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Chlamydia trachomatis

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Overview

Chlamydia trachomatis is an obligate, intracellular Gram-negative bacterium that is the most common sexually transmitted infection (STI) in the UK. Infection can cause urethritis in men and women, and also cervicitis in women. It can also cause infections of the conjunctiva, rectum, and nasopharynx.

Definitions

An uncomplicated infection is when an infection has not ascended the upper genital tract.

A complicated infection is when the infection has spread to the upper genital tract, which can cause pelvic inflammatory disease (PID) in women and epididymo-orchitis in men.

Pathophysiology

Upon entering the body, Chlamydia trachomatis enters cells and forms inclusion bodies, which mature and cause the cell to rupture, resulting in free bacteria entering other cells and repeating the cycle. Due to this lifecycle, it cannot be cultured on artificial media.

In some cases, infection can ascend the urogenital tract and cause an infection of the pelvis (pelvic inflammatory disease) or peri-hepatitis (Fitzhugh-Curtis syndrome). In men, it can cause epididymo-orchitis or prostatitis.

Associations

Chlamydia trachomatis has multiple serotypes that are capable of causing different clinical syndromes:

  • Genitourinary infection – epididymitis, urethritis, proctitis, cervicitis, PID
  • Reactive arthritis – urethritis, conjunctivitis, and arthritis post-STI
  • Lymphogranuloma venereum – characterised by a painless ulcer, followed by painful inguinal lymphadenopathy, constitutional symptoms, and proctitis.
  • Inclusion conjunctivitis – an STI of the eye which can happen due to autoinoculation or splash from genital fluids. It may also occur during delivery due to spread from the maternal genital tract, however, this does not cause corneal scarring. 
  • Trachoma – an infection of the eye causing chronic keratoconjunctivitis and corneal scarring, which can cause blindness.
  • Neonatal pneumonia – due to spread from the maternal genital tract

Epidemiology

  • Rates of Chlamydia infection diagnoses were highest in the 15-24 years age group and made up around 60% of reported cases
  • In the UK and globally, Chlamydia is the most common bacterial STI

Risk Factors

Risk factors include:

  • <25 years old
  • New sexual partner
  • Multiple sexual partners
  • Lack of barrier contraception use
  • Sexual abuse

Presentation

Overview

Chlamydia infection is asymptomatic in around 70% of women and 50% of men. Features can be mild and may include:

  • In women, features of cervicitis may be present – increased and/or abnormal vaginal discharge, post-coital/intermenstrual bleeding, dyspareunia, cervical motion tenderness
  • In men, features of urethritis may be present – dysuria, urethral discharge, pain
  • Features of associated conditions may also be present

Investigations

Overview

Nuclear acid amplification testing (NAAT) is the investigation of choice. The type of sample differs in women and men:

  • Women – vulvovaginal swab is first-line:
    • Other options include an endocervical swab or first-catch urine sample
  • Men – first void urine sample is first-line:
    • Other options include a urethral swab

Screening

Screening for asymptomatic Chlamydia may be offered if any of the following apply. It should be performed at presentation and if negative, 2 weeks following exposure:

  • All sexually active people <25 years old annually, or more frequently if they have changed partner
  • All people seeking termination of pregnant
  • All people attending genitourinary clinics
  • All people with concerns about sexual exposure
  • Sexual partners in someone with Chlamydia infection
  • <25 years old who has had treatment for Chlamydia in the last 3 months
  • People who have had ≥2 partners in the last 12 months

Management

Overview

For non-pregnant people:

  • 1st-line: oral doxycycline for 7 days
    • If contraindicated/inappropriate: azithromycin is an alternative

For pregnant people:

  • 1st-line: azithromycin, erythromycin, or amoxicillin

Partner notification and screening

People with Chlamydia should be encouraged to attend a genitourinary clinic for screening for other STIs (e.g. gonorrhoea, hepatitis B, HIV, and syphilis) and partner notification:

  • All partners from the last 6 months or the most recent sexual partners should be contacted
  • Contacts of confirmed Chlamydia cases are offered treatment before test results are confirmed (‘test then treat’)

Complications

Pelvic inflammatory disease (PID) – can occur in up to 16% of people with untreated Chlamydia and can increase the risk of infertility, ectopic pregnancy, and chronic pelvic pain. Prolonged exposure to Chlamydia trachomatis (e.g. by persisting/recurring infection) can cause tubal tissue damage. The risk is relatively low if Chlamydia is treated.

Epididymo-orchitis – can occur in men with untreated Chlamydia, particularly men <35 years old, due to the ascension of infection through the spermatic cord.

Obstetric complications – these include an increased risk of premature rupture of membranes, preterm delivery, low birth weight, endometritis, and infection of the eyes, lungs, and genitals of the neonate.

Reactive arthritis – Chlamydia trachomatis can trigger sterile inflammation of the synovial membranes at another site, resulting in arthralgia. Other features include conjunctivitis and urethritis. This occurs in up to 8% of people.

Perihepatitis (Fitz-Hugh-Curtis syndrome) – Chlamydia trachomatis can ascend from the vagina into the endometrium, into the Fallopian tubes, and into the peritoneal cavity, causing inflammation of the hepatic capsule, resulting in right upper quadrant pain.

Lymphogranuloma venereum (LGV) – rates are higher in men who have sex with men and people with HIV.

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