Mycobacterium Leprae

Question 1

Classification

Answer 1

Family: mycobacteriaceae

Genus: mycobacterium

Species: Leprae

Transmission:

Respiratory droplets (higher spread seen in lepromatous form compared with tuberculoid form)

Question 2

Morphology

Answer 2

Acid-fast rods
Slender 
Slight curved or straight
Arranged:
- singly
- in parallel bundles (like rows of cigarettes in a packet)
- or globular masses

Question 3

Growth characteristics

Answer 3

Obligate aerobes

Optimal growth at less than body temperature:
> lesions are on cooler parts of the body, such as skin, nose, and superficial nerves

Cannot be cultured in vitro

Question 4

Antigenic structure

Answer 4

Cell wall - 4 layers:

1) innermost: peptidoglycan
2) Liposrabinomanan - highly serodiagnosis
3) mycolic acid
4) outermost- mycosides: protects enzymes and suppressed CMI (predilection to Schwann cells)

Question 5

Virulence factors

Answer 5

• Adhesins: attach itself to Schwann cells.
  > this result in nerve damage and cause leprosy
• it evades cell death by a method not fully understood

Question 6

Disease

Answer 6

Leprosy:

Lepromatous form

Tuberculoid form

Question 7

Microscopical diagnosis

Answer 7

• Acid-fast rods are abundant in lepramatous leprosy, but few are found in the tuberculoid form
• cultures and serologic tests are not done -> grows very slowly
• lepromin skin test is positive in the tuberculoid form only

Question 8

Treatment and prevention

Answer 8

• Dapsone + rifampin for the tuberculoid form
• Dapsone + rifampin + Clofazime for the lepromatous form or if the organism is resistant to dapsone
• treatment is for at least 2 years

Prevention

• Dapsone for close family members
• no vaccine is available