Chlamydiaceae. Genus Chlamydia.

Question 1

Classification

Answer 1

Family: Chlamydiaceae

GENUS

Chlamydia: C. Trichomatis

Chlamydophila: C.pneumoniae and C.psittaci

Question 2

Chlamydia Trachomatis

Answer 2

Divided into 3 groups:

A - C —> blindness

D - K —> sexually transmitted infections

L1 - L3 —> lymphogranuloma venereum

Habitat: human genital tract and eyes

Transmission:

• sexual contact
• during passage of neonate through birth canal

Question 3

Morphology

Answer 3

• small round to ovoid bacteria that cannot be stained via Gram’s stain
• some inclusion bodies retain iodine or the counter stain safarin
• rigid cell wall
• the cell envelope has two lipid layers with cell wall material resembles a gram-negative (but no peptidoglycan nor muramic acid)

Question 4

Growth characteristics

Answer 4

• obligate intracellular parasite —> due to the fact that they cannot produce their own ATP
• exists as:
  1st stage —> Elementary bodies = inactive form = infectious form

2nd stage —> Reticulate bodies = active form that can multiply (active dividing form)

Question 5

Antigenic structure

Answer 5

LPS

Major outer membrane protein (MOMP)

Question 6

Virulence factor

Answer 6

No toxins or virulence factors known

Question 7

Disease

Answer 7

A - C —> blindness

• leading cause of blindness worldwide
• transmission is by hand to eye contact

D - K —> sexually transmitted infections

• characterized by watery discharge
• ascending infection -> cervicitis, saplingitis, oophoritis …
• can lead to —> pelvic inflammatory disease

If baby is infected

• conjunctivitis —> late onset (to differentiate from Gonnorhoeae)
• pneumonia in infants —> cough with really short breaths

L1 - L3 —> Lymphogranuloma venereum
-characterized by tender inguinal lymphadenopathy

Question 8

Microbiological diagnosis

Answer 8

• cytoplasmic inclusions seen on Giemsa stained or fluorescent antibody stained smear
• glycogen-filled cytoplasmic inclusions can be visualised with iodine
• organism grows in cell culture and embryonated eggs, but these are not often used.
• PCR-based assay and Elisa using patient’s urine are available

Question 9

Treatment and prevention

Answer 9

Macrolide (e.g. azithromycin)

• do not use topical macrolides for neonatal conjunctivitis
• oral macrolides are useful for treatment of trachoma

Tetracycline (e.g. doxycycline)

Always treat as if coinfection with Gonorrhoea—> add ceftriaxone

Prevention:

erythromycin is effective in infected mother to prevent neonatal disease

No vaccine is available