Chlamydia

• Who first described Chlamydia and in what year?

  Halberstaedter and von Prowazek in 1907
• What did Halberstaedter and von Prowazek observe in their study of Chlamydia?


  Cytoplasmic inclusions in conjunctival scrapings from children with trachoma and monkeys
• What are the two human pathogens in the Chlamydia genus?

  • C. trachomatis: causes ocular and genital infections
  • C. pneumoniae: causes mainly respiratory disease
• How many species are there in the Chlamydia genus?

  Nine species
• Which species of Chlamydia primarily infects birds?


  C. psittaci
• What are the clinical manifestations of C. trachomatis infections in the eye?

  Trachoma, inclusion conjunctivitis, and ophthalmia neonatorum
• What are the diseases caused by C. trachomatis in the genital tract?

  • Non-specific urethritis
  • Proctitis
  • Epididymitis
  • Cervicitis
  • Urethritis
  • Endometritis
  • Salpingitis
  • PID
  • Perihepatitis
• What are the sequelae of C. trachomatis infections in the eye?

  Conjunctival scarring, trichiasis, and blindness
• Which serovars of C. trachomatis cause trachoma?

  Serovars A, B, Ba, and C
• What is the classification basis for C. trachomatis serovars?

  Antigenic cross-reactivity in the micro-immunofluorescence test
• What is the infectious cycle of Chlamydia characterized by?

  Two developmental forms: elementary bodies (EB) and reticulate bodies (RB)
• What is the genome size of C. trachomatis?

  1.04 Mb
• How do Chlamydia bacteria maintain their rigidity?

  By extensive disulphide linking of the major outer membrane protein
• What is the role of the elementary body (EB) in Chlamydia's lifecycle?

  It is the transmissible form that attaches to and enters a susceptible epithelial cell
• What happens to the elementary body after it enters the host cell?

  It differentiates into a larger, non-infectious reticulate body
• What is the initial response to Chlamydia infection in epithelial cells?


  A polymorphonuclear leukocyte response
• What are the target cells for the trachoma biovar of C. trachomatis?


  • Squamo-columnar epithelial cells of the endocervix and upper genital tract in women
  • Conjunctiva, urethra, and rectum in both men and women
  • Epididymis and prostate
  • Infant columnar epithelial cells of the respiratory tract
• What is the role of cytokines produced by infected epithelial cells?

  They direct the initial innate and acquired responses to chlamydial infection
• What characterizes the pathology of LGV biovar of C. trachomatis?

  Granuloma formation with development of small abscesses
• How does natural infection with C. trachomatis affect future infections?


  It appears to confer little protection against reinfection
• What is Trachoma and its prevalence?


  • Chronic keratoconjunctivitis caused by repeated infections with serovars A, B, Ba, and C of C. trachomatis
  • Highest prevalence in sub-Saharan Africa
  • Active cases are concentrated in Ethiopia, India, Nigeria, Sudan, and Guinea
• What is the economic burden of Trachoma estimated to be annually?

  $5.3 billion
• In which age group does active C. trachomatis infection mostly occur?


  Children
• What complications can arise from C. trachomatis infections in adulthood?

  Low vision and blindness
• What is the typical age for the first infection of Trachoma in endemic areas?

  Within the first 2 years of life
• What is trichiasis and its consequence?

  Distortion of the eyelid causing eyelashes to abrade the cornea, leading to ulceration and vision loss
• What are the oculogenital diseases caused by C. trachomatis in adults?

  • Inclusion conjunctivitis
  • Acute follicular conjunctivitis
  • Genital tract infections
• What is the presumed mode of transmission for inclusion conjunctivitis?

  Autoinoculation of the eye with infected genital secretions
• What is the most common cause of bacterial sexually transmitted infection in the world?

  C. trachomatis
• How does the risk of acquiring C. trachomatis compare to N. gonorrhoeae?

  It is substantially less than that of N. gonorrhoeae
• What are the differences in clinical presentation between chlamydial and gonococcal urethritis?

  • Chlamydial urethritis often has milder symptoms
  • Gonococcal urethritis typically presents with more severe symptoms
• What sensation is often experienced in the eye with inclusion conjunctivitis?

  Foreign body sensation
• What is the typical duration of hyperemia and mucoid discharge in inclusion conjunctivitis?

  The first 2 weeks
• What is the prevalence of concurrent C. trachomatis genital tract infection in adults with inclusion conjunctivitis?

  Slightly more than half
• How is inclusion conjunctivitis primarily transmitted?

  Through autoinoculation of the eye with infected genital secretions
• Can eye-to-eye spread of inclusion conjunctivitis occur without sexual contact?

  Yes, through transfer of infected secretions
• What is the most common cause of bacterial sexually transmitted infection worldwide?

  C. trachomatis
• How does the risk of acquiring C. trachomatis compare to N. gonorrhoeae with a single episode of sexual intercourse?

  The risk of C. trachomatis is substantially less
• What is a reliable method to distinguish between chlamydial and gonococcal urethritis?

  Testing is required, as clinical grounds alone are insufficient
• What is the incubation period for symptomatic chlamydial urethritis?

  7 to 14 days