Mycobacterial Diseases I Flashcards
One of the reasons people came to Colorado to treat tuberculosis is that ________________.
M. tuberculosis is an obligate aerobe and the lower oxygen content in Colorado prevents growth
All mycobacteria are _______________.
obligate aerobes
Mycobacteria are said to have a __________ coat.
“waxy” (from mycolic acid)
Where are mycolic acids in relation to the mycobacterial cell membrane?
They are attached to polysaccharides on the outside of the cell membrane.
How many people are killed by TB each year?
1.8 million (more than any other bacteria)
TB is the leading killer in people with _________.
HIV
Tuberculosis in the U.S. has been decreasing since ________.
1993 (there was a peak this year due to HIV)
How is TB transmitted?
Respiratory droplets quickly evaporate and become small enough to reach alveoli.
What percent of people exposed to TB develop infections?
30%
Of the people who develop TB infection, what percent go into latency?
95%
What molecule prevents fusion of phagosomes with lysosomes?
ManLAM
PIM induces ____________.
fusion of nutrient-rich endosomes with TB-containing phagosomes
One of the reasons TB induces granuloma formation is that _____________.
large, discrete lesions will cause the host to cough, thus spreading TB
What fraction of the Earth’s population has latent TB?
1/3
Why does M. tuberculosis cause cavitations?
The air allows the bacteria to grow.
___________ confers resistance to isoniazid.
katG (the catalase that activates the prodrug)
Importantly, Mycobacteria cannot acquire _____________.
genes by transformation –only through point mutations
Multiple studies have shown that ______________ is needed to eliminate TB.
a functioning immune system (that is, drugs alone cannot kill TB)
______________ should always make you think of reactivated TB.
Upper lobe lesions
Almost all facilities in the U.S. use _________ media because it is faster.
liquid
One of the problems of treating TB worldwide is that ______________.
traditional diagnostics (which rely on cultures and biochemistry techniques) take months to give precise susceptibility data
The strongest predictor of MDR TB is ____________.
past treatment for TB (with continuation or progression of symptoms)
What are the cutoffs for TST induration?
- High risk: greater than 5 mm
- Intermediate risk: greater than 10 mm
- Low risk: greater than 15 mm
Why does M. tuberculosis reactivate in the upper lobes?
Those are more aerated, and M. tuberculosis is an obligate aerobe.
M. tuberculosis is highly durable because _______________.
of its mycolic acids that prevent desiccation and protect from disinfectants
Cultures used to isolate M. tuberculosis are mixed with __________, which selectively kills most other bacteria.
alkali
Although Mycobacteria are neither Gram-positive nor Gram-negative, they are more similar to _____________.
Gram-negative, because the mycolic acid layer has an outer membrane just like the peptidoglycan layer has an outer membrane in Gram-negative bacteria
The initial TB infection is usually just ____________.
an influenza-like illness
What is the primary immune response to M. tuberculosis?
Cell-mediated
Note: humoral immunity has no role in the elimination of or protection from tuberculosis.
How does miliary TB develop?
In individuals with deficient macrophage response, the primary infection is not able to controlled and the bacilli are able to spread throughout the body.
True or false: most of the symptoms of TB are the result of endotoxin.
False. The symptoms of TB are predominately from the immune response.
How does the newer screening test for TB work?
You place patient blood in an incubator with proteins only found in M. tuberculosis (not in M. bovis –hence, it can differentiate between BCG and exposure) and measure the amount of IFN-gamma released overnight.
Which mycobacterium is hardest to kill?
M. abscessurs
Hypopigmented, anesthetic skin patches are characteristic of ________________.
M. leprae infection
Describe high-risk and intermediate-risk for TB.
• High-risk:
- HIV
- Recent past infection
- Recent immigrants from endemic areas
- IV drug users
- Immunosuppression
•Intermediate-risk:
- Healthcare workers
- Known contact with infected person
True or false: TB is never fully eliminated, even with robust treatment.
False. About 95% of cases are full cures.
Who is a candidate for treatment of LTBI?
Those with positive IGRAs or TSTs who have normal chest x-rays
(Abnormal x-rays prompt evaluation for active TB.)
Non-tubercular mycobacteria tend to prefer ____________ climates.
warmer (except M. leprae)
What organism causes Buruli ulcers?
M. ulcerans
M. leprae preferentially affects the ______________.
skin, eyes, and mucosa of the URT
