1. Definition and clinical relevance
Chlamydia trachomatis and Neisseria gonorrhoeae are the two most common bacterial sexually transmitted infections (STIs) in Australia. Both are notifiable conditions and are frequently co-detected, which is why treatment is often directed at both organisms simultaneously in syndromic presentations.
Chlamydia:
- Obligate intracellular bacterium
- Most commonly notified STI in young Australians
- Frequently asymptomatic, particularly in women
- Drives ongoing transmission and complications: pelvic inflammatory disease (PID) and tubal infertility
Gonorrhoea:
- Caused by Gram-negative diplococcus N. gonorrhoeae
- Typically causes more purulent discharge
- Rising antimicrobial resistance shapes current treatment regimens
Sites of infection:
- Urethra, cervix, rectum, pharynx
Clinical manifestations:
- Urethritis
- Cervicitis/mucopurulent cervicitis
- PID
- Epididymo-orchitis
- Disseminated infection
Why it matters:
- Untreated infection has major reproductive consequences
- Early detection and treatment (including of sexual partners) is a public health priority
- Substantial proportion of infections are asymptomatic
- Opportunistic and population-based screening is central to control, especially in young people and men who have sex with men
Common clinical syndromes:
- Penile urethritis
- Vaginal discharge
- PID
- Anorectal symptoms
2. Key values, thresholds and decision rules
The Queensland Primary Clinical Care Manual (PCCM) provides a practical syndromic treatment guide used where results are not immediately available. Ideally the clinician watches the patient take single-dose medicines.
| Symptom / syndrome | Treat for | Treat with |
|---|---|---|
| Vaginal discharge; penile discharge/dysuria | Gonorrhoea, chlamydia and trichomonas | Ceftriaxone 500 mg AND Azithromycin 1 g AND Metronidazole 2 g |
| Anorectal discharge/pain suggestive of STI | Gonorrhoea and chlamydia (+ HSV if pain) | Ceftriaxone 500 mg AND Doxycycline 100 mg bd for 21 days (+ treat HSV if pain) |
Key drug notes (grounded):
| Drug | Form/route | Dose | Notes |
|---|---|---|---|
| Ceftriaxone | IM into gluteal muscle | 500 mg | Contraindicated in severe/immediate allergy to cephalosporins or penicillins; be aware of cross-reactivity between penicillins, cephalosporins and carbapenems |
| Azithromycin | Oral tablet 500 mg | 1 g stat (2 g if pharyngeal gonorrhoea) | For M. genitalium, 1 g stat then further 1 g stat on day 8 |
| Doxycycline | Oral | 100 mg bd for 7 days (urethritis); 100 mg bd for 21 days (anorectal) | Preferred first-line for chlamydia/NGU |
| Metronidazole | Oral | 2 g | Covers trichomonas in syndromic treatment |
Decision rules to remember:
- In symptomatic penile urethritis, given community prevalence of chlamydia, treat empirically with doxycycline 100 mg twice daily for 7 days while awaiting results.
- A single stat dose of azithromycin is no longer first-line for chlamydia/urethritis, because its use drives Mycoplasma genitalium resistance.
- M. genitalium is often resistant to azithromycin and doxycycline; azithromycin fails to eradicate about 10% of infections.
- A negative screen does not exclude chlamydia or gonorrhoea in a patient with a clinical picture consistent with PID.
3. Approach: presentation and differential
History
- Ask about discharge (colour, amount), dysuria, and duration of symptoms. Gonococcal urethritis typically causes a purulent discharge; chlamydial urethritis produces a milky or yellow discharge, and may present only as spots on underpants or dampness under the foreskin.
- Take a focused sexual history and risk assessment: number of partners, new partner, partners in the last few months, sexual practices (vaginal, anal, oral), and whether the patient is a man who has sex with men (MSM).
- Ask about symptoms of complications: pelvic pain, deep dyspareunia, abnormal bleeding (PID); scrotal pain/swelling (epididymo-orchitis); anorectal pain or discharge.
- Screen for features that raise STI risk in women with discharge: age under 21, unmarried/not cohabiting, more than one partner in the last 3 months, or a new partner.
Examination
- Men: inspect for urethral discharge or an inflamed meatus; the urethra can be "milked" to reveal discharge. Dried discharge on the penis also supports urethritis.
- Women: speculum examination to assess for mucopurulent cervicitis, cervical ectropion, polyps, foreign body; bimanual examination for adnexal mass and cervical motion tenderness (suggesting PID).
- Scrotum: always exclude testicular torsion in a painful, swollen scrotum. Acute torsion typically causes severe pain, worse on walking, not relieved by supporting the testicle.
Differential
- Penile urethritis: N. gonorrhoeae, C. trachomatis, M. genitalium, HSV, adenovirus, Trichomonas vaginalis. Ureaplasma urealyticum is considered normal urethral flora. In up to half of cases no pathogen is identified.
- Vaginal discharge: the most common cause in reproductive-age women is normal physiological discharge. Non-STI causes include candidiasis, bacterial vaginosis (associated with sexual activity but not classed an STI), Group B streptococcal vaginitis. Non-infectious causes include hormonal contraception, cervical ectropion/polyps, malignancy, retained tampon, dermatitis, allergic reaction and lichen planus.
- Pelvic pain: consider PID, but also non-infective gynaecological causes if chronic and no organism found.
4. Investigations
Bedside
- Where available, a Gram stain from the cervix or urethral discharge can suggest N. gonorrhoeae. Urethral microscopy showing more than 5 polymorphonuclear leucocytes per high-power field supports urethritis (non-gonococcal if no organisms seen).
- A wet preparation from the vagina helps detect Trichomonas.
Bloods
For a full STI/BBV screen (as per the PCCM approach), consider serology for:
- HIV antibody/antigen (if not known positive)
- Syphilis serology
- Hepatitis B (HBsAg, Anti-HBs, Anti-HBc if not vaccinated or chronically infected)
- Hepatitis C antibody (if risk factors and no prior history)
Microbiology / NAAT
- Nucleic acid amplification testing (NAAT/PCR) is the mainstay for detecting chlamydia and gonorrhoea, and is used on swabs and urine in asymptomatic patients.
- Men: first-pass urine (FPU) for chlamydia and gonorrhoea NAAT. If discharge is present, take an additional urethral swab for microscopy and culture (culture is important for gonococcal antimicrobial resistance testing).
- Women: self-collected vaginal swab for chlamydia and gonorrhoea PCR, plus trichomonas PCR.
- MSM and by exposure site: additional anal and pharyngeal swabs for chlamydia and gonorrhoea PCR (plus MCS). NAAT/PCR from oropharyngeal swab, first-pass urine and anorectal swab can be self-collected.
- Suspected PID: test for C. trachomatis, N. gonorrhoeae and M. genitalium.
- Genital sore: dry swab for herpes and syphilis PCR.
Imaging
- Imaging is not routine. In suspected complications (e.g. tubo-ovarian abscess in PID, or to exclude torsion in acute scrotum), imaging and specialist input are guided by the clinical picture.
5. Management
General principles:
- Treat early and empirically in symptomatic patients rather than waiting for results, using the syndromic regimens above.
- Cover co-infection: because chlamydia and gonorrhoea frequently co-exist, syndromic treatment covers both.
Gonorrhoea (confirmed or syndromic):
- Ceftriaxone 500 mg IM into the gluteal muscle, combined with azithromycin.
- For pharyngeal gonorrhoea, use azithromycin 2 g stat rather than 1 g.
- Seek specialist advice for complicated or resistant infection.
Chlamydia / non-gonococcal urethritis:
- Doxycycline 100 mg orally twice daily for 7 days is first-line for uncomplicated genital chlamydia and urethritis.
- Anorectal chlamydia is treated with a longer course: doxycycline 100 mg twice daily for 21 days.
- Avoid single-dose azithromycin as first-line to limit M. genitalium resistance.
M. genitalium:
- Azithromycin 1 g stat, then a further 1 g stat on day 8 (resistance-guided treatment; seek advice as resistance is common).
PID:
- Treat empirically covering chlamydia and gonorrhoea (and anaerobes where relevant). If an IUD is present and PID is mild, it is reasonable to leave the IUD in situ if the patient is monitored for improvement. If the IUD is to be removed, this is usually recommended after more than 48 hours of antibiotics, and alternative contraception will be needed.
- Review at 48 to 72 hours to assess adherence and response. If no clinical improvement within 72 hours, consider admission.
- Further review at 1 to 2 weeks to confirm adequate response, adherence and treatment of contacts, and repeat pregnancy test if clinically indicated.
Public health and follow-up management (gonorrhoea and applicable to chlamydia):
- Advise no sexual contact for 7 days after treatment is commenced, or until the course is completed and symptoms resolve, whichever is later.
- Advise no sex with partners from the last 2 months until those partners have been tested and treated if necessary.
- Recommend partner notification and use the Australasian Contact Tracing Manual for guidance.
- Notify the state or territory health department.
- Provide a patient factsheet.
- Test for other STIs if not done at first presentation.
- Consider HIV pre-exposure prophylaxis (PrEP) for appropriate patients.
Allergy caution: ceftriaxone is contraindicated in severe or immediate allergy to cephalosporins or penicillins; be alert to cross-reactivity between penicillins, cephalosporins and carbapenems. Seek senior advice in renal impairment.
6. Australian-specific considerations
- Notifiable diseases: both gonorrhoea and chlamydia must be reported to the state or territory health department.
- Opportunistic screening: annual chlamydia testing is recommended in young people aged 15 to 29, using NAAT on urine or self-collected swabs.
Clinical pearls
- Co-infection is the rule, not the exception: treat syndromically for both gonorrhoea and chlamydia in any symptomatic presentation, without waiting for NAAT results.
- Doxycycline 100 mg twice daily for 7 days is the preferred first-line agent for uncomplicated genital chlamydia and non-gonococcal urethritis; single-dose azithromycin is no longer recommended as first-line because it drives Mycoplasma genitalium resistance.
- Anorectal chlamydia requires a longer course: doxycycline 100 mg twice daily for 21 days, compared with 7 days for genital infection.
- Pharyngeal gonorrhoea needs a higher azithromycin dose: use azithromycin 2 g stat (not 1 g) when pharyngeal infection is confirmed or suspected.
- A negative NAAT does not exclude PID: clinical features of cervical motion tenderness, adnexal tenderness and mucopurulent cervicitis are sufficient to start empirical treatment.
- Always exclude testicular torsion first in any man presenting with an acute painful swollen scrotum before attributing symptoms to epididymo-orchitis.
- Partner notification and no-sex advice are mandatory components of management: advise no sexual contact for 7 days after treatment, and no sex with partners from the last 2 months until those partners have been tested and treated.
- Ceftriaxone allergy: be alert to cross-reactivity between penicillins, cephalosporins and carbapenems, and seek senior advice before substituting agents in a patient with a relevant allergy history.