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Microbio L10
| Question | Answer |
|---|---|
| Host-Microbe Interactions | Hosts are constantly interacting with microbes Transient populations vs commensals Populations in flux |
| Commensal populations: | Descent in digestive, skin, urogenital, and respiratory tracts - Compete with pathogens - Make nutrients - Promote immunity |
| Commensals should not | leak into any part of your body!!! Yeast on skin? Okay. In your skin? BAD |
| Dysbiosis | - Disruption of normal microbiota (particularly in gut) - Makes space for pathogens - Some microbiota can be opportunistic - Dislocation of normal microbiome can be dangerous too |
| hi | hi |
| Pathogenicity | ability of a microbe to cause disease |
| Virulence | severity of that disease |
| Virulence factor | mechanisms pathogens use to overcome host defenses Requires energy, so microbes only keep what is needed |
| 5 Categories of virulence factors | 1. To do things (toxins) 2. To evade (immune system evasion) 3. To stick to right tissue (adhesion) 4. To eat (nutrient acquisition) 5. To get in/through cells (invasion |
| Toxins | Generate adverse functions in the host, that are beneficial to the pathogen in some way |
| Toxins example | Make intestinal cells leaky, induce diarrhea, help spread cholera |
| Endotoxin | Piece of LPS (lipid A) released from dying Gram-bacteria Causes fever, chills, inflammation, nausea, low blood pressure |
| Endotoxin auses | Causes fever, chills, inflammation, nausea, low blood pressure |
| High levels in blood = | septic shock |
| How LPS endotoxin works in the body | Over activates immune system, so now you blood is not staying in blood vessels. Organs are deprived of oxygen and nutrients/ |
| Exotoxins | Secreted from live bacteria, highly diverse 3 types! |
| 3 types of exotoxins | 1. Cause improper signaling outside the cell 2. Cause improper signaling inside the cell 3. Get into the cells and just rip them apart |
| Host factors and virulence Some host factors can impact disease severity Example in covid 19.... | Example: covid-19 Asymptomatic in children More circulation in men |
| Transmission and Virulence | Must balance virulence with ability to transmit |
| If disease too severe | the patient won't move to interact with other potential hosts So balance high transmissibility with not-too-severe symptoms |
| Not true for | vehicle/vector-borne diseases They don't care if host is bedridden if water or a mosquito, will pick up pathogen and transport |
| R0 | Number of new cases created by a single case - In a complete susceptible population - Measure of infectivity |
| Virulence can also be influenced by | The environment Example: lab grown strains are attenuated (weakened) |
| Dosage of pathogen influences | disease |
| Id50 | how many cells/virion needed to establish infection in 50% of susceptible hosts Infectivity measure The lower the number, the less scary the thing is |
| LD50 | how many cells/virions needed to kill 50% of untreated hosts pathogenicity/virulence measure |
| Steps to infection | 1. Entry 2. Adherence 3. Invasion 4. Evasion |
| 1st Steps of infection Entry Portals of entry: | 1. Skin 2. Parenteral (bypass skin) 3. GI (common is fecal-oral) 4. Respiratory 5. Urogenital (common is STDs) |
| 2nd Steps of infection Adherence | Stick to proper tissues!!! Use adhesins - structures/proteins to stick (fimbrae, capsules, spike proteins) Biofilms - Use quorum sensing to switch between swimming and adhesion - Enhanced virulence |
| 3rd Steps of infection Invasion | Where will the pathogen live? To get nutrients Use invasions! Cellular damage leads to cytopathic effects Loss of cells/cell functions |
| 4th Steps of infection Evasions | Hide from immune system Masking (wearing the skin of our own cells), mimicry variation Undermine immune system Suppress immune signaling Avoid phagocytosis |
| 5th Steps of infection Exit transmission | Same portals as portals of entry Maintain the reservoir |
| Healthcare precautions: | Biosafety levels Minimize contact/chances for transmission Treat all material as if it is biohazardous |
Created by:
liladdoyle