Relatively straightforward lecture just talks about TB which is great
Objectives
- Discuss the epidemiology of mycobacterium tuberculosis
- Understand the disease caused yb M tuberculosis
- Discuss the host pathogen interaction in tuber culosis
- Discuss how to diagnose active and latent m tuberculosis infection
Context
Tb is a historical killer Mortality has been reducing since 1900s TB is still really problematic in africa and asia
Tuberculosis
Mycobacterium tuberculosis
Acid fast bacillis Rich is call wall lipids, perticularly mycolic acid (which is hydrophobic). Slow growing. faculative intracellular pathoogen
Tuberculosis complex
7 bacteria which transmit tuberculosis
one is mycobacteria bovis
Transmission of TB
mainly spread through aerosols. It is good at this
Pathogenesis
Environmental exposure leads to infection which can lead to containment and persistance (latent infection) which can lead to reactivation
from infection 5-10% lead to primary tuberculosis from reactiation is also known as miliary TB (extra pulmonary TB)
Infection
Macrophage try to phagocytose the tuberculosis bacterium and then live and reproduce inside the cell
Granulomas
Granulomas form to contain the tuberculosis these force the Tb to be in stressed state which switches them to low power mode
however granlomas can become necrotic and rupture
An aside on CD4+ cells
Th1 cells produce IFNy and TNF alpha which activate macrophages TH17 calls produce IL-17 which activate neutrophils
CD8+ cells can kill infected macrophages
The IFNy can cause the macrophages to successfully consume tuberculosis
Laboratory diagnosis of tuberculosis
acid fast stain how you stain for TB
new method is a machine that just detects it in sputum samples the machina also tests for ampcillin resistance
Gold standard is culture in solid or automated liquic cultures
Susceptibility testing on cultures are really useful for figuring out what to use
Treatment of TB
multiple drugs to prevent resistance
treatment for at least 6-9 months dormant M tuberculosis necessitates prolonged treatment,
This is a highly protocolised disease
Barriers to therapy
long treatment duration complex regiment toxic effects in combination with antiretrovirals drug resistant TB and XDR TB
Treatment fo MDR/RR/preXDr and XDR tb is bedaquiline + pretomanid + linezolid+ moxifloxacin
Testing for latent TB infection
interferon famma release assay
tuberculin skin test inject TB protein and watch for reaction
Why test for thi? Identify individuals at increased risk for developing active TB