Disinfection & Sterilization Flashcards
Compare and contrast sterilization with sanitization
Both are cleaning methods but sterilization involves the destruction of all living microbes, spores, and viruses, sanitation only reduces the number of pathogens/discourages growth
What are the physical methods of disinfection
heat
radiation
filtration
How does heat attack cells?
destroys proteins and nucleic acids
water is removed
the minimum temp at which all bacteria in a culture will die within 10 minutes
Thermal Death Point (TDP)
DRT-value (decimal reduction time) defines what?
defines heat resistant bacteria
requires LONG periods of exposure
Dry heat
faster and effective at low temperatures
Moist heat
how does moist heat disrupt cells?
denatures proteins and coagulates them
application of steam heat and pressure, kills vegetative cells, bacterial spores, fungi, and viruses in approx. 15 min
Autoclaving
Process of autoclaving
items placed in the chamber, air is evacuated by a vacuum pump, and steam is forced into the chamber at a high temperature
things that can be sterilized by autoclaving
medical waste
infectious materials
culture media
surgical tools
lab glassware
reduces the chances of spoilage and disease in milk
Pasteurization
what is not affected by pasteurization?
bacterial SPORES
traps microorganisms
Filtration
why is filtration useful?
it is useful for sterilizing liquids that can be destroyed by heat
how does filtration work?
organisms above a certain size threshold are trapped in the pores of the filter
types of radiation
UV
Ionizing
Crosslinks nucleic acids rendering organism unable to replicate genetic material
UV Radiation
X-ray, Gamma-ray, or microwave radiation create strand breaks in in nucleic acids rendering organism unable to replicate genetic material
Ionizing radiation
pros and cons of radiation
active against spores but they can have resistance to low level radiation
Physical methods of food preservation
Drying (removes water)
Salting/curing (removes water through osmosis)
Low temps (lower microbial growth rates)
chemical agent the is used to kill microbes on living tissue
Antiseptics
chemical agents that is used to kill microbes on a non-living surface
Disinfectants
High-level disinfectants
Hydrogen peroxide
Chlorine
Chlorine dioxide
Gas vapor
Mid-level disinfectants
Alcohol
Iodine
Low-level disinfectants
Quartenary Ammonium compounds
Soap and Hot Water
How does hydrogen peroxide destroy cells?
destroys proteins and membranes
How does chlorine destroy cells?
highly reactive oxidizer
destroys proteins, membrane, and nucleic acids
How does gas vapor destroy cells?
disrupting protein functions
Chemical disinfectants that are effective against spores
Hydrogen peroxide
Chlorine dioxide
Chlorine
How does alcohol destroy cells?
disrupts membrane bi-layers
How does idoine destroy cells?
disrupts protein function and enzymes
(oxidizes essential enzymes)
neutrophile pH
5-8 (most human pathogens)
acidophile pH
0-5
alkaliphiles pH
9-11
what happens when cells are placed in pH conditions below the optimum?
protons can enter the cell and lower the internal pH to lethal levels
How do cells prevent the influx of protons from low pH conditions?
exchange extracellular K+ for intracellular H+ (protons)
the diffusion of fluid through semi permeable membrane from an area of low solute concentration to an area of high solute concentration
osmosis
how do quartenary ammonium compounds kill cells?
disrupts membrane bi-layers
prevents bacteria from dividing
how does soap and hot water kill cells?
Molecules of soap disrupt membrane bilayers by inserting themselves into membrane but they are not the same shape
things to consider when choosing a chemical agent to clean (5)
- microbial susceptibility to the agent
- temp. and pH
- concentration of the agent needed
- environment (certain areas more sterile than others)
- endospore formers
