodes a year) needs a check for diabetes and weekly fluconazole for several months.
Pelvic inflammatory disease (PID)
- Infection ascending from the cervix to the uterus, tubes and pelvis; mostly young sexually active women.
- Causes: chlamydia, gonorrhoea, M. genitalium and anaerobes.
- Bilateral lower abdominal pain, deep dyspareunia, abnormal bleeding and discharge, cervical motion and adnexal tenderness.
- Always do a pregnancy test to exclude ectopic pregnancy.
- Treatment (start before results): ceftriaxone 1 g IM once, then doxycycline plus metronidazole for 14 days. Admit if severe, pregnant or a tubo-ovarian abscess is suspected.
- Complications: chronic pelvic pain, ectopic pregnancy and tubal infertility; risk rises with each episode.
Genital ulcers
Comparison of genital ulcers
| Disease | Organism | Incubation | Ulcer | Lymph nodes | Treatment |
|---|---|---|---|---|---|
| Primary syphilis | Treponema pallidum | 9–90 days (mean about 3 weeks) | Single, painless, firm (indurated), clean base | Painless, rubbery, bilateral | Benzathine penicillin |
| Genital herpes | HSV-2 (and HSV-1) | Days | Multiple painful vesicles → shallow ulcers | Tender, bilateral | Aciclovir |
| Chancroid | Haemophilus ducreyi | 4–7 days | Painful, soft, ragged, undermined, dirty base, bleeds easily | Painful, unilateral, suppurating bubo | Azithromycin 1 g or ceftriaxone 250 mg IM once |
| Lymphogranuloma venereum (LGV) | C. trachomatis L1–L3 | 1–4 weeks | Small, painless, transient, often unnoticed | Large tender nodes; groove sign; buboes; proctitis in MSM | Doxycycline for 21 days |
| Donovanosis (granuloma inguinale) | Klebsiella granulomatis | Weeks | Painless, beefy-red, bleeds on touch, enlarges slowly | Pseudobuboes (subcutaneous granulomas) | Azithromycin or doxycycline for at least 3 weeks |
"Do you feel the pain? Ducreyi Does hurt (chancroid); syphilis does not."
- Groove sign in LGV: enlarged inguinal and femoral nodes separated by the inguinal ligament.
- Donovan bodies: intracellular rods in macrophages on Giemsa-stained smears of donovanosis.
- Herpes diagnosis: PCR from the ulcer; Tzanck smear shows multinucleated giant cells.
Genital herpes
- Commonest cause of genital ulcers worldwide; HSV-2 recurs more often than HSV-1.
- Virus becomes latent in the sacral dorsal root ganglia.
- Primary episode: multiple painful ulcers, tender nodes, fever, dysuria (may cause urinary retention), sometimes aseptic meningitis.
- Recurrences: milder, preceded by tingling; asymptomatic shedding spreads infection.
- Treatment: aciclovir 400 mg three times a day (5 days) (or valaciclovir, famciclovir); saline bathing and analgesia. Suppressive aciclovir for frequent recurrences (6 or more a year).
- Pregnancy: a primary episode near term carries the highest risk of neonatal herpes, so caesarean section is advised; suppressive aciclovir from 36 weeks.
Syphilis
The organism
Treponema pallidum, a thin motile spirochaete that cannot be cultured. It is seen by dark-ground microscopy of chancre fluid. Spread is by sexual contact, transplacental (any stage of pregnancy) and blood.
Stages
| Stage | Timing | Features |
|---|---|---|
| Primary | 9–90 days after contact (mean about 21 days) | Painless, indurated chancre with painless regional nodes; heals in 2–6 weeks |
| Secondary | 6–10 weeks after the chancre | Fever, malaise, sore throat; non-itchy, symmetrical, copper-coloured maculopapular rash including palms and soles (in about 75%); generalised lymphadenopathy; condylomata lata (moist wart-like plaques in the anogenital area; highly infectious); mucous patches and snail-track ulcers in the mouth; patchy "moth-eaten" alopecia; hepatitis, nephritis, uveitis |
| Latent | Positive serology, no signs | Early latent (under 2 years; still infectious) and late latent (2 years or more) |
| Tertiary | Years later (in about one-third of untreated) | Gummas (destructive granulomas of skin, bone, liver); cardiovascular (aortitis, aortic regurgitation, ascending aortic aneurysm); neurosyphilis (tabes dorsalis, general paralysis of the insane, meningovascular stroke, Argyll Robertson pupils) |
Early syphilis = primary, secondary and early latent (infectious). Late syphilis = late latent and tertiary.
A non-itchy rash on the palms and soles with generalised lymphadenopathy in a sexually active adult is secondary syphilis.
Condylomata lata (secondary syphilis; flat, moist, teeming with treponemes) are different from condylomata acuminata (genital warts; HPV 6 and 11; cauliflower-like).
Congenital syphilis
- Early (first 2 years): rash, snuffles (nasal discharge), hepatosplenomegaly, periostitis, condylomata lata, stillbirth.
- Late (after 2 years): Hutchinson teeth (notched incisors), saddle nose, sabre tibia, frontal bossing, interstitial keratitis, deafness (Hutchinson triad: teeth, keratitis, deafness).
- Prevent it by screening every pregnant woman and treating with penicillin.
Serology
| Test type | Examples | Use | Key fact |
|---|---|---|---|
| Non-treponemal | VDRL, RPR | Screening; monitoring treatment (titres) | Positive about 3–4 weeks after infection; titre falls with treatment; false positives in pregnancy, SLE, antiphospholipid syndrome, malaria, leprosy, TB, HIV, IV drug use |
| Treponemal | TPHA, TPPA, FTA-ABS, EIA | Confirmation | Highly specific; stay positive for life even after cure, so cannot show re-infection |
Before treatment: VDRL titre 1:64
After treatment: VDRL titre 1:16
Fall = 64 ÷ 16 = 4 → a fourfold fall, showing an adequate response
A positive VDRL with a negative TPHA is a biological false positive: think of SLE or antiphospholipid syndrome.
Treatment
| Stage | First-line | If penicillin allergic |
|---|---|---|
| Early (primary, secondary, early latent) | Single IM dose of benzathine penicillin G 2.4 MU | Doxycycline 100 mg two times a day (14 days) |
| Late latent, cardiovascular, gummatous | Benzathine penicillin G 2.4 MU IM weekly for 3 doses | Doxycycline for 28 days |
| Neurosyphilis | Procaine penicillin IM daily plus probenecid for 14 days (or IV benzylpenicillin) | Doxycycline (higher dose) for 28 days |
| Pregnancy | Penicillin (the only reliable treatment for the fetus) | Doxycycline must not be used |
Jarisch–Herxheimer reaction:
- Fever, chills, headache, myalgia and worsening of the rash a few hours (about 8 hours) after the first dose of treatment.
- Caused by release of cytokines as treponemes die; not an allergy to penicillin.
- Common in secondary syphilis (up to about 90%) and primary syphilis (about 50%).
- Settles within a day; treat with antipyretics; do not stop penicillin. In pregnancy it may trigger early labour.
Follow-up: repeat VDRL/RPR during the first year and expect a fourfold fall in titre. Trace and treat contacts. People with HIV may progress faster and develop neurosyphilis more often.
Anogenital warts
- Caused by HPV types 6 and 11 (low risk; do not become malignant). HPV 16 and 18 cause most cervical and anal cancers but not visible warts.
- Soft, cauliflower-like papules on the penis, vulva, perianal skin; grow in pregnancy and immunosuppression.
- Treatment: podophyllotoxin (soft, non-keratinised warts) or imiquimod (both self-applied; avoid both in pregnancy); cryotherapy or electrocautery for keratinised warts.
- Prevention: HPV vaccine (quadrivalent and nonavalent vaccines cover 6, 11, 16 and 18) given ideally before sexual debut (around 12–13 years).
Other STIs
- Molluscum contagiosum (genital): umbilicated papules on the pubis and thighs; self-limiting; cryotherapy.
- Pubic lice: itching; treat with permethrin or malathion and treat partners (see the scabies and pediculosis chapter).
- Scabies can spread sexually.
- Hepatitis B and HIV: always test; offer hepatitis B vaccination; consider post-exposure prophylaxis after a high-risk exposure.
Expect: Gram stain and treatment of gonorrhoea, chlamydia as the commonest silent bacterial STI and its complications, gonococcal versus non-gonococcal discharge, the painless chancre of syphilis versus painful ulcers of herpes and chancroid, LGV groove sign and donovanosis (Donovan bodies), stages of syphilis (rash on palms and soles, condylomata lata, gummas, tabes, aortitis), VDRL versus TPHA (screening, monitoring, false positives, lifelong positivity), benzathine penicillin and the Jarisch–Herxheimer reaction, bacterial vaginosis versus trichomonas versus candida, PID treatment and complications, and HPV types in warts and cancer.
Quick revision
- Gonorrhoea: intracellular Gram-negative diplococci; profuse pus; ceftriaxone 1 g IM.
- Chlamydia: often silent; mucoid discharge; doxycycline 7 days (azithromycin in pregnancy); PID and infertility.
- Painless ulcer = syphilis; painful vesicles = herpes; painful ragged ulcer + bubo = chancroid.
- LGV: L1–L3, groove sign, doxycycline 21 days. Donovanosis: beefy-red, Donovan bodies.
- Secondary syphilis: palms and soles rash, condylomata lata, snail-track ulcers.
- VDRL/RPR to screen and monitor (fourfold fall); TPHA to confirm, positive for life.
- Benzathine penicillin 2.4 MU IM once for early syphilis; Jarisch–Herxheimer reaction after first dose.
- BV: fishy, pH over 4.5, clue cells, metronidazole. Trichomonas: frothy, strawberry cervix, treat partner. Candida: curdy, itchy, normal pH.
- Warts: HPV 6 and 11; cancer: HPV 16 and 18.
Written by The House Job from standard references (Kumar and Clark's Clinical Medicine; Levinson's Review of Medical Microbiology and Immunology; Gynaecology by Ten Teachers).
FAQ
Which syphilis test is used to follow treatment?
A non-treponemal test such as VDRL or RPR, because its titre falls after successful treatment; a fourfold fall shows an adequate response.
Why can treponemal tests not detect re-infection?
Tests such as TPHA usually stay positive for life after any past infection, even when it has been cured.
Is the Jarisch–Herxheimer reaction a penicillin allergy?
No. It is a short-lived inflammatory response to dying treponemes; penicillin should be continued.
Which genital ulcer is painless and which is painful?
The primary syphilitic chancre is painless and indurated; herpes and chancroid ulcers are painful.
Do male partners of women with bacterial vaginosis need treatment?
No. BV is not regarded as sexually transmitted and treating male partners does not prevent recurrence, unlike trichomoniasis.