Chlamydia
Common bacterial STI caused by *Chlamydia trachomatis*, often asymptomatic but able to cause urethritis, cervicitis, PID, and infertility. First-line treatment in the UK is typically doxycycline for 7 days.
Key Facts
Key points
- NAAT on first-void urine or vulvovaginal swabs (self-taken acceptable).
- First-line: doxycycline 100 mg BD for 7 days.
- Azithromycin 1 g single dose if doxycycline contraindicated (e.g. pregnancy — seek specialist advice; local protocols vary).
- Test of cure 3–5 weeks after treatment if pregnant (NAAT can remain positive due to dead organisms — interpret carefully).
- Lymphogranuloma venereum (LGV) serovars cause proctitis — doxycycline 100 mg BD for 21 days when LGV confirmed/suspected.
Overview
Epidemiology
Most common bacterial STI in young adults; frequently asymptomatic, driving screening programmes.
Pathophysiology
Intracellular organism; chronic inflammation leads to tubal scarring.
Clinical Presentation
Symptoms
Dysuria, mucoid discharge, post-coital bleeding, lower abdominal pain.
Complications
PID, perihepatitis (Fitz-Hugh–Curtis), reactive arthritis.
Differential Diagnosis
| Condition | Notes |
|---|---|
| Gonorrhoea | Often more purulent; co-testing |
| M. genitalium | Persistent symptoms after treatment |
| UTI | Urine dipstick/culture |
Diagnosis / Investigation
Testing
- NAAT; consider M. genitalium if persistent symptoms.
Screen
- HIV/syphilis serology as per sexual health protocol.
Management
Uncomplicated genital infection
- Doxycycline 100 mg orally BD for 7 days.
Epididymo-orchitis (chlamydia suspected)
- Doxycycline 100 mg BD 10–14 days ± ceftriaxone 500 mg–1 g IM if gonorrhoea not excluded.
Partner notification
- Treat partners from prior 2 weeks (extend per guideline).
Prognosis
Excellent with correct antibiotics; delayed treatment increases infertility risk.
Other Relevant Information
Azithromycin resistance
Emerging resistance in M. genitalium — avoid inappropriate macrolide use.