Mycobacterium Flashcards
(32 cards)
How long does it take to grow TB on a plate?
3-6 weeks for primary isolation
All are aerobes
Hallmark of TB stain
Acid fast staining
- 60% lipid (most are 15%) so it takes up stain easily, but cant get rid of it
Which bacteria results in the most deaths?
M.TB
Transmission of TB
Aerosol
- respiratory droplet nuclei
- small particles capable of reaching alveolus
How many people exposed to TB will result in an infxn?
How of those with a TB infxn will progress to primary disease?
How many of those that contain the TB infxn will result in reactivation?
30%
- due to inadequate non-immunologic defense
5% of 30%
- due to inadequate immunologic defense
5% of the 95% that was contained will reactivate
- due to inadequate immunologic defense.
TB replicates in macrophages, where do they get carried to?
draining lymp nodes –> blood –> other organs
What confers resistance to INH?
Down regulation of katG
*katG (bacterial catalase peroxidase)- normally activates INH
When are individuals who are recently infected, most prone to progressing?
1-2 yrs
classic pattern of reactivated (post primary) TB
Upper lobes
High risk conditions for TB
High risk:
- HIV
- close contact
- recently infected
- abnl chest x ray
Intermediate risk:
- Transplant or immunosuppression
- Medical conditions
- Injection drug users
- . Recent arrivals from endemic contries
Risk for new infxn
- Contacts to infxn diseases
- Health care workers
- Other workers exposed to TB cases
Pulmonary sx of TB
- COugh >3 weeks
- Chest pain
- Hemoptysis
Systemic:
- Fever
- Chills
- Night sweats
- Appetite loss
- Weight loss
diagnostic work up of TB
- 3x Sputum sample –> AFB (acid fast bacillus) smear
- Mycobacterial culture
- Species ID
- Drug susceptibility testing
What do you suspect if TB is resistant to Rifampin?
most likely multi drug resistant TB
Tx of TB
4 for 2 months
2 for 4 months
If you have no risk for TB, how many mm does it have to be to be considered positive on PPD?
What about if you are a child?
Immunosuppressed?
> 15 mm
Child: >10
Immunosuppressed: 5mm
Quantiferon IT
3 antigens
Draw 3 tubes of blood
Put an antigen into each tube (- control, + control, Ag)
- measure serum gamma interferon [ ] if Pos = TB
TSPOT TB
Use 2 antigens
Stimulate lymphocyte over night and observe plate
- each spot is a lymphocyte producing interferon
8 or more = Pos test
What test is best done on BCG vaccinated indiv?
Interferon Gamma release assays (IGRAs)
- high specificity
Shortest drug regimen for TB
Isoniazid and rifapentine
- longer half life
- 3 months (not 4 with RIF)
- less hepatotoxic
1 killer of AIDS pts
M.Tb
Nontuberculous Mycobacteria
Exposed to them a lot
Not transmissible fr hu to hu
- VERY resistant to Ab
Most common sx is in the lung
Which state has the most NTM ?
Hawaii
Cali
Florida
- hot and humid
- people moving there already having dz (arizona)
Lady wyndamere syndrome
Tall, Skinny women more likely to get TB
*named after play: Women may be suppressing their coughs
