Sexually Transmitted Infections
Chapter notes (PDF)PDFA group of infections transmitted by sexual contact, including chlamydia, gonorrhoea, syphilis, HIV, trichomoniasis, and viral hepatitis. UK care emphasises confidential testing, partner notification, and syndrome-based management when empirical therapy is required.
Key Facts
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Key points
- Asymptomatic infection is common - screen high-risk groups and contacts.
- Dual testing for HIV and syphilis serology is routine in sexual health screens.
- Gonorrhoea: treat with ceftriaxone 1 g IM/IV plus azithromycin 1 g PO** (UK BASHH - check current national guidance for resistance patterns).
- Chlamydia: doxycycline 100 mg BD for 7 days first-line; azithromycin 1 g** alternative if pregnancy/doxycycline contraindicated (local policy).
- Partner notification: index case should inform partners from the relevant look-back period; clinics can use accelerated partner therapy where appropriate.
- PrEP (HIV pre-exposure prophylaxis) with tenofovir disoproxil/emtricitabine for eligible individuals - specialist initiation.
Overview
Epidemiology (UK context)
Highest rates are seen in young adults and MSM; inequality and stigma remain barriers to testing.
Syndromes
Urethritis, cervicitis, PID, epididymo-orchitis, proctitis, pharyngeal infection, genital ulceration.
Public health
Confidential GUM/sexual health services provide testing, treatment, and contact tracing.
Clinical Presentation
Presenting complaints
Urethral/vaginal discharge, dysuria, intermenstrual/post-coital bleeding, pelvic pain, testicular pain, anorectal symptoms, ulcers, rash.
Examination
Speculum examination where indicated; testicular examination; lymph nodes; rash (palmar/plantar in secondary syphilis).
Differential Diagnosis
| Syndrome | Important differentials |
|---|---|
| Urethritis | Gonorrhoea, chlamydia, Mycoplasma genitalium, UTI |
| Genital ulcer | Syphilis, HSV, chancroid (rare UK), lymphogranuloma venereum |
| Pelvic pain | PID, ectopic pregnancy, appendicitis, endometriosis |
Diagnosis / Investigation
Tests
- NAAT swabs/urine for chlamydia/gonorrhoea; extragenital sites as indicated.
- Syphilis serology (EIA + confirmatory algorithm).
- HIV Ag/Ab test with consent and pre-test discussion.
- Hepatitis B/C serology depending on risk.
- Microscopy of urethral discharge if available (Gram-negative diplococci).
Management
Empirical syndromic therapy (example - follow BASHH)
- Suspected gonorrhoea: ceftriaxone 1 g IM/IV stat + azithromycin 1 g PO stat.
- Chlamydia: doxycycline 100 mg BD 7 days.
Pelvic inflammatory disease (inpatient severe)
- Ceftriaxone 1 g IV OD + metronidazole 400 mg BD + doxycycline 100 mg BD (14-day course common) - per guideline.
Support
- Condoms, vaccination (HPV, hepatitis A/B where indicated), PrEP referral.
Prognosis
Most bacterial STIs are curable; viral infections (HSV, HIV, hepatitis) require longer-term management. Early treatment reduces complications (infertility, chronic hepatitis).
Other Relevant Information
Confidentiality and safeguarding
Follow GMC and local policies; involve safeguarding leads where minors or vulnerable adults are at risk.