24 - Mycobacterium Species Flashcards
1
Q
Mycobacterium
A
- “Fungus bacterium”, named due to mould-like pellicle that floats on liquid (hydrophobic)
- Rod shaped, non motile bacterial cells
- Slow growing, strict aerobes
2
Q
Characteristics of Mycobacterium
A
- Not classically gram positive or negative
- Unique, lipid rich cell wall (resists typical stains, thin layer of peptidoglycan, contains mycolic acids)
- Acid fast
3
Q
How are pathogenic species grouped
A
- Growth rate (rapid vs slow)
- Disease (TB or not RB)
- Or by both
4
Q
M. tuberculosis complex (MTBC)
A
- Slow growth rate
- Cord test positive
- All species capable of causing TB
- e.g. M. tuberculosis, africanum, bovis
5
Q
Non TB Mycobacteria (NTM)
A
- All species that doesn’t cause TB or leprosy
- Slow or rapid growth rate
- Cord test negative
6
Q
Tuberculous mycobacterial disease
A
- Mainly lung infection
- Weakness, weight loss, fever, cough
- Manifests slowly
- Airborne transmission
- Risk of transmission determined by
7
Q
TB/HIV co infection
A
- TB progresses more rapidly with untreated HIV (Greater risk of reactivation, faster disease progression)
- Delayed diagnosis
- Further immune dysfunction
7
Q
What is risk of transmission of TB determined by
A
- Infectious status of patient
- Proximity and frequency of contact
- Environmental factors
- Possible host factors in the exposed person
8
Q
Initial infection of TB
A
- Droplet nuclei inhaled (can contain 1-3 bacilli, and remain airborne for minutes to hours)
- After inhalation, droplet nuclei can reach the alveolar membrane
9
Q
Innate immune phase of TB
A
- Most Bacilli are contained or destroyed
- Some survive phagocytosis by blocking lysosome fusion with phagosome (replicate in macrophages, released when macrophages die)
- Major cell types: macrophages, neutrophils, dendritic & natural killer cells
- Bacilli grow until threshold number of organisms is reached
- No immediate host response as no toxin produced
10
Q
Adaptive immune phase in TB
A
- Bacteria released from macrophages travel to lymph nodes and present to lymphocytes
- Stimulates cell mediated immunity
11
Q
Cell mediated immune response in TB
A
- Recruitment and activation of T lymphocytes
- Release of lymphokines, monokines and cytokines by T cells
12
Q
Release of lymphokines, monokines and cytokines by T cells
A
- Promotes recruitment of cells to infection site
- Activates macrophages to kill bacilli
- Triggers formation of early granuloma - Macrophages fuse to form multi nucleated giant cells or differentiate into foamy cells and surround the granuloma
13
Q
latent TB
A
- Most bacilli die and granulomas heal
- Becomes latent TB (non-infectious)
14
Q
First effective drug in TB
A
Streptomycin
