Tuberculosis Flashcards
what bacteria causes tuberculosis?
Mycobacteria Tuberculosis complex (M. tuberculosis, M.bovis, M.africanumi)
Describe the progression of a TB infection
after inhalation of droplets containing M.TB
M. Tb enters macrophages and replicates
after a few weeks induces a T lymphocytic response (release of Interferon gamma)
- immediate clearance
- or primary disase = immediate onset of active disease
- latent infection
- reactivation of existing disease
describe the progression of primary tuberculosis disease
- droplets inhaled
- innate system fails to eliminate infection
- proliferation within alveolar macrophages
- in lungs, production of chemokines/cytokines which attract other phagocytic cells
- formation of tubercle (granulomatous structure)
- uncontrolled replication (enlarging tubercle)
- continued proliferation of bacilli until cell mediated immunity
- *variable course due to variability of immune respone*
finish the sentence
‘reactivated cases of TB tends to be….”
tends to be localized unless immunosupresed
these also tend to cause haemoptysis b/c more necrotising
what are the clinical features of TB ?
primary infection - flu-like illness, features of delayed hypersensitivity. fever, weight loss, night sweats
post primary = parenchyma/plura, lymphatic, pericardial, CNS, hepatic, miliary, skeletal, testicular
what drug was released in 1952 to treat TB?
streptomycin
what is the difference between primary infection and post-primary infection?
primary infection:majority resolve and never develop reactivation
post-primary infection = due to reactivation/reinfection
how do you identify TB?
manteaux test (only if they have had for more than 2 weeks)- Tb peptides introduced to subcutaneous layer - measure the ‘bubble’ 48 hours later
interferon gamma assay- blood culture with Tb and look for an interferon gamma production indicating T lymphocytic sensitivity to Tb
ziehl-neelson test of sputum
what sort of investigations should you do to diagnose Tb?
- FBC
- ESR
- CRP
- Renal
- LFTs
- CXR
what is the gold standard diagnosis of TB?
culture is the gold standard
biopsy of the granuloma
how do we diagnose latent TB?
positive tuberculin test (mantoux or heaf test) = problem with false positive due to BCG vaccination
or
positiver interferon gamma releasing assay (IGRA)= differentiates false from true positive TB skin tests, by testing antigens which are not present in the mantoux test
what is the first line treatment for tuberculosis?
”RIPE”
- Rifampicin
- Isoniazid
- Pyrazinamide
- Ethambutol
- four drugs for 2 months and maintenance (2 drugs for 4 months once sensitivity is identified
- Total of 6 months worth of therapy
when might you consider placing a TB patient on corticosteroids?
if they have pericarditis, meningitis, compression neuropathy, pleural effusion, w/ severe systemic disease
Why is TB the most common opportunistic infection in HIV?
- CD4+ depletion
- alveolar macrophages necrosis
- HIV replication increases in alveolar macrophages and peripheral lymphocytes when exposed to MTb antigens and cytokines
how do we treat latent disease?
if they have a positive tuberculin skin test but no active disease
treat with isoniazid (unless resistant)
