Question
What is the generation time of the micro-organism which is marked by a black arrow in the photomicrograph below?
A. 2-5 days.
B. 7-10 days.
C. 12-14 days.
D. 20-25 days.
Show Answer
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Correct Answer » C
Explanation
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- The micro-organism shown in the photomicrograph above represents Mycobacterium leprae.
- Generation time of bacteria refers to the doubling time.
- Mycobacterium leprae is the slowest growing human bacterial pathogen, it has a doubling time of 14 days.
- It grows best at 30 degree C, at a temperature lower than body temperature, therefore it grows preferentially in the skin and superficial nerves.Mycobacterium leprae is transmitted by prolonged contact with patients with lepromatous leprosy, who discharge M. leprae in large numbers in nasal secretions and from skin lesions.
2 forms of leprosy are: Tuberculoid and Lepromatous.
- In tuberculoid type: CMI response to the organism limits its growth, very few acid-fast bacilli are seen, and granulomas containing giant cells form.
- In lepromatous leprosy: CMI response to organism is poor, the skin and mucous membrane lesions contain large numbers of organisms, foamy histiocytes rather than granulomas are found, and the lepromin skin test result is negative.
