Chlamydia trachomatis Overview

Overview

This lecture discusses Chlamydia trachomatis, focusing on its transmission, lifecycle, symptoms, complications, diagnosis, treatment, and prevention.

Epidemiology & Transmission

• Chlamydia trachomatis is a Gram-negative bacterium and the most common sexually transmitted infection (STI), especially in people under 25 years old.
• Transmission mainly occurs through sexual activity, including vaginal, anal, and oral sex.
• Risk factors include:
  • Young age and being sexually active
  • Having new or multiple sexual partners
  • Sexual contact with an infected person
  • Not using barrier contraception (e.g., condoms)
  • Previous chlamydia infection

Lifecycle & Pathophysiology

• Chlamydia has a unique two-phase lifecycle:
  • Elementary body: Infectious form that invades epithelial cells of the urogenital tract.
  • Reticulate body: Metabolically active, non-infectious form that replicates inside host cells.
• After entering the host cell, elementary bodies convert to reticulate bodies, which multiply and then revert to elementary bodies.
• These elementary bodies group into large inclusion bodies. After 2–3 days, the host cell ruptures, releasing new infectious particles to invade nearby cells.
• Chlamydia is an obligate intracellular bacterium and cannot be grown in standard bacterial cultures.
• Infected epithelial cells cause inflammation in the urethra or cervix. In women, the infection can ascend to the upper reproductive tract, leading to pelvic inflammatory disease (PID). In men, it can cause epididymitis or prostatitis.

Clinical Presentation

• Many chlamydia infections are asymptomatic, especially in women.
• Females:
  • Cervicitis: vaginal discharge, painless sex (dyspareunia), post-coital or intermenstrual bleeding
  • Urethritis: symptoms similar to urinary tract infection (frequency, dysuria)
• Males:
  • Urethritis: pain on urination (dysuria), scant watery discharge
• Both sexes can develop proctitis (rectal inflammation) and pharyngitis (throat infection).

Complications

• Women:
  • Pelvic inflammatory disease (PID): infection can spread to uterus, fallopian tubes, and ovaries, leading to infertility and chronic pelvic pain
  • Ectopic pregnancy
• Men:
  • Epididymitis
  • Prostatitis
• Both:
  • Reiter's syndrome (reactive arthritis): classic triad of urethritis, conjunctivitis, and arthritis
  • Proctitis and pharyngitis
• Pregnancy:
  • Increased risk of preterm delivery, low birth weight, and ectopic pregnancy
  • Infants born to untreated mothers are at risk for neonatal conjunctivitis and pneumonia
• Reinfection is common; retesting after treatment is recommended.
• Chlamydia often co-occurs with other STIs, especially gonorrhea.

Diagnosis

• The preferred diagnostic method is the nucleic acid amplification test (NAAT), which is highly sensitive.
  • Can be performed using a vaginal swab (self-collected or by a clinician), first-catch urine sample, urethral swab (in men), or conjunctival swab.
• Routine bacterial culture is not used due to low sensitivity and high cost.
• Differential diagnosis includes other STIs (e.g., gonorrhea), bacterial vaginosis, candidal vulvovaginitis, trichomoniasis, and pelvic inflammatory disease.

Treatment & Prevention

• First-line antibiotics: doxycycline (oral) or azithromycin (azithromycin is preferred during pregnancy).
• Screening for other STIs is important, as co-infection with gonorrhea, HIV, or hepatitis B is common.
• Patients should avoid sexual activity until treatment is completed.
• Contact tracing and partner notification are essential:
  • Patients should inform their sexual partners or provide information for healthcare professionals to notify partners.
• Retesting after treatment is recommended to ensure the infection has cleared.

Key Terms & Definitions

• Gram-negative bacteria: Bacteria with a thin cell wall that does not retain crystal violet dye.
• Obligate intracellular: Organisms that can only replicate inside living host cells.
• Elementary body: The infectious form of chlamydia that invades host cells.
• Reticulate body: The non-infectious, metabolically active form that replicates inside cells.
• Cervicitis: Inflammation of the cervix.
• Urethritis: Inflammation of the urethra.
• Pelvic Inflammatory Disease (PID): Infection of the female upper genital tract.
• Reiter's syndrome: Triad of urethritis, conjunctivitis, and reactive arthritis.
• NAAT: Nucleic acid amplification test, a sensitive diagnostic tool for detecting chlamydia.

Action Items / Next Steps

• Review the symptoms and complications of chlamydia in both men and women.
• Study the lifecycle and pathophysiology of Chlamydia trachomatis.
• Understand diagnostic methods, especially NAAT, and recognize the importance of differential diagnosis.
• Learn about treatment options and the importance of screening for co-infections.
• Ensure knowledge of partner notification, contact tracing, and prevention strategies to reduce reinfection and transmission.