023 Case study TB Flashcards
What color does Mycobacteria stain in Ziehl - Neelsen?
Red
Describe the cell wall structure of M.tuberculosis
On top of the peptidoglycan layer, there is a arabinogalactan layer. This is covalently bonded to the mycolic acid on top. On the mycolic layer there is a layer of lipoarabinomannan.
What does acid-fast bacillus mean?
That once stained, it cannot be removed by acids.
What is the standard diagnosis method now?
Using PCR methods
What is the role of the mycolic acid layer?
It prevents attack by antibodies, enzymes, and oxygen radicals. It is very resistant to dehydration and dessication. It is impervious to many substances, and contains porins to facilitate hydrophilic substance transport.
Which Mycobacterium agent causes leprosy?
Mycobacterium leprae
In 1993, how much of the worlds population was estimated to be infected with M.tuberculosis?
2 billion people (1/3 of the population)
Why does M.tuberculosis have a characteristic slow growth rate? How long does it normally take to form colonies?
Because its cell wall is so thick and impermeable, it takes a long time for substances to move in and out for metabolism.
What is the function of Lipoarabinomannan?
Lipoarabinomannan will detect macrophages, inactivate them, and detect oxidative radicals.
What is the Mycobacterium agent that can be spread through unpasteurised milk?
Mycobacterium bovis
How many people die per year from the disease?
How many people develop active disease per year?
2 million people die from the disease
8-10 million people have active disease annually
Describe the host response against M.tuberculosis?
It is taken up by macrophages but they inhibit the phagolysosome fusion and also cause acidification of phagocytes. They can live in the macrophages, multiply intracellularly, and can be released when the cells die by aptosis. When TB is detected, it elicits a Th1 response, which releases pro-inflammatory cytokines (IFN gamma and IL12, TNF). This results in recruitment of immune cells. Cytotoxic T-cells also release granulysin. Granulomas are formed during chronic inflammation.
What can be used as an indication of chronic inflammation?
Granulomas, which are groups of macrophages called epitheloid cells that surround the M.tuberculosis, preventing spread.
Why dont antibody-mediated responses work in M.tuberculosis infections?
Because it is intracellular organism
What symptoms may occur? What would you see in chest X-ray?
You would see lung damage and granuloma appearance.
