Mycobacteria Flashcards
What is the main acid-fast genus of bacteria?
Mycobacteria
What is the gram stain of mycobacteria?
gram +
What is the O2 requirements of mycobacteria?
Obligate aerobe
Koch identified ________ as cause of TB in 1882:•Humans are reservoir•airborne transmission (as few as 10 cells can result in infection)
Mycobacterium tuberculosis
Koch identified Mycobacterium tuberculosis as cause of TB in 1882:• ______ are reservoir
•airborne transmission (as few as 10 cells can result in infection)
Humans
Koch identified Mycobacterium tuberculosis as cause of TB in 1882:
• Humans are reservoir
•______ transmission (as few as 10 cells can result in infection)
airborne
Mycolic acids in cell wall
Gram+weak staining: use acid-fast stain or specific fluorescent detection
Facultative intracellular growth(in macrophages)
Obligate aerobe (growth in lung macrophages)
Mycobacteria
What stain is used to distinguish mycobacteria
Acid fast stain
What is the chemical composition of the cord factor within the mycobacterial cell wall?
glyco-lipid
Slow, cord-like growth
strongly correlates
with virulence.
Cord-like growth results from adherence of cell surface lipid mycolic acids and glyco-lipids
virulence factors of mycobacteria
While many “virulence factors” are listed, their virulence results from the challenge that they provide to the _____ _____ (typically DTH: CD4+ T-cells + macrophages)
because (in most cases) the disease is caused by the immune response, NOT by the mycobacteria.
immune response
Facultative intracellular growth in alveolar and other macrophages:
inhibition of phago-lysosome fusion
virulence factor of M.tuberculosis and M.leprae
_______ _______ is a “life-long” pathogen: once infected, you may be asymptomatic but never cured.
Mycobacterium tuberculosis
the _____ area of the necrosis is where the ______ have been destroyed.
central
nuclei
Effective CMI is capable of localizing and stopping infection by M.tuberculosis. Chronic TB is
typical.
What is the exception????
Exception: young children under 5 years have a high risk for developing progressive TB due
to insufficient immune system development/activation.
- 91% no disease
- 6% clinical TB (2% pulmonary + 3% extrathoracic + 1% both)
- 3% progressive systemic disease and death.
OUTCOMES of untreated primary TB [results for non-immune-compromised patents]:
However, ______ (‘open’) TB [also known as “secondary tuberculosis” or in older terms
“galloping consumption” caused by “endogenous reactivation” of prior infection
- while rare (life-time risk is assessed as <12% for carriers, or less) it is VERY contagious!
Isolation of acute TB cases is mandatory. Endogenous reactivation is stimulated by stress, malnutrition and HIV
acute
T/f: concerning Mycobacterium tuberculosis, the “disease” (except for the infection risk of “Open TB”) arises from tissue destruction
by our immune defenses and not by damage caused by the bacterial infection.
true
t/f: The repeated attempts to remove foci of infection by lung macrophages cause the granulomatous
lung tissue that impairs lung function.
true
t/f: Breathing impairment in TB is not due to tuberculosis bacilli but by the macrophage-induced tissue
destruction
true
A positive tuberculin test to subdermal PPD (processed protein derivative of the cell wall of the opportunistic intracellular pathogen M ycobacterial tuberculosis).
Mantoux Reaction
with the Mantoux Reaction test, a >10mm redness indicates _______ while a >20 mm redness indicates ______.
positive test
strong positive
Exposure to living attenuated mycobacterium, known as Bacille Calmette-Guérin (BCG), a derivative of M.bovis (which may be identical to M.tuberculosis based on whole genome sequencing):
- little virulence in humans (but infectious in immune-compromised persons)
- some protective immunity (when given to young children)
- BCG vaccination is discouraged in USA because it gives a positive tuberculin test, thus removing an important diagnostic screening tool. (And M.bovis causes disease in immune-compromised persons.)
m. tuberculosis vaccine
macrophages kill nerves; macules and plaques without sensation
Good prognosis for recovery NOT infectious
Th1-response
Bad prognosis for recovery Highly infectious
Loss of CMI (CTL lysis and loss of tissue including nerves)
Th 2-response
Dapsone + rifampin + clofazimine
Rising resistance is becoming a problem.
Multi-drug therapy
virulence factor of ____ ____
ability to survive and live in lung macrophages
m. Tuberculosis
clinical factor of ____ _____:
pulmonary and extrapulmonary tuberculosis.
m. Tuberculosis
treatment of _____ ____:
multidrug therapy (6-12 months)
m. Tuberculosis
epidemiology of ____ ____:
aerosol (person to person)
all ages
highest risk if : immune compromised (HIV)
m. Tuberculosis
virulence factor of ____ ____
ability to survive and live in macrophages
M. Leprae
clinical factor of ____ _____:
tuberculoid to lepramatous leprosy
M. Leprae
treatment of _____ ____:
multidrug therapy (2 years)
M. Leprae
epidemiology of ____ ____:
close physical contact
M. Leprae
t/f: All pathogenic mycobacterial species have (very) slow growth rates
true
Gram+ (poor staining)
• mycolic acid in cell wall: “partially acid-fast”
(Test to distinguish Nocardia from fungal look-alikes)
Opportunistic pathogen
in immuno-compromised patients
nocardia
