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24 Cards in this Set

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What are the major species of Mycobacterium? Nocardia?
M. tuberculosis
M. avium/intracellulare
M. leprae

N. asteroides
What are the morphological characteristics of M. tuberculosis?
Weakly-staining gram positive rod, growing in cords. Intracellular pathogen.
What's the best way to visualize MTB?
Acid-fast stain (Ziehl-Neelsen).
What are the environmental reservoirs for MTB?
None - humans are the only hosts.
Diffuse pulmonary MTB infection is called...
Miliary Tuberculosis
Are PPD tests entirely sensitive for TB infection?
No - ICZ/HIV-AIDS patients may not develop a delayed-hypersensitivity to subq PPD injections, leading to a false negative reading.
When I say MTB Granuloma, you say...
Caseating necrosis
What is the route of infection for MTB?
Horizontal transmission via respiratory droplets.
How is an active MTB infection diagnosed?
* Clinical suspicion (low-grade fever, night sweats, weight loss, chronic cough)
* CXR
* Acid-fast sputum stain
* Catalase POSITIVE
Who is credited for the first description of MTB?
Robert Koch, in 1882 (Nobel in 1905)
What special component is found in the cell wall of MTB?
Mycolic acid
What is problematic about MTB Tx?
Organisms quickly develop resistance - multi-drug regimens required for active TB
What's the morphologic characteristics for Mycobacterium leprae?
Weak-staining gram positive, acid-fast, intracellular bacillus
In what two cells does M. leprae grow?
Schwann cells and macrophages
In what two syndromes does M. leprae present?
Lepromatous and tuberculoid
What characterizes a Lepromatous leprosy?
Strong humoral and weak cell-mediated response, i.e. TH-2 (ineffective, as pathogens reside intracellularly)
How is leprosy diagnosed?
Clinical suspicion. AFB on tissue biopsy, granuloma. Lepromin skin test.
What two major bacteria comprise the non-tuberculous mycobacteria?
M. avium-intracellulare complex (MAC)
M. marinum
How does non-tuberculous mycobacteria present in a healthy host? In ICZ/HIV?
Healthy: Lymphadenopathy
ICZ: important source of disseminated infection, pneumonia,
What's the popular term for M. marinum lesion?
Swimming pool granuloma
What's the morphologic characteristics of Nociardia asteroides?
Gram positive, Acid Fast filamentous branching rods.
What is the main clinical disease caused by N. asteroides?
Bronchopneumonia, caused by inhalation of aerosolized organisms.
What complications may develop from a N. asteroides infection?
Metastatic disease to CNS. If recent PNM and focal Sx suggest CNS, think Nocardia...
Is there a cutaneous Nocardia infection?
Nocardia brasiliensis - pustule, fever, lymphadenitis