CA - Tuberculosis (CKL) Wk 4 Flashcards
What is the main mode of Mycobacterium Tuberculosis (MTB) transmission?
- Human-to-human
- inhalation of droplets, coughing, sneezing, talking
- must be PROLONGED exposure
What is the diagnostic test for TB? Why?
Why cant Gram stain microscopy be used?
MC&S
Microscopy (Acid Fast Bacilli stain)
Culture and sensitivity
Why cant Gram stain microscopy be used?
- waxy lipid outer wall prevents effective staining using Gram stain technique
What does sputum AFB smear positive & negative mean?
(+): more infectious, has AFB seen under microscope
(-): less infectious
Who are at increased risk of Mycobacterium Tuberculosis (MTB)? (10)
- Intense exposure
- Immigrants from developing countries
- Malnutrition
- Alcoholics
- Homeless
- IV drug abusers
- Prison inmates
- Elderly, very young
- HIV pts
- Immunocompromised
How does TB spread and which parts of the body does TB spread to?
- Lump of infected macrophages + TB can travel to diff parts of the body by the lymphatic system or blood
- Degenerating cells at site -> pneumonitis (unusual) = inflammation & infection of lung cells
- Lymphatic circulation - to regional lymph nodes:
- hilar
- mediastinal
- supraclavicular
- retroperitoneal (within abdomen) - Non-immune / infants
Haematogenous/bloodstream spread
- lymph nodes
- kidney -> has rich blood supply
- bones / vertebral body -> travels to bone marrow
- meninges
- apical-posterior part (apex) of the lungs -> TB prefer more o2 env & lung apex has more o2
Why is a good granuloma formation important?
- just undst: its a result of the degree of hypersensitivity (determines whether granuloma is formed well or not) & local concentration of antigens
- small antigen load = small amt of MTB antigens present in body
- Prevents overwhelming immune activation & tissue destruction. - high tissue sensitivity = organisation of immune cells -> well-formed granuloma
- encapsulates & contains infection
- alive but latent TB inside -> non progressive
How does a poor granuloma formation affect the infection?
- Poor organisation & formation of immune cells -> caseating (cheesy) granuloma -> TB & pus leak out -> spread to other parts of body
What is LTB and what are the symptoms of Latent TB Infection ?
- Person is infected with TB before but body can contain infection
- No external signs of infection and are well
- Asymptomatic and non-infectious
How do we test for LBTI? (3)
- NO gold standard test
- ONLY for LBTI
- TST (tuberculin skin test)
- IGRA (Gamma Inteferon (IFN-gamma) Release Assay) (more accurate)
Why are the tests used for LBTI not gold standard tests?
Neither can differentiate between active and latent TB infection
Is active TB symptomatic & infectious?
YES & YES
What is the specimen type for active TB?
- Early morning sputum - At least 2, usually 3 specimens
- give time for TB to settle in lungs overnight & can be expelled in the morning - If TB in other site, send respective sample
- AFB stain for TB
What is the time taken for TB culture?
- 15-20 hours to replicate
(common bacteria <1 hour) - culture incubate for 6-8 weeks
(common bacteria 2-5 days)
What can PCR test for and how long does it take?
- Is it TB or not?
- Is it multi-drug resistance TB or not? -> ensures that the right drug is given
- Get results in 1 day!!!
How can we prevent TB?
- BCG - Live attenuated vaccine, cannot give immunocompromised
- Does not prevent infection, but prevents progression to clinical disease & prevents miliary TB in children
Why is TB a public health concern?
- Case finding & treatment is crucial for TB
- Hospitalised pts with suspected TB should be placed in (-) pressure isolation room
- HCPS should wear N95 masks
Whats the difference between Non-tuberculosis Mycobacterium (NTM) & Mycobacteria tuberculosis (MTB)?
NTM
- can be gotten from the env (tree, soil, water)
- not spread from person to person
MTB
- public health infection
- ONLY spread from person to person
What is quiescent infection? (DN TO KNOW)
- Latent TB
- Body able to contain TB without leading to active infection
- Infection controlled in non-replicating form
What is miliary TB? (dn to know - js read)
- Disseminated TB in blood stream
- TB goes to many parts of body via bloodstream persistently
- High chance of death in neonates (TB meningitis)
- Can occur in immunocompromised or children
- Appears as little dots full of TB
How is a patient with TB managed? (DN to know)
- Isolate patient
- Empirical treatment if TB is suspected (Rifampicin, Isoniazid, Pyrazinamide, Ethambutol) before C&S arrive as results take weeks
- give combination of abx: targets rapidly growing & dormant TB
When is a TB patient no longer infectious? (DN TO KNOW)
- Generally after 2 weeks of effective treatment in drug-sensitive TB
- 3 consecutive AFB smear-negative specimens
- Clinical signs improve
Whats the usual duration of treatment for active TB? (DN TO KNOW)
- 6mths at least
- drug concentration has to be at a certain level to kill TB -> if dose is missed abx level will decrease -> TB can mutate -> drug resistance
