Mycobacteria Flashcards
What species causes Tuberculosis
M. tuberculosis
What species causes Chronic lung infection
MAC
M. Kansasii
What species causes fish tank granuloma
M. Marinum
What species causes Buruli ulcer
M. ulcerans
What species causes leprosy
M. leprae
Are mycobacteria aerobic or anaerobic
Aerobic
Can mycobacteria be destained by acid and alcohol
No
Shape of mycobacteria
bacillus
Define bacillus
Rod-shaped, Gram-positive and aerobic
Where are mycobacteria found
Inside macrophages
Relative growth rate of mycobacteria
Slow REPRODUCTION
Slow GROWTH in Human
Slow GROWTH IN CULTURE
Slow RESPONSE TO TREATMENT
4 aspects of Koch’s postulates
- Bacteria should be found in all people with disease
- Bacteria should be isolated from the infected lesions in people with the disease
- Pure culture inoculated in a person should show symptoms of the disease
- Same bacteria should be isolated from the intentionally infected individual
Why are mycobacteria resistant to gram-stain
High lipid content with mycelia acids in the cell wall causing them to become v-shaped
What stain is needed for acid fast bacilli
Ziehl-Neelsen stain (AFB)
What are the three elements of the Ziehl-Neelsen stain
- Carbol fuchsin
- Acid Alcohol
- Methylene Blue
How much AFB is needed per ml sputum
10,000 AFB
Difference between Fluorochrome stains and AFB stain
Fluorochrome stains aid screening at lower power objective lenses
What colour does the Ziehl-Neelsen stain give when the test is positive for acid-fast bacilli
Red/Pink
How do we analyse nucleic acid of mycobacterium
PCR
Produces rapid results
What bacteria is PCR used for diagnosis and why
TB
Fast and specific
How do mycobacteria cause disease
- Acid fast bacilli are phagocytose and placed in phagolysosome
- Bacteria adapts to intracellular environment and withstands phagolysosomal killing
- Escapes to cytosol
- Host tries to kill mycobacterium via microbicidal molecules
- These assist in digestion and degradation by bacterial proteases
- Degraded into antigens for T cell presentations
Ignored by immune system
Describe the normal immunological process that take place following invasion of a pathogen
- CD4 cells produce INF-gamma
2. IL-12 further stimulates the release of INF gamma
What are granulomas
Lesions that arise in response to containing mycobacteria
How does mycobacteria granulomas form
- Macrophages become epithelioid cells
- Macrophages fuse together to form giant multinucleate cells
- T cells infiltrate the granuloma
- Central tissues necrose to form caveating granuloma
- Granuloma prevents nutrients from entering - starving the mycobacteria forming cavities