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14 - Pathology: Myobacteria


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Do Mycobacteria produce toxins?
2 ways in which Mycobacteria damage the host

Hypersensitivity response (DTH = Type 4)
Agent that causes TB
Mycobacterium tuberculosis Homonis (Koch's Bacillus)
Other name for Mycobacterium Leprae
Hansen's Bacillus
Trasmission route of TB
DROPLET (larger than aerosols)
Mycobacterium TB is resistant to ________

*surfaces must be disinfected to prevent spread
Total cases of TB worldwide
88 M
Portion of the world infected with TB
# of TB deaths annually
1-3 M

*highest mortality for any infectious disease
When did TB rates in US climb?
1985 with the rise of MDR strains and AIDS
Doubling time for TB
24 hours
How long are cultures kept before being declared negative?
6 weeks

*6 months with solid media
Modern laboratories should be using ______ media to decrease incubation times
Modern laboratories should be capable of doing a sputum smear for ______ within 4 hours
Acid-fast bacteria
Solid media for TB
Lowenstein-Jenson media
Immunofluorescent stain for TB
Colony morphology of TB

Bread crumb look
TB liquid growth media
Virulence factor that causes TB to stick together

Cord Factor
Primary TB characteristics
Self-limited in 95% of cases
Ghon Complex
What is a Ghon Complex
Granuloma in the upper Lung and Mediastinal (hilar) Lymph Node
Progressive Primary TB only occcurs in these 2 groups of people
IC'ed Adults

Children -> TB meningitis
Secondary Miliary spread via a Pulmonary Vein results in...
organisms return to the left ventricle and pumped throughout the body
Secondary Miliary spread via Pulmonary ARTERY results in...

spread within the lung
What to look for when reading PPD skin test
Vaccine used for TB
BCG vaccine = live attenuated
Why is BCG not used in US?
because TB clinical symptoms is rare in US and we want to be able to test for exposure
BCG's only clinical use in the US
used for treating Bladder Cancer
What does TB do to the brain?
TB Meningitis can obstruct the flow of CSF leading the Hydrocephalus
Site of brain most often affected by TB
Base where CN are located
2 ways of getting GI tuberculosis
1. swallowing expectorated TB from lungs
2. M. bovis ingested via contaminated milk
Most common agent of Mycobacterial Entercolitis
M. Avium Intracellulare
GI MAI almost occurs exclusively in these people
Late stage HIV
1st bacterium ever discovered
M. leprae
2 clinical forms of Leprosy
1. Lepromatous (worse)

2. Tuberculoid
M. leprae prefers these areas of body
cooler areas of skin, such as face and extremities
Transmission of M. leprae
PROLONGED, close contact
Animal M. leprae is found in
M. leprae cannot be cultivated on...

Can be cultivated on...
artificial media

Mouse foot-pads
Accurate diagnosis of leprosy relies on....
skin biopsy that is compatible with the clinical picture
Mycobacterium Avium Intracellulare primarily causes a disseminated disease in ________
IC'ed hosts
MAI can cause this disease in normal hosts
Chronic lung disease
CD4 count when MAI usually infects
MAI colony morphology

2 cases where M. kansasii may present
1. old person with pre-existing lung disease

2. young person with HIV

What mircobe is this?
Mycobacterium Avium Intracellulare

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