Chlamydia

The most commonly reported communicable disease in Australia, caused by Chlamydia trachomatis. Those under 30 are at greatest risk. 85–90% of infections are asymptomatic overall.

Simple to test and treat; previous infection gives no immunity against reinfection. May also infect the eye, anus and throat — see Trachoma/Chlamydial Conjunctivitis for ocular disease.

Symptoms and complications

	Symptoms (when present)	Complications
All patients	—	Reactive arthritis (arthralgia ± rash and GI symptoms), conjunctivitis
Women	Vaginal discharge, pelvic pain, dyspareunia, intermenstrual/postcoital bleeding, anorectal symptoms	Pelvic inflammatory disease, infertility, ectopic pregnancy, cervicitis, perihepatitis (Fitz-Hugh-Curtis)
Men	Dysuria, penile urethral discharge, testicular pain, anorectal symptoms	Epididymo-orchitis; prostatitis
Pregnancy	—	Premature rupture of membranes, preterm delivery, low-birthweight infant, ectopic pregnancy

Reactive arthritis is the classic extra-genital complication. Look for arthralgia with a keratodermic rash on the soles, circinate balanitis, and conjunctivitis.

Testing

NAAT (nucleic acid amplification test) is the only recommended test and is highly sensitive. Concurrent gonorrhoea testing should always accompany chlamydia testing.

Sample site by patient:

• Women: self-collected vaginal swab (best if no speculum exam) or clinician-collected endocervical swab (best if being examined anyway) — self-collected vaginal swab is more sensitive than first-pass urine.
• Men: first-pass urine.
• Anorectal swab: any patient with anorectal symptoms, and all men who have sex with men (self-collection or during exam).
• Pharyngeal swab: all men who have sex with men.

Asymptomatic patients can self-collect vaginal, anorectal and throat swabs — encourage this when an examination can’t be performed. See STI Screening for the wider screen this sits inside.

Treatment

Doxycycline is first-line for both uncomplicated and anorectal infection. It has replaced azithromycin as the preferred treatment.

Infection	Recommended	Alternative
Uncomplicated genital or pharyngeal	Doxycycline 100mg PO BD, 7 days	Azithromycin 1g PO stat — consider if adherence to daily dosing is likely to be poor
Anorectal	Doxycycline 100mg PO BD, 7 days if asymptomatic, 21 days if symptomatic	Azithromycin 1g PO stat, repeated at 12–24 hours
Anorectal + gonorrhoea co-infection	Ceftriaxone 500mg IMI stat (in 2mL 1% lignocaine) plus doxycycline as above	—
Pregnancy	Azithromycin 1g PO stat	Seek specialist advice
Allergy to both principal options	Seek specialist advice	—

Start treatment immediately if there’s a high index of suspicion — don’t wait for confirmatory results. If male with urethritis symptoms, start doxycycline while awaiting confirmatory testing.

Sexual contacts are the exception. Immediate treatment isn’t routinely recommended for sexual contacts before their own results are back — offer testing of exposed sites and await results, unless presumptive treatment is indicated (see Contact tracing below). If contacts are treated, use azithromycin only if adherence is likely to be poor or to match the index case’s treatment.

Alongside the antibiotic:

• If the patient has an IUD, leave it in place and treat as recommended.
• Perform a full STI check-up (including HIV and syphilis serology) if not already done.
• Advise no sexual contact for 7 days after treatment starts, or until the course is completed and symptoms have resolved — whichever is later.
• Advise no sex with partners from the last 6 months until they’ve been tested and treated if necessary.
• Notify the state or territory health department; provide the patient with a factsheet.

Contact tracing

Trace all partners back 6 months. The diagnosing doctor is responsible for initiating and documenting this discussion.

• Offer testing of exposed anatomical sites to all sexual contacts.
• Consider presumptive treatment if sexual contact occurred within the last 2 weeks, or where the contact’s circumstances mean later treatment may not happen.
• Patient-delivered partner therapy (the index patient delivers a prescription or treatment to their partner) is an option in some jurisdictions (Victoria, NSW, NT) for heterosexual index patients whose partners are unlikely to seek testing/treatment, or for repeat infections where a partner hasn’t been treated.

Follow-up

Review to confirm treatment adherence and symptom resolution, and confirm contact tracing has occurred (or offer more support with it). Use the visit to discuss condoms, contraception, HIV PrEP/PEP, safe injecting practices, consent, cervical screening, and HAV/HBV/HPV vaccination as indicated.

Test of cure is not routinely recommended, except for pregnancy or anorectal infection treated with azithromycin — in these cases, NAAT test of cure no earlier than 4 weeks after treatment (to avoid a false positive from persistent chlamydial DNA). In pregnancy, retest again in the third trimester.

Reinfection is common — offer retesting at 3 months regardless of test-of-cure status. Consider testing for other STIs if not already done, or repeat after the window period.