Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.
Chlamydia and gonorrhoea
Infectious diseases, microbiology and sexual health · UK scope · Sources checked 27 Aug 2026 · Clinical review pending
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Disseminated or ascending STI
Sepsis, severe pelvic pain, pregnancy pain, peritonism, testicular pain, hot swollen joints, pustular rash or visual symptoms may indicate PID, epididymo-orchitis, disseminated gonococcal infection or ocular disease.
Action: Use ABCDE when unwell, collect blood and site cultures without delaying treatment, involve sexual health and the relevant gynaecology, urology, ophthalmology or rheumatology team, and begin syndrome-specific intravenous or parenteral therapy.
Overview
Diagnose chlamydial and gonococcal infection at every exposed anatomical site, preserve gonococcal susceptibility, treat with current UK regimens and prevent reinfection through partner care.
Chlamydia trachomatis and Neisseria gonorrhoeae infect columnar epithelium of the cervix, urethra, rectum, pharynx and conjunctiva. Symptoms overlap, coinfection occurs and neither infection can be excluded by a normal examination.
Chlamydia is an obligate intracellular bacterium whose often silent infection can ascend to cause salpingitis, infertility and ectopic pregnancy. Gonococcus is a Gram-negative diplococcus with rapid inflammatory injury and exceptional capacity to acquire antimicrobial resistance.
NAAT offers high sensitivity and is the routine diagnostic method. Gonococcal culture remains essential before treatment whenever possible because it confirms viable organisms and provides susceptibility data needed for individual and national resistance control.
Treatment is only one part of cure. Partners require confidential notification and testing, exposed sites must be sampled, complications need longer syndrome-specific regimens and repeat infection is common without follow-up.
Key points
Chlamydia is often asymptomatic but can cause cervicitis, urethritis, PID, epididymo-orchitis and reactive arthritis.
Aetiology
01
Chlamydial sexual transmission
C trachomatis passes through genital, rectal, pharyngeal or perinatal exposure and frequently persists without symptoms at the infected mucosal site.
02
Gonococcal sexual transmission
N gonorrhoeae infects mucosal surfaces after close sexual contact and may disseminate through blood in susceptible hosts.
03
Perinatal exposure
Untreated cervical infection exposes the neonate during birth, causing conjunctival or respiratory disease according to organism.
04
Reinfection from partners
Untreated current partners commonly reintroduce infection after an otherwise effective course and drive repeated upper-tract injury.
Pathophysiology
1
Intracellular chlamydial cycle
Elementary bodies enter epithelial cells and transform into replicating reticulate bodies before releasing infectious progeny, enabling persistent infection with limited symptoms.
2
Gonococcal mucosal inflammation
Pili and outer-membrane proteins enable gonococcal attachment and invasion, provoking intense neutrophilic inflammation, dysuria and purulent mucosal discharge.
3
Ascending genital spread
Organisms ascend from cervix into endometrium and fallopian tubes, causing scarring, adhesions and impaired fertility, especially after delayed or repeated infection.
4
Immune evasion
Antigenic variation and incomplete protective immunity permit repeated gonococcal and chlamydial infection, so previous infection does not protect against reinfection.
5
Bloodstream dissemination
Gonococcus occasionally spreads haematogenously to skin, tendon sheaths and joints, producing the characteristic dermatitis, tenosynovitis and migratory arthralgia syndrome.
Clinical features and red flags
Chlamydial cervicitis
Postcoital or intermenstrual bleeding, mucopurulent cervical discharge, dysuria and pelvic discomfort may occur, but most infection is silent.
Gonococcal urethritis
Abrupt dysuria and profuse purulent urethral discharge strongly suggests gonorrhoea, particularly after a short incubation.
Rectal infection
Anorectal pain, discharge, bleeding or tenesmus may occur after receptive anal exposure, while many infections remain asymptomatic.
Pharyngeal infection
Sore throat is uncommon and nonspecific; exposure-site testing is required because silent pharyngeal gonorrhoea sustains transmission and resistance.
Upper-tract complicationRed flag
Pelvic pain, deep dyspareunia, cervical excitation, testicular pain or epididymal swelling indicates spread beyond uncomplicated infection.
Disseminated gonorrhoeaRed flag
Migratory arthralgia, tenosynovitis, sparse pustules and later septic arthritis can occur with minimal genital symptoms.
Red flags requiring action
Pelvic pain with cervical excitation or adnexal tenderness requires immediate PID treatment before NAAT results.
Acute unilateral testicular pain or swelling needs urgent torsion exclusion before attributing symptoms to epididymitis.
Hot joints, tenosynovitis, pustular skin lesions or fever suggests disseminated gonococcal infection.
Investigations
01Vulvovaginal swab or first-catch urine NAATFirst step
Why
Detect chlamydia and gonorrhoea from the genital site with a validated molecular assay.
Interpretation and limitations
Self-taken vulvovaginal swab performs well; first-catch rather than midstream urine is used in people with a penis.
02Rectal and pharyngeal NAAT
Why
Detect infection at exposed extragenital sites that urine or genital sampling would miss.
Interpretation and limitations
Use a site-specific sexual history; a negative genital result does not exclude rectal or pharyngeal infection.
03Gonococcal culture
Why
Confirm viable N gonorrhoeae and obtain antimicrobial susceptibility before treatment.
Interpretation and limitations
Culture symptomatic and NAAT-positive sites before antibiotics where feasible; prompt transport is important because the organism is fragile.
04Pregnancy test
Why
Guide medication choice and assess ectopic or obstetric risk in pelvic pain.
Interpretation and limitations
Doxycycline is avoided during pregnancy; pain or bleeding with a positive test requires urgent pregnancy-location assessment.
05HIV and syphilis testing
Why
Identify common concurrent infections and opportunities for prevention.
Differential diagnosis
01
Non-gonococcal urethritis
Mycoplasma genitalium, trichomonas and non-infective irritation produce dysuria and discharge with negative gonococcal testing; exposure-led NAAT clarifies the cause.
02
Vaginitis
BV, Candida and trichomonas primarily cause vaginal odour, itch or inflammation and can coexist with cervicitis.
03
Urinary tract infection
Cystitis causes frequency and dysuria without urethral discharge or cervical inflammation; urinalysis, culture and exposed-site NAAT separate concurrent disease.
04
Ectopic pregnancy
Pregnancy with pain and bleeding requires urgent ultrasound and serial hCG assessment because a positive cervical STI result does not exclude ectopic pregnancy.
05
Testicular torsion
Sudden severe unilateral testicular pain is a surgical emergency that must be excluded before diagnosing epididymo-orchitis.
Management
01SAMPLETest every exposed siteFirst stepThere is STI exposure, genital discharge, dysuria, bleeding or a partner notification.+
1Take a confidential sexual history covering vaginal, anal and oral exposure, symptoms, contraception, pregnancy possibility and safeguarding.
2Collect genital or urinary NAAT plus rectal and pharyngeal samples where exposed, before antibiotics when clinically safe.
3If gonorrhoea is suspected or NAAT positive, obtain culture from every positive or symptomatic site for susceptibility.
4Offer HIV and syphilis testing, hepatitis assessment and vaccination or PrEP discussion according to exposure.
02CHLAMYDIATreat uncomplicated chlamydiaNAAT confirms uncomplicated chlamydia without PID, epididymo-orchitis, pregnancy or lymphogranuloma venereum.+
1Give doxycycline 100 mg orally twice daily for seven days after checking pregnancy and interactions.
Complications
01
Pelvic inflammatory disease
Ascending infection produces endometritis and salpingitis; repeated or delayed episodes increase tubal scarring, chronic pain, infertility and ectopic pregnancy risk.
02
Epididymo-orchitis
Urethral organisms ascend the male genital tract, causing unilateral pain and swelling; abscess, infarction, chronic pain or impaired fertility can follow.
03
Disseminated gonorrhoea
Bloodstream spread causes fever, pustular lesions, tenosynovitis, migratory arthralgia and septic arthritis, which can rapidly damage the affected joint.
04
Perihepatitis
Upper-genital inflammation extends to the hepatic capsule, producing right-upper-quadrant pain and perihepatic adhesions despite no primary liver disease.
05
Neonatal infection
Perinatal exposure causes gonococcal ophthalmia or chlamydial conjunctivitis and pneumonia with preventable visual and respiratory harm.
Monitoring and follow-up
Confirm symptom improvement while recognising that absence of symptoms never proves microbiological clearance.
Review gonococcal culture and susceptibility promptly and recall the patient if resistance makes initial treatment unreliable.
Arrange gonorrhoea test of cure at the recommended interval for pharyngeal infection, alternative regimens, resistance or persistent symptoms.
Arrange chlamydia test of cure in pregnancy and other defined situations, avoiding NAAT too soon because residual nucleic acid can persist.
Offer reinfection testing at about three months and repeat HIV or syphilis tests after relevant window periods.
Confirm current partner notification and treatment through confidential sexual-health processes.
Sampling follows sexual exposure, not gender or orientation; genital-only testing misses clinically important rectal and pharyngeal infection.
Culture protects future treatment
NAAT detects gonococcus sensitively, while culture supplies the susceptibility evidence needed to recognise treatment failure and resistance.
PID is clinical
A negative cervical test cannot exclude ascending infection, so pelvic tenderness with risk is treated promptly.
Pharynx is a resistance niche
Lower drug exposure and commensal Neisseria make pharyngeal gonorrhoea harder to eradicate and important for genetic exchange.
Retesting is not test of cure
A later reinfection screen detects new exposure; a test of cure answers whether the treated episode has cleared.
Torsion remains first
An STI history must not delay urgent surgical assessment of sudden testicular pain and an abnormal testicular lie.
Common pitfalls
01
Do not use a midstream urine sample when first-catch urine is required for NAAT.
02
Do not omit rectal or pharyngeal sampling after exposure at those sites.
03
Do not treat suspected gonorrhoea without obtaining culture when feasible.
04
Do not assume ceftriaxone treats concurrent chlamydia.
05
Do not wait for results before treating clinical PID.
06
Do not use a positive early post-treatment NAAT alone to declare viable chlamydia.
Practice
Two practice questions
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Question 1 of 2
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Infectious diseases, microbiology and sexual healthOriginal SBA
Testing exposed sites
An asymptomatic adult reports receptive anal and oral sex with a partner newly diagnosed with gonorrhoea. A urine NAAT is negative. What is the best next step?
Sources and review status4 sources · checked 27 Aug 2026 · clinical review pending+
Sources
Sources and review status
National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.
Gonorrhoea frequently causes purulent urethral or cervical discharge but pharyngeal and rectal infection are commonly silent.
Take NAAT from every exposed site: vulvovaginal swab or first-catch urine, plus rectal or pharyngeal samples according to sexual history.
When gonorrhoea is suspected, obtain culture before treatment so antimicrobial susceptibility is preserved.
Use doxycycline 100 mg orally twice daily for seven days for uncomplicated chlamydia in a suitable non-pregnant adult.
Use ceftriaxone 1 g intramuscularly once for uncomplicated gonorrhoea when susceptibility is unknown under current UK guidance.
If chlamydia has not been excluded, add effective chlamydia treatment rather than assuming ceftriaxone covers it.
Arrange partner notification, abstinence until the advised interval after both patient and partners complete treatment, and site-specific test of cure when indicated.
Purulent conjunctivitis with gonococcal risk threatens rapid corneal damage and needs emergency ophthalmology.
Pregnancy with pain, bleeding or suspected cervical infection requires same-day maternity and sexual-health review.
Pharyngeal gonorrhoea, persistent symptoms or suspected treatment failure requires culture, test of cure and specialist resistance management.
Interpretation and limitations
Offer according to national sexual-health practice and exposure window; arrange repeat testing when the initial test is too early.
06PID or epididymal assessment
Why
Identify upper-tract infection requiring immediate broader and longer treatment.
Interpretation and limitations
PID is a clinical diagnosis and treatment should not wait for NAAT; Doppler ultrasound is used when torsion or another testicular diagnosis remains possible.
07Joint fluid and blood cultures
Why
Confirm disseminated gonococcal infection and exclude alternative septic arthritis.
Interpretation and limitations
Aspirate an affected joint before antibiotics when safe; genital, rectal and pharyngeal NAAT and cultures improve organism recovery.
2
AlternativeUse the current pregnancy or intolerance alternative through sexual-health guidance rather than shortening doxycycline.
3Advise no sex until treatment is completed, the recommended post-treatment interval has passed and current partners are treated.
4Arrange partner notification and retesting for reinfection at about three months according to national practice.
03GONORRHOEATreat and document susceptibilityGonorrhoea is confirmed or treatment is required before results because follow-up or complication risk is high.+
1Obtain gonococcal culture before treatment whenever possible and document all exposed sites.
2AlternativeGive ceftriaxone 1 g intramuscularly once when susceptibility is unknown, using a specialist alternative only for genuine contraindication.
3Add doxycycline 100 mg twice daily for seven days if chlamydia has not been excluded and pregnancy does not preclude it.
4AlternativeArrange test of cure for pharyngeal disease, alternative treatment, resistance concern, persistent symptoms or as current guidance requires.
04COMPLICATEDEscalate beyond single-site treatmentEscalationPID, epididymo-orchitis, disseminated infection, conjunctivitis or treatment failure is suspected.+
1Start the full syndrome-specific regimen without waiting for routine NAAT results and involve the appropriate acute specialty.
2Obtain culture, blood or joint specimens before treatment where this does not cause dangerous delay.
3Investigate abscess, torsion, septic arthritis, endocarditis or ocular injury according to presentation.
4Confirm clearance and complete extended partner and public-health management with a specialist sexual-health service.
Key medicines and prescribing safety4 treatments · regimens, roles and cautions+
Provides effective intracellular treatment and is preferred for rectal chlamydia.
Doxycycline for uncomplicated chlamydia
Give 100 mg orally twice daily for seven days in a suitable non-pregnant adult with uncomplicated genital, pharyngeal or rectal infection.
Avoid in pregnancy; take with water while upright, separate from iron and antacids, counsel photosensitivity and check retinoid and anticoagulant interactions.
Treats genital, rectal and pharyngeal gonorrhoea while resistance surveillance guides future choices.
Ceftriaxone for uncomplicated gonorrhoea
Give 1 g intramuscularly as a single dose when susceptibility is unknown, following the current UK gonorrhoea guideline.
Obtain culture first, clarify severe beta-lactam allergy, use lidocaine diluent only as specified, and arrange test of cure where required.
Provides an alternative to doxycycline for uncomplicated chlamydia during pregnancy.
Azithromycin in pregnancy chlamydia pathway
Give 1 g orally as a single dose when current specialist pregnancy guidance selects azithromycin after individual assessment.
Confirm local recommendation, QT and liver risk, interactions and vomiting; arrange pregnancy test of cure and later reinfection testing.
Preserves effective treatment while avoiding unreliable empirical oral cephalosporin or macrolide monotherapy.
Gonorrhoea allergy or susceptibility alternative
Use only the exact culture-directed or specialist regimen from current UK guidance when ceftriaxone cannot be given.
Discuss severe allergy and resistance with sexual-health microbiology, retain culture, document the regimen and ensure test of cure.