Tuberculosis Flashcards
Organism responsible for TB
mycobacteria
Various species of TB responsible for human disease
Myobacterium tuberculosis
M Bovis (bovine TB)
Mycobacteria
non-motile bacillus
very slowly growing
aerobic
Transmission of mycobacterium tuberculosis
source
case of ‘open’ pulmonary TB, coughing, sneezing
respiratory droplets evaporate
remain airborne for long period of time
Inhaled TB
larger droplet nuclei impact on airways
smaller droplets impact on alveoli and slowly proliferate
Mycobacterium bovis
consumption of infected cows milk deposited in cervical, intestinal lymph nodes
Immunopathology of TB
accumulation of macrophages, epithelial and longhand cells –> GRANULOMA
TB elicits a …… cell mediated immunological response
Th1
Th1 cell mediated response is a TWO EDGED SWORD
- eliminates/ reduces number of invading mycobacteria
2. tissue destruction is a consequence of activation of macrophages
Susceptible host to TB
elderly
malnutrition
TB primary infection
no preceding exposure or immunity
usually children (80% infected alveolus)
mycobacteria spreads via the lymphatics to drain lymph nodes
haematogenous seeding of mycobacteria to all organs of the body (lungs, bone etc)
TB symptoms
usually no symptoms
fever, malaise
Primary infection progression
primary focus continues to enlarge
lobar collapse due to enlarged lymph that compress bronchi
poor prognosis
6-12 months after TB
X-ray shows widespread small granulomata
Tuberculous pleural effusion
Post primary disease (TB)
- reactivation of mycobacterium from latent primary infection disseminated by the blood stream around the body
- New re-infection from outside source, susceptible previously infected host
(different host response because of previous sensitisation)
Post primary diseases
Pulmonary disease
lymph nodes
bones and joints
genito-urinary
male infertility
Post-primary pulmonary tuberculosis clinically
may occur at any age - usually the reactivation of latent disease
May not be any symptoms for months
Progressive (several months)
Respiratory: Cough, sputum, haemoptysis, pleuritic chest pain, SOB
‘index of suspicion’ for TB
immunosuppressed
malnutrition
Diabetes
adolescence, elderly
TB essential investigations
3 sputum specimens on successive days
(sputum smear/ sputum culture)
CXR
Further investigations if sputum is negative
CT scan of thorax
bronchoscopy (bronchial histology/ biopsy)
Pleural aspiration and biopsy if pleural effusion
Treatment of TB (surgical) and old school lol
Collapse down the cavity, anaerobic condition, phrenic crush, artificial pneumothorax, pneumoperitoneum, thoracoplasty, lung resection
Modern treatment of TB
multiple drug treatment
therapy for 6 months
Current TB regimes
2 months - 4 drugs
4 months - 2 drugs
rifampicin and
isoniazid
Likelihood of infection with TB depends on
duration of contact
intensity of infection
Screening TB
tuberculin test
