Mycobacteria Flashcards
What are the features of the Genus mycobacteria?
- ZN stain -acid-fast
- non-spore forming
- non-motile
- slow growing
Why does mycobacteria require specimen homogenization?
They are slow growing, thus requires decontamination step to kill other bacteria first before culturing using NaOH
How can we distinguish M. tuberculosis from M. leprae?
M. tuberculosis is heat-sensitive catalase +ve
State the transmission of M. tuberculosis.
Air borne
Pathogenesis of M. tuberculosis depends on host immunity. Briefly explain why.
- Host immunity +ve: no disease, chronic inflammation (granuloma with central necrosis, bacteria dormant but viable)
- Host immunive -ve: reactivation, present in any organ
Which of the following about M. Tuberculosis is correct?
A. it is facultative intracellular, which persists in macrophages
B. it is an obligate aerobe
C. It can spread from lungs to hilar LN and even other organs via blood
D. It can be grown quickly on LJ medium
E. Tuberculin test- PPD 2TU ID is used as diagnosis, zone of skin induration is measured.
All except D
- Acid fast bacteria culture: LJ medium, but slow-growing (4-6 weeks), faster with radiometric substrate
List the possible symptoms of primary pulmonary TB.
- Asymptomatic
- Constitutional Sx (fever, night sweats, fatigue, weight loss)
- Pulmonary Sx (cough, sputum, hemoptysis)
What does it mean by secondary pulmonary TB?
Due to temporary weakening of CMI (cell-mediated immunity), it may disseminate to any other organs (miliary TB) with poor prognosis
What is tuberculoma?
- Tuberculoma/ Tuberculous meningitis: CNS cavity lesion
What are the possible manesfistations of secondary TB in lymphatics?
- Tuberculosis lymphadenitis (scrofula): MC non-pulmonary TB, usually involves cervical LN
- TB peritonitis: due to rupture of caseous abdominal LN
What is the disease related to skeletal system in secondary pulmonary TB? Which part of the skeletal system is damaged?
Pott’s disease affected thoracic and lumbar spine (demineralization vertebral bodies)
What can be the treatment for M. tuberculosis infection?
RIPE: R: rifampin I: Isoniazid P: Pyrazinamide 先啊咪 E: Ethambutol
What are the preventive medicine for M. tuberculosis?
- BCG vaccine
- Rifampicin and isoniazid for latent TB
Which of the following about M.leprae are correct?
A. It is an obligate intracellular
B.It’s optimal growth is similar to human body temperature
C. It is transmitted by nasal discharge or prolonged contact
D. It’s pathogenesis involve peripheral nerves more than central nerves
All except B
B: should be less than body temperature (27-30 degrees)
D: Cooler parts of the body - skin, peripheral nerves, extremities
What are the test results (2 forms of leprosy) of M. leprae in Lepromin skin test ?
+ve in tuberculoid form
-ve in lepromatous form
What are the 2 forms of leprosy and what are their differences in terms of CMI?
- Tubercoloid (TL)
- Strong, Th1 mediated - Lepromatous (LL)
- weak Th2 mediated
What are the differences between tuberculoid and lepromatous leprosy in terms of
- Organism in tissue
- Damage origin
- Treatment duration
- Hypopigmentation
TL
- Low amount of organism in tissue
- damage origin is CMI > non-ceseasting granuloma formation
- Treatment: 6 months
- marked hypopigmentation
LL
- high amount of organism in tissue
- damage origin: overgrowth of bacteria
- Treatment: more than 2 years
- little hypopigmentation
What are the characteristic clinincal charateristics in both TL and LL together? (4)
- Nerve: sensory loss, paralysis
- Skin: thickening, nodular appearance, leonine facies
- Bone: resorption and shortening of digits
- Muscle wasting
What are the treatment for leprosy?
- Dapsone
- Rifampin
(+3. clofazimine for LL)
How is Mycobacteria other than tuberculosis (MOTT) classified?
Runyon group: classified bsed on ability to produce pigment and growth rate
- it is non-contagious
M. avium complex (MAC) and M.kansasii are commonly presented in which types of patient?
- with pre-existing pulmonary diease
2. immunocompromised patients
Which types of MOTT are associaed with bone/joint/soft tissue infection after trauma?
M. fortuitum and 課頹tum
M. chelonae “ke”攞黎
Which type of MOTT causes pulmonary infection which is clinically indistinguishible from TB but not airborne transmitted?
MAC (M.avium complex) and M. kansasii
What disease is M. scrofulaceum associated with?
Cervical lymphadenitis (scrofula) in children
What diseases is M. marinum associated with?
Superficial skin lesions - fisherman’s granuloma
