Chlamydia

• What type of bacteria are Chlamydiaceae?

  Gram-negative pathogens
• What are the general characteristics of Chlamydiaceae?

  • Nonmotile
  • Grow and multiply only within vesicles in host cells (obligate intracellular bacteria)
  • Once considered viruses due to small size and intracellular lifestyle
  • Possess DNA, RNA, and functional 70S ribosomes
  • Surrounded by two membranes without peptidoglycan between them
  • Lack cell walls
• What are the two forms in the life cycle of Chlamydiaceae?

  • Elementary bodies (EBs)
  • Reticulate bodies (RBs)
• What is the size and nature of elementary bodies (EBs) in Chlamydiaceae?

  They are small, resistant to environmental extremes, and non-replicative.
• What is the size and nature of reticulate bodies (RBs) in Chlamydiaceae?

  They are larger, metabolically active, and replicate via binary fission within phagosomes.
• Describe the life cycle of Chlamydiaceae.

  1. Elementary bodies (EBs) attach to and enter a host cell.
  2. EBs convert into reticulate bodies (RBs) inside the endosome.
  3. RBs multiply rapidly.
  4. RBs convert back to EBs within an inclusion body.
  5. EBs are released from the host cell via exocytosis.
• What are the two clinically important genera in the Chlamydiaceae family?

  Chlamydia and Chlamydophila
• Which species of Chlamydiaceae are responsible for human disease?

  Chlamydia trachomatis, Chlamydophila pneumoniae, and Chlamydophila psittaci
• How does C. trachomatis enter the human body?


  Through abrasions and lacerations
• What types of cells does C. trachomatis infect?


  Cells of the conjunctiva and cells lining the mucous membranes of the trachea, bronchi, urethra, uterus, uterine tubes, anus, and rectum
• How can C. trachomatis be transmitted?


  Via droplets, hands, contaminated fomites, or flies
• What is trachoma and how can it be transmitted?

  Trachoma is transmitted by ingestion of food and water contaminated with human feces.
• How can infants become infected with C. trachomatis?

  During birth as they pass through an infected birth canal.
• What are the clinical manifestations of chlamydial infection?

  Result from the destruction of infected cells and the inflammatory response.
• What are the two main types of diseases caused by Chlamydia trachomatis?

  1. Sexually transmitted diseases
  2. Ocular disease (trachoma)
• What is urethritis and its prevalence in women and men infected with C. trachomatis?

  Urethritis is asymptomatic in 80% of women and symptomatic in more than 75% of men.
• How can chlamydia trachomatis urethritis be distinguished from gonorrhea?

  It cannot be distinguished based on symptoms alone.
• What happens during lymphogranuloma venereum caused by C. trachomatis?

  A small painless ulcer develops, followed by inflammation and swelling of lymph nodes, then systemic symptoms like fever and chills.
• What serovars cause lymphogranuloma venereum?

  1. trachomatis serovars L1 and L3
• What is trachoma and which serotypes cause it?

  Trachoma is a chronic communicable disease of the eye caused by C. trachomatis serotypes A, B, and C.
• What are the initial symptoms of trachoma?

  Initially, patients have conjunctivitis.
• What happens as trachoma progresses?

  The conjunctivae become scarred, causing the eyelids to turn inward, leading to corneal ulceration and loss of vision.
• What is trichiasis in relation to trachoma?

  Trichiasis is when eyelashes are misdirected and grow inwards towards the eye surface.
• What is adult inclusion conjunctivitis and its characteristics?

  It is an acute follicular conjunctivitis caused by C. trachomatis strains associated with genital infections, characterized by mucopurulent discharge and corneal scarring.
• How can neonatal conjunctivitis occur?

  It can develop in infants exposed to C. trachomatis at birth, leading to eyelid swelling and purulent discharge.
• What is the incubation period for neonatal conjunctivitis?

  5 to 12 days
• What can untreated neonatal conjunctivitis lead to?

  It may lead to blindness and pneumonia.
• What are the laboratory diagnosis methods for chlamydial infections?

  1. Specimens based on the site of infection (e.g., urethral or eye discharge)
  2. Direct sample examination (Giemsa stain, iodine staining, fluorescent antibody technique)
  3. Culture in cell culture
  4. Nucleic acid amplification tests (NAATs)
  5. Antibody detection (limited value)
• What is the significance of chlamydial inclusion bodies inside cells?

  They indicate the presence of Chlamydia within cells and are diagnostic for a C. trachomatis infection.
• What does a direct fluorescent immunoassay reveal in relation to C. trachomatis?

  It reveals the presence of Chlamydia within cells.
• What is the test of choice for diagnosing chlamydia infections?

  Nucleic acid amplification tests (NAATs)
• What specimens can be used for NAATs in diagnosing chlamydia infections?

  First voided urine and urethral discharge
• Why is serologic testing of limited value in diagnosing C. trachomatis infections?

  It cannot differentiate between current and past infections.
• What diseases does Chlamydophila pneumoniae cause?

  Sinusitis, pharyngitis, bronchitis, and pneumonia
• How is Chlamydophila pneumoniae transmitted?

  By respiratory secretions from person to person
• What are the typical symptoms of Chlamydophila pneumoniae infections?

  Malaise and a chronic cough
• What is the diagnostic method for Chlamydophila pneumoniae?

  Fluorescent antibodies demonstrate the intercellular presence of C. pneumoniae.
• What disease does Chlamydophila psittaci cause?

  Psittacosis (parrot fever)
• How is Chlamydophila psittaci transmitted to humans?

  By inhaling aerosolized bird feces or respiratory secretions.
• What are the typical symptoms of psittacosis in humans?

  Flu-like symptoms, and in some cases, severe pneumonia.