Exam 3 (Mycobacteria) Flashcards
Mycobacteria: Gram: Stain: Preferred growth medium: O2 req:
Gram: G+
Stain: acid-fast or fluorescence
Growth: facultative intracellular (macrophages)
O2 req: obligate aerobe (lung macrophages)
What is the main reservoir for mycobacterium and how are they spread? How many cells for infection?
- humans
- airborne transmission
- little as 10 cells
The _________________ step of acid fast staining drives the red dye into cells with _________ in their cell membranes.
- hot carbol fuscin
- mycolic acid
What is cord factor? What cells is it found on? What kind of molecule is it?
A glyco-lipid found on mycobacterium that is associated with mycolic acid. Assists in cell-cell adhesion and helps with “cord-like” growth of these cells.
_________ and __________ facilitate the slow ________ growth in mycobacterium that strongly correlates with virulence.
- Cord-factor
- mycolic acid
- cord-like
What is unique about immune responses to mycobacterium? What immune cells are involved?
- virulence of M. tuberculosis and M. leprae trigger immune response that causes the disease.
- CD4+ T-cells and macrophages
How do mycobacterium survive in macrophages?
inhibition of phago-lysosome fusion
What are the two characteristics of a tubercle caused by TB?
- granuloma surrounded by punctate nuclei of lung tissue and inflammatory leukocytes
- centra area of necrosis where nuclei have been destroyed
T or F:
Once a pt is asymptomatic with TB, they are considered cured.
FALSE
-life-long disease, once infected can be asymptomatic but never cured
What age group has a high risk of developing progressive TB?
children under 5 years
Outcomes of untreated TB:
- ___% no disease
- ___% clinical TB
- ___% progressive systemic disease and death
- 91% no disease
- 6% clinical TB (2 pulm, 3 extrathoracic, 1 both)
- 3% progressive sys dis and death
What form of TB is most contagious? What causes it?
- Secondary Tuberculosis
- caused by endogenous reactivation of prior infection stimulated by stress, malnutrition, and HIV
What is a Mantoux Reaction? What triggers it?
- positive tuberculin test
- triggered by subdermal PPD (processed protein derivative of cell wall of M. tuberculosis)
+: >10mm redness
strong+: >20mm redness
What is BCG and why is is not used in the US?
Bacille Calmette-Guerin is derivative of M. bovis. Used for vaccination against TB.
-discouraged in US because it gives positive TB test and is infectious in immunocompromised pts
What is isoniazid?
effective chemotherapeutic agent against TB
What are the three main CMI outcomes of M. leprae?
- HEALTHY: Effective CMI = healthy
- TUBERCULOID: TH1-response = macrophages kill nerves, macules and plaques without sensation
- LEPROMATOUS: bag prognosis for recovery, highly infectious
What happens in a TH2 response to TB?
-cytotoxic T-cell lysis and loss of tissue including nerves
What multidrug therapy is effective against Leprosy?
Dapsone + Rifampin + Clofazimine (rising resistance is becoming a problem)
All pathogenic mycobacterial species have ____________.
slow growth rates
Difference in clinical features and Tx of M. tuberculosis vs M. leprae?
TB-
Clinical features: pulmonary and extrapulmonary tb
Tx: multidrug therapy for 6-12 months
Leprosy-
Clinical features: tuberculoid-to-lepramatous leprosy
Tx: multidrug therapy for 2+ years
Epidemiology of M. tuberculosis?
- aerosol
- all ages
- highest risk to immune compromised
Epidemiology of M. leprae?
-close physical contact
Gram type of Nocardia?
G+ (poor staining)
What is notable about the staining technique needed for Nocardia?
mycolic acid in cell wall allows for acid-fast staining to differentiate from fungal look-alikes
Nocardia is an ________________ for _________ patients.
- opportunistic
- immunocompromised
