Chapter 26 Flashcards
What is sterilization
The killing or removal of ALL viable organisms
What is inhibition
Effectively limiting/inhibiting microbial growth. Ex. dehydration, refrigeration, freezing, etc
What is decontamination
Treatment of objects, surfaces, etc to make them clean and safe to handle
What is disinfection
Removal of all active pathogens, but not necessarily all microorganisms and not spores (dormant and not active)
What is widely used for killing microbes and why
Heat - high temperatures denatures macromolecules and DNA, which kills microbes
What is the decimal reduction time
The amount of time required to reduce viability tenfold, is determine in relation to the temperature and growth conditions
What can survive heat
Endospores and other types of spores can survive heat treatment that would normally kill vegetative cells
What is an autoclave
A device that uses steam under presure to produce 121C at 15 PSI, allows the termpature of water to get above 100C without evaporating
What are autoclaves used for
Used to sterilize both liquids and dry items
How long does it take to sterilize small volumes
About 15 minutes, it takes larger volumes more time because it takes longer to heat up large amounts
What is pasteurization
Precisely controlled heat and time to reduce the microbial load in heat-sensitive liquids, such as milk. It kills all pathogens in the product but does NOT kill all the normal microorganisms. It avoids the altering of product quality
What is used in radiation sterilization
Microwaves, UV, X-rays, gamma rays, and electrons can kill microbes. Exposing microbes to high enough energy can damage them to death
What is UV useful for
UV is useful for decontamination of surfaces because it can’t penetrate solid, opaque, or light-absorbing material
What is ionizing radiation
High energy electromagnetic radiation that produce ions and other reactive molecules that damage cell components, some microorganisms can be more resistant to this than others
What is filter filtration
Filtration avoids the use of heat on sensitive liquids and gases. The pores of filter are too small for organisms to pass through
What are depth filters
HEPA filters
What are membrane filters
Function more like a seive
What are the 3 possible antimicrobial agents
Bacteriostatic, bacteriocidal, and bacteriolytic
What is bacteriostatic
After adding the agent, the number of cells and number of viable cells have stopped increasing and is leveling off. They are still alive just not growing anymore
What is bacteriocidal
The cells are killed after the agent is added and the number of viable cells decrease while the number of cells stops increasing
What is bacteriolytic
An agent that will cause the cells to break apart (penicillin) as the cells grow. The cells will burst leading to the decline of the number of cells as well as the number of viable cells
What is minimum inhibitory concentration
MIC - is the smallest amount of an agent needed to inhibit growth of a microorganisms. It varies with the organism and its numbers as well as the abiotic factors such as temp, pH, and medium
Describe a disc diffusion assay
A antimicrobial agent is added to filter paper disc, which is then placed on a petri plate inoculated with a lawn of the test bacteria. The MIC is reached at some distance from the disc
What is the zone of inhibition
The area of no growth of the test bacteria around the disc, this zone can be measured and compared. Larger zone of inhibition means its more effective
