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08.Medical Microbio - TB
Finished
32
Biology
Graduate
12/15/2008

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Term
Tuberculosis Global Incidence
Definition
kills about 1.7 million people per year
 
about 1/3 of the world is infected w/ TB
 
People w/ HIV are at much higher risk
Term
multi-drug resistance TB
Definition
TB that fails to respond to standard first line drubs
Term
Extensively drug resistant TB
Definition
occurs when there is resistance to first AND second line drugs
Term
TB in Canada
Definition

highest in Nunavut

Lowest on the East coast

Term
Mycobacteria
Definition

aerobic, non-motile bacilli

Are Acid fast

 

include:

 

Mycobacterium tuberculosis and mycobacterium leprae

Term
MOTTS
Definition

Mycobacterium Other Than Tuberculosis

 

-resp. for opportunistic infections, esp. w/ AIDS patients

Term
Acid Fast Stain
Definition

Used to determine the presence of TB

 

dye w/ red stain carbolfushin

put HCl and alchohol over

 

*If red remains, then it is acid fast b/c mycobacterium cell walls to not dissolve w/ acid alcohol.

 

 

Term
What makes mycobacterium acid fast?
Definition

due to thick layer of mycolate (mycolic acid) on the outside

 

 

mycolic acid is an important virulence factor

Term
cording
Definition
When grown on agar, colonies of virulent strains attache to each other by rope like cords
Term
Sulfatides
Definition

myscosides w/ sulphates attached

inhibit phagasomes (which protects M. tuberculosis)

Term
Wax D
Definition
complicated mycoside that activates the cellular immune system
Term
Transmission of TB
Definition

-occurs via the inhalation of droplet nuclei (released by coughing/sneezing)

 

-infected patients can have as many as 105 - 107 bacilli/mL

Term
Body's fight against TB
Definition
macrophages - kill mycobacterium
                      -However, can provide niche for th
                       bacteria to multiply w/i
 
denditic cells - engulfs bacteria
 
T-cells -  release cytokines w/ enhance macrophages
Term
Primary progressive disease
Definition

aka. Primary Tuberculosis

 

If t-cell response in insufficient in controlling TB, clinical symptoms will develop w/i a year.

 

Usually occurs amoung young children and immuno-comprimised persons.

Term
Latent TB Infection
Definition
-occurs in most individuals
 
-T-cell response is mounted, and no clinical symptoms occur
 
However, there is the risk of secondary TB because the bacteria can persist w/i granulomas
Term
Vaccine to help establish T-cell numbers
Definition
live Bacille Calmette - Guerin
Term
Secondary Tuberculosis
Definition
Dormant bacilli become reactivated after years
Term
Stage I of pulmonary tubercuosis
Definition
-inhalation of bacilli, which are ingested by macrophages
 
-90% of bacilli are destroyed by macrophages, however, remaining 10% evade the host's defense by hiding in the macrophages
Term
Stage II of tuberculosis
Definition
-Bacilli w/i macrophages multiply and are released upon macrophage death
 
-bacilli attract monocytes and macrophages and forms and tubercle 
 
-bacilli multiply within the cytoplasm of unactivated macrophages
 
-both bacilli and macrophages are increasing, and neither is being destroyed during this phase=symbiosis
Term
stage III of TB
Definition
-2-3 weeks after infection get delayed
   hypersensitivity and cellular immunity
 
-delayed hypersensitivity halts the logarithmic growth by killing bacilli-laden macrophages
 
-results in caseous necrotic center of dead and live bacilli in the tubercle
 
-bacteria w/i necrotic center cannot multiply
 
 
Term
Stage IV of TB
Definition
two options:
 
Weak cell mediated immunity
    -caseous center enlarges, lung tissue destroyed,
     bacteria is released and ingested by unactivated
     macrophages.
 
Strong cell mediated immunity
    -bacilli released from caseous center, ingested by
     activated macrophages with little tissue
     destruction.  Occurs in 90% of cases.
Term
Stage V of TB
Definition
-liquefaction of the solid caseous focus
 
-bacilli multiply extracellularly, extensive tissue damage
 
-Spread of bacilli via the bronchial tree to other parts of the lungs often leads to tuberculous pneumonia.
Term
PPD Test
Definition
Purified Protein Derivative Test
 
-PPD injected intradermally
 
-macrophages in skin take it up
 
-induration of >10mm after 2 days suggests TB expo.
-induration of >5mm in AIDS patients suggests TB
 exposure.
Term
Symptoms of TB
Definition
-weight loss
-low grade fever
-productive cough
-night sweats
-calcified tubercles in middle-lower lung region
Term
Extra pulmonary tuberculosis
Definition
-affect lymph nodes, pleua, gentiourinary tract, etc
 
-pretty much any organ system can be affected
Term
TB rule of '5'
Definition
-droplet nuclei are 5 micrometers (and contain 5 bacilli)
 
-Patients w/ TB have a 5% risk of reactivation w/i first 2 years, and 5% risk life long
 
-HIV patients have a 5+5% change of reactivation each year.
Term
Mycobacterium Avium
Definition
-usually infects birds
-found in over 50% of AIDS patients
 
-Infects when helper T-cell levels are virtually nil
Term
TB Diagnosis
Definition

-PPD test

-Chest xray (for calcified tuburcles)

-acid fast test on sputum

-Culture

Term
First line of Anti-TB drugs
Definition
Insert clever mnemonic here.....
 
 
Isoniazid
Rifampin
Pyrazinamide
Ethambutol
Streptomycin
I Read Poetry Every Sunday
Term
Important principles of TB treatment
Definition
-administer multiple drugs at a time
-in cases of failure, add at least 2 new drugs
 
Term
Length of TB Treatment
Definition
6-9 months with drug combo
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