Flashcards
Dr Taylor Smith. Lec 1. Cryptococus
Cards in this deck (18)
- 1What fungus is in question in this lectureThe fungus cryptococcus neoformans
- 2What is cryptococcus neoformans?An opportunistic pathogen. Blastomycete encapsulated yeast. Found in soil, some tree species and pigeon droppings. Most infectious cases in HIV+ in sub saharan africa. Infects via lung and disseminates in CNS to cause cryptococcal meningitus
- 3Does cyrptococcus affect healthy individuals?No, their immune system can cope with the infection. It causes infection in immunocompromised people
- 4The first step of cryptococcus virulence is getting to the brain. How does it achieve this?It has to survive in the lung, grow at 37 degrees, be resistant to antimicrobial peptides, resist phagosytosis and resist immune cells
- 5The cryptococcus slime capsule:Capsule of slime around fungus. Made of a polysaccharide layer that contains GXM and GXMGal as well as mannoproteins. It protects everything beneath it like the cell membrane and the cell wall.
- 6What does the slime capsule help do?Reduce phagocytosis as it allows fungal cells to swell in size during infection. It becomes swole at 37 degrees. It is also responsible for allowing it to grow at 37 degrees, resist killing by peptides and phagocytosis and resist the immune cells
- 7What it malanin?A black/brown pigment. Has negative charge and is hydrophobic. Formed by oxidative polymerisation of the pheolic compound LACCASE.
- 8Relationship between cryptococcus and melanin?Crypto increases melanin during infection. It provides resistance to acids and proteases and oxidative stress. Reduces T cell responses. Helps crypto grow at 37 degrees.
- 9How does crypto avoid phagocytosis?It is faculatative intracellular pathogen that can not only survive in macrophages but replicate there too.
- 10What is vomocytosis?Crypto cells can jump out of a macrophage. Or, it could be the macrophage spitting the crypto out as it is unable to digest it
- 11The next step in crypto infection is travelling the blood brain barrierThere is a Trojan horse theory here: cyrptococcus hides inside of macrophages to disguise it and protect it from the immune system as it sneaks into the CNS
- 12Next, it needs to cross the blood brain barrier. There are three theories about this:Transcytosis theory, trojan horse theory, paracellular theory
- 13Transcytosis theory:Crypto exits macrophage and is endo/exocytosed through endothelial cells of the blood brain barrier
- 14Trojan horse theory:Crypto stays in the macrophage and the entire macrophage squeezes through the endothelial cells of the blood brain barrier tight junctions
- 15Paracellular theory:Crypto exists macrophage and and moves through the tight junctions between endothelial cells, perhaps using unknown mechanisms to loosen the tight junctions
- 16Evolution of crytococcus virulence factors?Some theories say that crypto evolved regardless of its infection in humans and that crypto just happens to be able to survive in humans. Amoebas used to engulf cyrpto so did learning to survive inside amoebas equal survival in humans too?
- 17Summary of what slime capsule is good forPrevent desiccation and prevents phagocytosis
- 18Summary of function of melanin in crypto?Provides UV shield, extreme hot/cold resistance, etc
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- Microbes and Man Flashcards on Dr Taylor Smith. Lec 1. Cryptococus, created by Emma Lloyd on 06/05/2019.
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