Tuberculosis (DISEASE MECHANISMS) Flashcards
Upon exposure with T the pathogens are engulfed within ____ where they replicate
macrophages
TB pathogens are kept in ‘prisons’ called
granulomas
After infection _% remain well
50% __ _ ______
_% have lifetime risk of disease of which _% _______ and _% _____________
90% clear TB spontaneously 10 5% primary TB 5% reactivation of latent disease
The symptoms of TB are _______ and have a _____ onset
subacute
gradual
What are the general symptoms of TB?
Malaise
Weight loss
Night sweats
What are the respiratory symptoms of TB?
Cough
Haemoptysis
Breathlessness
Upper zone crackles on asucultation
What are the meningeal symptoms of TB?
Headaches
Drowsy
Fits
What are the GI symptoms of TB
Pain
Bower obstruction
Perforation
Peritonitis
What are the symptoms of spinal TB?
Pain
Deformity
Paraplegia
What is paraplegia?
Impairment in motor or sensory function of the lower extremities
How can TB in the lymph nodes be detected?
Lymphodenopathy
TB can present as a cold abscess - what is a cold abscess?
Collection of pus without pain or acute inflammation
What are the pericardial symptoms of TB?
Tamponade
What are the real symptoms of TB?
Renal failure
How can TB in the joints present?
Septic arthritis - cold mono arthritis or large joints
How can TB in the adrenal present?
Hypoadrenalism
How can TB be diagnosed using histology?
Multinucleate giant cell granulomas
Caseous necrosis
Sometimes visible mycobacteria
What would be noticeable on a CXR of a patient with TB?
Upper lobe predominance Cavity formation Tissue destruction Scarring and shrinkage Heals with calcification
How is TB treated?
2 months of Rifampicin, Isoniazid, Pyrozinamide and Ethambutol
4 months of Rifampicin and Isoniazid
What are the side effect of Rifampicin?
Colours urine and all bodily fluids orange
Potent inducer of cytochrome enzymes causing rapid breakdown of all steroid molecules (inc. hormonal contraception) and opiate analgesics and many other drugs
What are the side effects of ethambutol?
Can cause optic neuritis
What are the different types of drug resistance?
Single resistance
Multi-drug resistance
Extensive resistance
Which TB drug shows single resistance?
Isoniazid
Which TB drugs show MDR?
Rifampicin
Isoniazid
Which TB drugs show extensive drug resistance?
MDR
Quinolone
Injectables
A patient with latent TB infection would present …
asymptomatic
negative culture
What is the criteria for latent TB?
No evidence of active TB
Evidence of previous TB infection (history before 1960 / calcification on CXR / Exposure to high prevalence areas)
What are the two tests to determine if someone has had previous TB exposure?
Interferon Gamma Release Assay blood test
Mantoux tuberculin skin test
How does the Interferon gamma release assay test work?
Assays look for interferon gamma specific to antigens found only in M. tuberculosis
What are the advantages of the interferon gamma release assay test?
High specificity
Only requires 1 visit
Doesn’t react with BCG
How does the mantoux tuberculin skin test work?
Tuberculin is a protein derived from mycobacteria culture - detects any previous TB exposure
What are the disadvantages of the mantoux tuberculin skin test compared to interferon gamma release assay?
Requires 2 visits
Lots of false positives and negatives
Cannot distinguish BCG
How can latent TB be treated?
6 months of isoniazid or 3 months of rifampicin + isoniazid
Which drug must NOT be given to a patient with latent TB?
Anti-TNF
Is it an option to simply not treat latent TB?
Yes
How can TB be prevented?
Contact tracing Isolation of infected Screening (of high risk individuals) BCG immunisation Social measures (housing / nutrition)
How does the BCG immunisation work?
Attenuated strain of M. bovid
Intradermal injection
Where is BCG immunisation most effective?
Neonates of high risk families
TB is closely associated with which disease?
HIV
Which types of drugs can reactivate latent TB?
Steroids and other immunosuppressants
What are the main aspects of pleural infection?
Increasing incidence
Significant mortality
Doesn’t always follow pneumonia
Can rapidly coagulate and organise to form fibrosis peels even w/o antibiotics
What are the risk factor for pleural infection?
Diabetes mellitus Immunosuppression Gastro-oesophageal reflux Alcohol misses I.V. drug abuse
What is are the 3 types of pleural infection?
- Simple parapneumonic effusion
- Complicated parapneumonic effusion
Effusion - Empyema
What distinguishes a simple parapneumonic effusion?
Typically respond well to antibiotics
What distinguishes a complicated parapneumonic effusion?
Includes pus Gram-stain postive pH < 7.2 low glucose separations loculations
What distinguishes empyema?
Pus in pleural cavity
Typically, pleural effusions below _ cm don’t need to be drained?
1 cm
How are pleural effusions managed?
Antibiotics (often several weeks) Drain as needed Early discuss with surgeons if persistent sepsis Nutrition VTE prophylaxis Question role of fibrinolytic or Dnase Reassess if don't improve
