Mycobacterium leprae

Mycobacterium leprae

Q. 1

Generation time of Mycobacterium leprae is: 

 A

2-5 days

 B

7-10 days

 C

12-14 days

 D

20-25 days

Q. 1

Generation time of Mycobacterium leprae is: 

 A

2-5 days

 B

7-10 days

 C

12-14 days

 D

20-25 days

Ans. C

Explanation:

Generation time: Is the time interval between two cell divisions or the time required for a bacterium to give rise to two daughter cells.

It is also known as population doubling time. The generation time of lepra bacillus is 12 to 13 days on an average.

Good to know:
M. tuberculosis has generation time of 15-20 hours and for coliform bacillus it is just 20 minutes.
 
Ref: Textbook of Microbiology By, R. Ananthanarayan, C.K. Jayaram Paniker, 7th Edition, Page 18,371.

Q. 2

Which of the following are AFB positive with 5% sulphuric acid –

 A

M. avium

 B

M. leprae

 C

M. tuberculosis

 D

Nocardia

Q. 2

Which of the following are AFB positive with 5% sulphuric acid –

 A

M. avium

 B

M. leprae

 C

M. tuberculosis

 D

Nocardia

Ans. B

Explanation:

Ans. is `b’ i.e., M. leprae


Q. 3

Following grows in the cell free medium except -a

 A

Rickettsia

 B

M leprae

 C

Syphilis

 D

All

Q. 3

Following grows in the cell free medium except -a

 A

Rickettsia

 B

M leprae

 C

Syphilis

 D

All

Ans. D

Explanation:

Ans. is ‘a’ i.e., Rickettsia; ‘b’ i.e., M leprae; ‘c’ i.e., Syphilis

Obligate intracellular organisms

.  To grow in a medium which does not contain cells (cell free medium), organism should be capable of ATP synthesis.

.  Obligate intracellular organisms are not capable of the metabolic pathways for ATP synthesis.

.  So, these organisms are dependent on the ATP of host cells.

.   As they require host cell ATP, they can not grow in the media which do not contain cells (cell free media).

.   Such organisms are ‑

1.  Rickettsiae                            

2. Viruses

3. Pathogenic treponemes (syphillis)

4. Chlamydiae

5. M. leprae


Q. 4

For experimental work, Lepra bacilli are best cultured in –

 A

Armadillos

 B

Mouse foot pad

 C

Guinea pigs

 D

Rabbit testes

Q. 4

For experimental work, Lepra bacilli are best cultured in –

 A

Armadillos

 B

Mouse foot pad

 C

Guinea pigs

 D

Rabbit testes

Ans. A

Explanation:

Ans. is ‘a’ i.e., Armadillos 

“It was found that armadillos infected with M. leprae often developed extensive disease, with up to 1010 bacilli in each gram of diseased tissue. This animal therefore provided sufficient bacilli for a number of studies and for the production of a skin test reagent, lepromin A”. –

“Limited replication, yielding 106 bacilli after 6-8 months, also occurs in the mouse footpad, and this has been used for testing the sensitivity of bacilli to antileprosy drugs” 

  • As M. leprae replicate extensively in armadilla (1010 bacilli/gram of tissue), while it has limited & slow replication in foot pad of mice, armadillo is best laboratory animal for cultivation of M. leprae.



Q. 5

True about lepra bacilli is –

 A

INH inhibits their growth

 B

Antileprosy vaccine can give life long protection

 C

Mycobacterium leprae can be grown in foot pad of mice

 D

Incubation period is 3-4 months

Q. 5

True about lepra bacilli is –

 A

INH inhibits their growth

 B

Antileprosy vaccine can give life long protection

 C

Mycobacterium leprae can be grown in foot pad of mice

 D

Incubation period is 3-4 months

Ans. C

Explanation:

Ans. is ‘c’ i.e., Mycobacterium leprae can be grown in foot pad of mice

.       Lepra bacilli can multiply in the footpads of mice kept at low temprature and this observation has become the standard procedure for experimental work with the bacillus.

About other options

.       Incubation period of leprosy is 3-5 years.

.       INH is not an antileprotic drug.

Leprosy vaccine

None of the candidate vaccines have yet attained as yet “vaccinehood”.

BCG vaccine seems to protect against leprosy because of some degree of antigenic relationship between lepra and tubercle bacilli. But no vaccine can give life long immunity.


Q. 6

Culture of lepra bacilli done in – 

 A

Nine banded armdillo

 B

Tail of mouse

 C

Foot pads of mice

 D

a and c 

Q. 6

Culture of lepra bacilli done in – 

 A

Nine banded armdillo

 B

Tail of mouse

 C

Foot pads of mice

 D

a and c 

Ans. D

Explanation:

Ans. is ‘a’ i.e., Nine banded armdillo; ‘c’ i.e., Foot pads of mice 


Q. 7

Lepra cells are –

 A

Neutrophils

 B

Lymphocytes

 C

Histiocytes

 D

Plasma cells

Q. 7

Lepra cells are –

 A

Neutrophils

 B

Lymphocytes

 C

Histiocytes

 D

Plasma cells

Ans. C

Explanation:

Ans. is ‘c’ i.e., Histocytes 


Q. 8

Generation time of lepra bacilli is – 

 A

12 days

 B

5 minutes

 C

10 hours

 D

24 hrs

Q. 8

Generation time of lepra bacilli is – 

 A

12 days

 B

5 minutes

 C

10 hours

 D

24 hrs

Ans. A

Explanation:

Ans. is ‘a’ i.e., 12 days 


Q. 9

Mycobacterium leprae can be cultured in:

September 2006

 A

Testes of guinea pig

 B

LJ medium

 C

Footpad of mice

 D

Testes of albino rats

Q. 9

Mycobacterium leprae can be cultured in:

September 2006

 A

Testes of guinea pig

 B

LJ medium

 C

Footpad of mice

 D

Testes of albino rats

Ans. C

Explanation:

Ans. C: Footpad of mice

In 1960 the American Charles Shepard discovered that it is possible to culture the bacterium in the footpads of mice (average 20 degree C).

In 1971 Waldeman Kirchheimer and Eleanor Storrs discovered that the nine-banded armadillo, Dasypus novemcinctus, could also become infected.

This species was selected because it has a low body temperature (approximately 34 degree C) and a primitive immune system.

The animal develops a generalised infection with involvement of the internal organs, especially the liver and spleen.



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