TB Flashcards
Classification of myobacteria
- TB
- Non-tuberculous myobacteria (rapid growing, non-rapid growing or other)
Process of TB disease manifestation
- Aerolised TB particle inhaled
- Particle impacts in distal airway. TB cell wall constitents iniatae phagocytosis, complement receptors, mannose receptors. TB is engulfed (phagocytosed) by pulmonary phagocytes.
*TB wants to be phagocytosed - TB resists lysis by lyosome
- TB has many adaptions that resist killing
- resistant to killing (tough cell wall, free radical scavengars, superoxide dismutase
- Decrease in apoptosis
-Block IFN y signalling
-blocks antigen presentation to T cells
- Vesicles altered
- blocked proton pump, failed maturation, altered fusion with phagosome
lecture Slide for diagram
Label histology slide for TB
Lecture Slide
What are all the options post TB primary infection (diagram)
Lecture Slide
Outcomes of TB infection
- primary focus (Ghons focus) - lung and node
- Pleural
- Cavitation
- Symptoms from increase in nodes
- TB bronchopneumonia
- pericardial disease
- Miliary TB
How do you catch TB
Droplet/airborne
Risks for catching TB
Recipient:
Household contact
children
immune suppression
institutional care (prisoners)
healthcare workers
Transmission:
Pulmonary disease
delayed diagnosis
failure to cover mouth when coughing
How to diagnose TB
- Suspicion
- Chest X ray
- Sputum specimens
- TB PCR
- TB culture
How to perform Ziehl-Neelsen stain
and results
- Smear specimen on slide
- apply carbol-fuchsin stain
- Apply heat
- Wash with HCl in ethanol
Mycobaterua retain the stain (incoperated into the lipid cell wall) and most other bacteria lose the stain
How to diagnose latent TB
TB protein given intradermally and after 3 days if there is an inflammatory lump present then the person is hypersensitive to TB antigen
Interferon gamma release assay (quantiferon gold)
- whole blood into test tube
- Add mitogen to make lymphocytes proliferate - they release interferon gamma (+ control)
- Add TB antigens - sensitised lymphocytes will proliferate and release interferon gamma (this person has been exposed to TB in the past)
TB managment
- Get the patient better
- Prevent transmission
TB treatment
- why not use typical antibiotics
Eg pencillin which binds to the transpeptidase enzymes in the cell wall causing it to lose structural intergrity leading to the bacteria dying doesnt work in TB because TB doesnt rely on transpeptidase in its cell wall SO have to use…
- Rifampicin (RNA target)
- Isoniazid (cell wall -mycolic acid target)
- pyrazinamide (sterilise rapidly dividing bacteria)
- Ethambutol (protect against drug resistance)
