Infectious Diseases: TB

Question 1

Outline the pathophysiology of TB

Answer 1

Transmission = respiratory droplet - coughing, sneezing

Inhaled infectious droplets —> engulfed by alveolar macrophage —> local LN —> primary complex —> 1) PRIMARY - active disease, 2) LATENT = 95% self-cure, 5% reactivated into post primary TB

Miliary = disseminated through bloodstream

Latent = inactive, TST/IFN +ve, CXR normal, cultures -ve, asymp, not infectious

TB disease = active, TST/IFN +ve, CXR abnormal, cultures +ve, symptoms, infectious

Question 2

Outline the aetiology of TB.

Answer 2

Mycobacterium tuberculosis

Mycobacterium Bovis

Mycobacterium Africanum

M Avium - common in HIV

M Abscessus - common in children with CF

Question 3

What are the signs and symptoms of TB?

Answer 3

Night sweats

Weight loss - rabid

Cough

Fever

Fatigue

Extrapulmonary TB - LN, larynx, pleura, brain, kidneys, bones and joints

Question 4

How would you investigate TB?

Answer 4

X-ray = cavitation (not always in the apex), patchy consolidation, fibrosis

Interferon gamma

• does not diff between active and latent
• -ve result doesn’t mean the pt doesn’t have active TB

CT = coin lesion, patchy consolidation

Sputum x3 (C+S) = AFBs acid fast bacillus

Screen for HIV (BBV) = correlation

Bronchoscopy = rule out malignancy

Bronchoalveolar lavage (BAL) smear

PCR for TB DNA

Question 5

How would you manage TB?

Answer 5

RIPE - rifampicin (urine orange) (cytochrome P450 - interacts with methadone, hormonal contraceptives), isoniazid, pyrazinamide, ethambutol (all 4 for 2 months R+ I for a further 2 months) 
o	Sickness 
o	Feel like arthritis
o	Itchy
o	Liver toxicity 
o	Blindness
o	Peripheral neuropathy 

After 2 weeks of treatment you can go back to work

2nd line drugs = Quinolones

Contact tracing = family, work

IGRA = latent TB (does not diff between active and latent)

Question 6

What are the complications of TB?

Answer 6

Mortality

Lung resection

Question 7

What are the principles of TB contact tracing?

Answer 7

Identify those who require treatment

Control further spread

Identify genetic evolution of the TB strain

Question 8

If a patient with TB develops a headache and neck stiffness what might you be concerned about and how would you investigate this further?

Answer 8

Meningitis like symptoms lead me to believe the brain may now be infected with TB

Take a LP sample = C + S for TB
- CT head = ?lesion

Question 9

How is a diagnosis of Latent TB made and, if confirmed, what treatment should be offered?

Answer 9

Interferon Gamma Releasing Assays (IGRA) = Detection of antigen- specific IFN-gamma production

We do not treat latent TB, 95% will self cure, the further 5% will reactivate at which point we will treat with RIPE. We can also perform risk reduction for the factors that increase the risk of reactivation = alcohol, drug users, malignancy, kidney disease