Chlamydia
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Background
Chlamydia is a sexually transmitted infection (STI) caused by the bacterium Chlamydia trachomatis, an obligate intracellular Gram-negative bacterium. It primarily affects the genitourinary tract but can also infect the rectum, conjunctiva, and pharynx. Chlamydia is the most commonly diagnosed bacterial STI in the UK and a leading preventable cause of infertility worldwide.Chlamydia is a gram negative coccobacillus (It falls under the rod classification and has an ovoid morphology).
Prevalence in the UK
In 2023 there were 194,970 new diagnoses of chlamydia in England, with around 60% occurring in individuals aged 15–24 years. This age group is particularly affected, highlighting the importance of targeted screening and prevention efforts.Risk factors
Key risk factors for chlamydial infection include:- Age under 25 years
- Having multiple sexual partners in the past year
- Recent change in sexual partner
- Inconsistent or non-use of condoms
- Use of non-barrier contraception
- Co-infection with another STI
- Low socio-economic status
- Having a sexual partner who tests positive for chlamydia
Transmission
Chlamydia is transmitted through unprotected vaginal, anal, or oral sex. It can also be passed from mother to child during childbirth. The incubation period ranges from 7 to 21 days, after which symptoms may develop, although many infections remain asymptomatic.
Incubation period
The incubation period ranges from 7 to 21 daysPathogenesis
Chlamydia trachomatis infects columnar epithelial cells of the mucous membranes, leading to local inflammation and tissue damage. The infection can ascend the reproductive tract, causing complications such as pelvic inflammatory disease (PID) in women and epididymo-orchitis in men.Clinical features
Chlamydia is often asymptomatic: approximately 70-80% of infected women and 50% of infected men show no symptoms.In women:
- Abnormal vaginal discharge
- Dysuria (painful urination)
- Intermenstrual or postcoital bleeding
- Lower abdominal pain
- Deep dyspareunia (pain during intercourse)
- Cervicitis with mucopurulent discharge
In men:
- Urethral discharge
- Dysuria
- Testicular pain and swelling (epididymo-orchitis)
- Perineal discomfort
Other presentations:
- Proctitis with rectal discomfort and discharge
- Pharyngeal infection (usually asymptomatic)
- Reactive arthritis (urethritis, arthritis, conjunctivitis triad)
- Perihepatitis (Fitz-Hugh–Curtis syndrome)
Table 1: Complications
| Complication | Description |
|---|---|
| Pelvic Inflammatory Disease (PID) | Ascending infection in women that can cause fallopian tube damage, pain, and abscess formation |
| Infertility | Tubal scarring and adhesions from chronic or repeated infections can lead to tubal factor infertility |
| Ectopic Pregnancy | Tubal damage increases the risk of implantation outside the uterus, particularly in the fallopian tubes |
| Chronic Pelvic Pain | Persistent pelvic discomfort resulting from chronic inflammation and adhesions |
| Reactive Arthritis (Reiter’s syndrome) | Post-infectious autoimmune condition causing arthritis, conjunctivitis, and urethritis, more common in men |
| Epididymo-orchitis | Ascending infection in men causing inflammation of the epididymis and/or testicle, with possible fertility impact |
| Neonatal Conjunctivitis (Ophthalmia Neonatorum) | Conjunctival inflammation in newborns exposed during birth, may cause corneal damage if untreated. Chlamydial neonatal conjunctivitis is associated with pneumonitis and pneumonia |
| Neonatal Pneumonia | Staccato cough in infants due to vertical transmission, typically afebrile and occurring within first 3 months of life |
Diagnosis
Nucleic acid amplification tests (NAATs) are the gold standard for chlamydia detection. In women, self-collected vulvovaginal swabs are preferred; in men, first-catch urine samples are standard. Testing is recommended for:
- Sexually active individuals under 25 years (annually or upon partner change)
- Individuals with symptoms suggestive of chlamydia
- Sexual partners of infected individuals
Management
First-line Treatment:
- Doxycycline 100 mg orally twice daily for 7 days (contraindicated in pregnancy and breastfeeding).
Alternative regimens (e.g., pregnancy, contraindications):
- Azithromycin 1 g on day 1, then 500 mg once daily for 2 days
- Erythromycin 500 mg twice daily for 10–14 days
- Amoxicillin 500 mg three times daily for 7 days (in pregnancy)
Additional Management Steps:
- Advise abstaining from sexual activity until 7 days after treatment completion and until partners are treated
- Partner notification and treatment
- Screening for other STIs, including HIV and gonorrhoea
- Test of cure is generally not required unless the patient is pregnant, symptoms persist, or there is concern about adherence