Term
| Why does Mtb stain acid fast in the Zeil-Neilsen staining procedure? |
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Definition
| The mycolic acid layer - despite it is actually gram +tive |
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Term
| How much of the worlds population may harbour TB? |
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Definition
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Term
| What is used as a model for Mtb is labs and why? |
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Definition
| M. smegmatis, MTB only grows in humans |
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Term
| What does the vaccination against TB use? |
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Definition
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Term
| What is the method by which Mtb causes disease? |
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Definition
Bacteria inhaled, and enter macrophages in lung alveolae
Invade lung tissue and for tubercules (which can later spread to other parts of the body)
The tubercules are aggregates of activated macrophages which enclose live Mtb replicating.
The tubercles block airways, destroying lung function, whilst the Mtb survives |
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Term
| How can Mtb cells be more easily found in infected tissue? |
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Definition
| They can be labelled by molecular beacons - fluorescent probes which are activated by an Mtb enzyme |
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Term
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Definition
| Aggregates of infected macrophages - Mtb replicates inside, killing the cells |
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Term
| What stages does the granuloma go through? |
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Definition
| Solid, necrotic, (centre cells have died, Caseous - most cells have died, Mtb is starting to leak out |
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Term
| Why is it difficult to deliver drugs inside granulomas? |
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Definition
| Thick mycolic acid layers and minimal metabolism so no active transport |
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Term
| How is it thought Mtb can be reactivated using scouts? |
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Definition
| Scouts use resuscitation promoting factors to stimulate dormant Mtb - Mtb has 5 preducted rpf genes |
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Term
| What is the host response to Mtb? |
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Definition
Acidification of the phagosome
Production of ROS and RNS
Production of hydrolytic enzymes
Cationic Anti-microbial Peptides (CAMPs) - result in permeabilisation of the cell membrane |
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Term
| How does Mtb defend against host ROS and RNS stress? |
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Definition
KatG - catalase peroxidase enzyme - degrades hydrogen perozide, the most common ROS, to produce water and oxygen
SodA and SodC - superoxide dismutase enzymes degrade superoxides
Mycothiol - reduced sulfur containing compound which helps keep the cytoplasm reduced when the pH is low and there is oxidative stress
NADH dependent peroxidase and peroxinitrite reductase degrade ROS or RNS
Truncated haemoglobins detoxify reactive nitrogen or oxygen species |
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Term
| How does Mtb survive acidification of the phagosome? |
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Definition
| mycoloic acid, OmpATb proteins in the outermembrane, slows the macrophages maturation and acidication process |
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Term
| What is HbN, where is it located, how is it modified what does it do? |
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Definition
| A truncated haemoglobin, On the cell surface, post-translationally glycosylated, protects against NO species and modulates immune response by suppressing expression of CD80 and CD86 - interefering with T cell activation |
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Term
| How does Mtb get the raw materials for mycolic acid synthesis? |
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Definition
| degrade host cell membrane lipids and do de novo synthesis |
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Term
| Why are ESAT-6 CFP10 proteins important in Mtb? |
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Definition
| When they are deleted Mtb cannot spread from macrophage to macrophage or through lun tissue |
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Term
| What encodes the type VII secretion system? |
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Definition
| the H37Rv region - this also encodes PE-PPE proteins |
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Term
| What do PE PPE proteins do? |
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Definition
| Can recognise and bind to each other for specific functions - can be diversified for many roles |
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