Mycobacterium & Tuberculosis (TB) Flashcards
Vitamin D link to Tb
Vit D activates macrophages to destroy mycobacteria
Deficienct in ethnic UK pops
What is tested if suspected Tb
HIV and Vit D
Tx of Tb
Isoniazid, rifampicin, pyrazinamide and ethambutol for 2m
Isoniazid + rifampicin for 4m
Min length of Tx, why?
6m to stop resistant strains
Why may pt want to stop taking meds after 3 weeks?
Non-infectious after 2 weeks
Feel better after 2-4w
BCG vaccine
Child Tb only
No impact of HIV related Tb
Prevents infection only, not disease
Invalidates tuberculin skin test
HIV and TB
HIV increase risk of acquiring TB by destroying IS
TB makes HIV worse by increasing replication rate
Mycobacterium tuberculosis
Obligate aerobes - upper lobes of lungs.
Facultative intracellular parasite - lipid wall allows it to live in macrophages as it doesn’t activate macro.
Slow generation
TB spread
aerosol coughs sneezes
close contact w infected
small so not pulled down by gravity
At risk groups
HIV infected Elderly Immunosuppressed e.g. chemo, transplants, steroids Live in crowded unhealthy places High rate country TB youth exposure Prisoners, drug addicts, alcoholic Malnourished
Path of TB to alveoli
Droplet nuclei inhaled
Macrophages take up in alveoli but not activated
Nuclei reach alveoli and infect (usually at base of lung)
Gohn focus
Granuloma in lung formed by body IS reacting to infection
primary complex
GF + enlarged LN
Secondary TB causes
Dormant mycobacteria reactivated
Reinfection of previously infected
Secondary TB xray sign
Shadow upper lung on chest xray
Ghon complex
Healed area of primary lesion
Secondary TB pathway
Caseous centres liquefy
Organism grows rapidly
Large Ag load
Bronchi walls necrotise and rupture leading to a cavity
Allow lots of O2 to organism which it likes as is an aerobe
Organism spills out of rupture into airway and spreads to other areas of lung
Miliary TB
IS overwhelmed and organism spreads into blood and therefore to body.
Miliary seeds on xray
Infection vs disease
Both have org present and + tuberculin skin test.
Differences:
Infection = Chest X-ray normal Sputum smears negative Sputum culture negative No symptoms Not infectious Not defined as a case of TB
Diseases= Lesion on chest X-ray Sputum smear positive Sputum culture positive Symptoms Infectious Defined as a case of TB
What are TB symptoms due to?
Cytokines
TB symptoms
Cough (+/- sputum) WL Swollen glands Fever Night sweats Tired + unwell Cough up blood (Haemoptysis)
Stop MDR-TB
standardized drug regimens
directly observed treatment (DOT)
good supply of high quality drugs
isolation of infectious patients
Culture media
Ziehl-Neelsen stain - stains red if +
need a large load to get +
