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Microbiology:Chapter 14

Mycobacterium leprae

01

Acid-fast rod

Impossible to grow on artificial media

(Grown in the foot pads of mice,

armadillos, and monkeys)

Nonmotile

Facultative intracellular growth

02

Catalase-positive

Grows best at low temperature

Phenolase-positive

Metabolism

03

Mycobacterium leprae causes leprosy,

also called Hansen's Disease.

04

- Infection occurs when a person is exposed

to the respiratory secretions or skin lesions

of an infected individual.

- Cell-mediated immunity (cellular immunity)

limits the spread of the bacteria. However,

it causes inflammation and granulomas.

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05

Leprosy damages the skin (sparing warm areas such as the armpit, groin, and perineum), the superficial nerves, eyes, nose, and testes

065 Subdivisions based on the level of cellular immunity

Lepromatous leprosy (LL)

Tuberculoid leprosy (TL)

Borderline lepromatous (BL)

Borderline (BB)

Borderline tuberculoid (BT)

Lepromatous leprosy (LL)Severest form of leprosy

- Patients with LL cannot mount a

delayed hypersensitivity reaction.

- Very low cellular immunity

Involves skin, nerves, eyes, and testes

Acid-fast bacilli are found everywhere

LL will lead to death if untreated

Tuberculoid leprosy (TL)

Milder and self-limiting disease - Patients with TL can mount a cell- mediated defense - Delayed hypersensitivity reaction is intact. - Patients demonstrate localized superficial, unilateral skin and nerve involvement; non-infectious and spontaneously recover.

Bacilli are difficult to find in lesions or blood

09BL, BB, and BT

Borderline lepromatous (BL). Borderline

(BB), and Borderline Tuberculoid (BT)

Represent a continuum between LL

and TL

** The skin lesions of BL will be more

numerous and have a greater diversity of shape than those of BT

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Tuberculoid Borderline Lepromatous

Number of skin lesions Single Several Many

Hair growth on skin lesions Absent Slightly

decreased Not affected

Sensation in lesions of the extremities

Completely lost Moderately lost Not affected

Acid-fast bacilli in skinscraping

None Several Innumerable

Lepromin skintest

Strongly positive No reaction No reaction

Spcectrum of Leprosy