tuberculosis Flashcards
where are majority of cases
Africa and Asia
what does it co-infect with
HIV
what are the 4 main species
- mycobacterium tuberculosis
- mycobacterium bovis
- mycobacterium africanum
- mycobacterium microti
does it stain well
no
what are they termed
acid fast bacilli
how does TB spread
via respiratory droplets
what happens once TB is inhaled into lungs
- alveolar macrophages ingest bacteria
- the bacilli then proliferate inside the macrophage and cause release of neutrophil chemoattractants and cytokines
- results in inflammatory cell infiltrate reaching lung and draining hilar lymph nodes
what does macrophage present the antigen to
T lymphocytes
what type of hypersensitivity
delayed
what does the delayed hypersensitivity result in
tissue necrosis and formation of a granuloma
what does granulomatous lesions consist of
central area of necrotic material = caseation
what happens to caseated area if they heal
become calcified
can it lie dormant
yes
what is the focus termed
Ghon focus
what does Ghon focus look like on CXR
small, calcified nodule in upper parts
what are majority of TB cases primary or reactivated
reactivated
what can cause TB to reactivate
HIV
what are factors that implicate reactivation of TB
- HIV
- chemotherapy
- diabetes
- chronic kidney disease
- malnutrition
- ageing
different sites of TB
- pulmonary
- miliary
- central venous
- lymph nodes
what should be done for suspected TB
obtain tissue or fluid microscopy
what should be done for pulmonary TB
serial sputum samples on 3 occasion
symptoms of pulmonary TB
- productive cough
- haemoptysis
- weight loss
- fevers
- sweats (end of day and night)
- hoarse voice
- severe cough
- pleuritic pain
what is seen on pulmonary TB CXR
- consolidation with or without cavitation
- pleural effusion
- thickening of mediastinum caused by hilar adenopathy
what is most common site for TB
pulmonary
what is second most common site
lymph node
what does lymph node present with
firm, non-tender enlargement
what can be seen on CT of lymph node TB
central area appears necrotic
how does miliary TB occur through
haemotgenous spread of the bacilli
what does CXR look like in miliary TB
multiple nodules that look like millet seeds
what stain is used
Ziehl-Neelsen
what is done to check for rifampicin resistance
PCR
how long is treatment
6 months
what drugs are used
- rifampicin
- isoniazid
- pyrazinamide
- ethambutol
side effects of rifampicin
- induces liver enzymes
- stains body secretions pink (urine, tears, sweat)
- makes oral contraception non effective
side effects of isoniazid
- polyneuropathy
- B6 deficiency
- allergic reactions (skin rash, fever)
side effect of pyrazinamide
- hepatic toxicity
- reduces renal excretion
side effect of ethambutol.
- colour blindness (for green)
why does drug resistance occur
miss-use and not taking drugs for long enough
why does mycobacterium bovis occur
due to consumption of unpasteurised milk
how is m.bovis diagnosed
acid-fast staining
- culture of tissues and sputum
treatment of m.bovis
- isoniazid
- rifampicin
- ethambutol
- pyranzinamide resistance is common
what can it be co-infected with
HIV
what is the vaccine
BCG vaccine
what type of hypersensitivity
type IV hypersensitivity
what type of focus
Ghon focus
what type of necrosis
caseous
where is secondary TB usually
in lung apices
