Lower Respiratory Tract Infections (LRTIs) Flashcards
What microorganism causes tuberculosis?
Mycobacterium tuberculosis (MTB)
Describe the morphology of MTB
Bacillus, non-motile, acid fast (no G), obligate aerobe
What does MTB produce that causes bacteria to clump + inhibits phagocytosis?
Cord factor
Does MTB produce toxin?
No
What forms an impermeable barrier around MTB?
Mycolic acid
What is the major pathogenic mechanism of MTB?
Inflammation
How is TB transmitted?
Airborne
What are the 3 outcomes after TB?
- Latent infection
- Primary tubercle forms
- Spread of active infection
Describe latent infection
TB enters macrophages and remain
Describe primary infection
Host cell isolates the infection in a tubercle (granuloma)
Why can’t TB replicate inside tubercles?
Low pH + low oxygen
When does a disseminated infection (miliary tuberculosis) occur?
If tubercle doesn’t form or if it ruptures
Describe second stage infection
Spread of tubercles from primary infection or reactivation of latent infection
Is MTB present in both TB latent infection and active disease?
Yes
What are the results of a Tuberculin Skin Test for TB latent infection and active disease?
Latent: positive
Active: negative
Describe chest x-ray results for TB latent infection and active disease
Latent: normal
Active: reveals lesion
What are the results of a sputum smear & culture for TB latent infection and active disease?
Latent: negative
Active: positive
Describe the symptoms of TB latent infection and active disease
Latent: none
Active: cough, fever, weight loss
Are TB latent infection and active disease infectious?
Latent: no
Active: infectious before treatment
Are both TB latent infection and active disease defined as cases of TB?
Latent: no
Active: yes
What are the 6 methods of diagnosing TB?
- Acid-fast rods in sputum
- Culture
- QuantiFERON Gold
- Skin test
- Tuberculin test
- Mantoux test