Chlamydia
Also known as: Chlamydial Genitourinary Infection
Chlamydia trachomatis (serovars D through K for genitourinary disease) is an obligate intracellular bacterium and the most commonly diagnosed bacterial STI in most high income settings.
It disproportionately affects those under 25, and untreated infection in women carries significant risk of ascending infection and subsequent tubal factor infertility.
The majority of infections, particularly in women, are asymptomatic, which underlies the importance of opportunistic and targeted screening programs.
When symptomatic: in women, mucopurulent cervical discharge, postcoital or intermenstrual bleeding, and dysuria (see Cervicitis entry); in men, urethral discharge and dysuria.
Untreated infection can ascend to cause pelvic inflammatory disease in women (see that entry) and epididymo-orchitis in men.
Rectal and pharyngeal infection are frequently asymptomatic and require site-specific testing based on sexual history.
Reactive arthritis (formerly Reiter syndrome) is a recognized post-infectious complication.
- NAAT testing is the diagnostic method of choice given superior sensitivity, from a first-void urine sample (men), vulvovaginal swab (self-taken or clinician-taken, equally sensitive to endocervical swab in women), or site-specific rectal/pharyngeal swab based on sexual history
- Opportunistic screening is recommended for sexually active individuals under 25 in many national programs, and for anyone with a new partner, multiple partners, or symptoms suggestive of infection
- Co-testing for gonorrhea, syphilis, and HIV should be offered given shared transmission routes
- Doxycycline 100 mg PO bd for 7 days is now first line for uncomplicated urogenital, rectal, and pharyngeal infection, having superseded single-dose azithromycin as first choice given superior efficacy, particularly for rectal infection where azithromycin cure rates are notably lower
- Azithromycin 1 g PO single dose, followed by 500 mg PO od for 2 further days (total 2 g over 3 days) is an alternative where doxycycline is contraindicated or adherence to a 7 day course is a significant concern
- In pregnancy: doxycycline is contraindicated; azithromycin 1 g PO single dose (then 500 mg od for 2 days per some protocols) is first line, with amoxicillin 500 mg PO tds for 7 days as an alternative
- Test of cure is not routinely required except in pregnancy, rectal infection treated with azithromycin, or where symptoms persist, given in these situations delayed clearance or treatment failure is more likely; if performed, should be delayed at least 5 weeks post-treatment to avoid false positives from residual non-viable organism DNA
- Sexual partners in the preceding 6 months (or the most recent partner if longer than 6 months since last intercourse) should be tested and treated, with abstinence advised until both partners have completed treatment and, ideally, 7 days have passed
- Neonatal exposure: chlamydia acquired during vaginal delivery from an infected mother can cause neonatal conjunctivitis (typically day 5 to 14) or pneumonia (typically 4 to 12 weeks); treated with erythromycin per neonatal dosing, not topical treatment alone
Referral: sexual health services for partner notification and full STI screening; gynecology if complications (PID, tubal factor infertility) develop.
