lecture 3- controlling microorganisms Flashcards
(32 cards)
disinfection
destroys most microbial life, reducing contamination on inanimate surfaces
- destroy vegetative (growing) cells
- doesn’t kill bacterial spores
- conditions too harsh to use on people
antisepsis
destroys most microbial life, reducing contamination on a living surface
-Use “antiseptics”, chemical agents that kill microbes
sterilization
destruction of all microbial life
-used for inanimate objects, never living tissue as too harsh
what are cells?
packages of water, genetics, proteins, sometimes have cell wall
highest resistance
- bacterial endospores
- pirons (infectious proteins)
- no moving parts, low enzymes therefore few targets to kill
moderate resistance
- Protozoan cysts (kind of like a spore)
- fungal sexual spores,
- naked viruses (does not have a membrane)
- resistant bacteria (like some Gram+)
least resistance
- growing bacterial cells (expire quickly without water)
- growing eukaryotic cells
- enveloped viruses (c/membrane - HIV)
- yeast
how are viruses resistant?
- dont need food
- many don’t need water
how are bacterial spores resistant?
- some Gram-positive make spores
- don’t need food
- strong protein coat protects genetic material and enzymes inside
- low water content
how are some bacteria resistant?
ESP. Gram +
- thick cell wall
- resist desiccation (drying)
how are eukaryotes resistant?
- protozoan cysts
- fungal spores
- Strong protein coats
- Don’t need water
how is microbial death characterized?
- cell structures dysfunctional (irreversible damage)
- cant reproduce
- Need microbicidal agent
-cidal
killed
-static
not killed, won’t grow in mass numbers, removes them
what affects microbial killing rate
- number of organisms (harder to kill lots - fewer cells, less sterilization time)
- type of microbial population
- concentration of decontaminating agents (less concentrated, less killing)
- mode of action for agent
- presence of solvents, organic matter, and inhibitors
- environment temp and pH
how do you kill microbes?
target weaknesses
-denaturation of:
cell wall
cell membrane
enzymes
genetic material
MOA: targeting cell membrane
-when cell membrane is disrupted, selective permeability is lost - cytoplasm leaks out causing cell death
MOA: inhibiting enzyme functioning
- proteins have a specific shape (native shape) when this is disrupted the protein becomes denatured
- enzyme active sites can’t accept substrate to function
explain the difference between moist heat and dry heat and how they kill microbes
moist heat is for coagulation and denaturation
dry heat removes water from organisms (incineration)
*moist heat is more destructive b/c water has ability to kill proteins within organism (takes less time sterilize)
how does the autoclave work?
high pressure concentration of steam creating a destructive moist heat
what is pasteurization used for? how is it accomplished?
- disinfect beverages
- heat is applied to liquid to kill pathogens, but doesn’t denature proteins (flavour and texture in tact)
- doesnt kill endospores, and it is NOT STERILE
what are the two methods of pasteurization?
flash: expose to 71.6°C for 15 seconds
Batch: expose to 63°C to 66°C for 30 minutes
MOA: Ionizing radiation
ionizing: energy from-rays, gamma-rays and high energy UV light to liberate e- from atoms
* can penetrate and get hidden microbes, can inhibit proteins
what is ionizing radiation used to sterilize?
food products, medical products
