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37 Cards in this Set
- Front
- Back
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What properties of Cryptosporidium parvum make it difficult to remove from water supplies?
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C. parvum has thick walled oocysts that are highly resistant to chlorine.
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Sterilization
Chemicals that kill micoo=GERMICIDES |
Is a treatment that destroys all life. Completely eliminates all micoo including viruses
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Disinfection/Sanitation
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Reduces the number of pathogens to a safe level.
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Decontamination
Germicides that are used on inanimate objects= DISINFECTANTS |
Renders an instrument or surface that has been heavily exposed to microo safe.
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Antisepsis
Germicides applied to living tissue = ANTISEPTICS |
Treats living tissue to destroy or inhibit microbial growth
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What is the method of determining whether a cell is alive or dead?
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Microbial death cells cannot divide or form new colonies.
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How do the # of cells decrease with time of exposure to a lethal treament?
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Cells die exponentially(not all at the same time)Straight line when plotted on a logarhytm scale.
# of surviving cells decreases by 1 logarhtym during each unit of time called D value. |
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D Value
HOW LONG IT TAKES TO KILL 90% OF THE MICROO POPULATION |
Decimal reduction time= The time in minutes it takes to kill 90% of the cells in a population. Add a D value and 90% of the surviving cells will die.
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Microbiostatic
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Treatments INHIBIT (prevent) growth
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Microbiocidal
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Treatments KILL microbial cells
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Thermal Death Point(TDP)
TEMPERATURE |
Is the LOWEST temperature required to kill all microo in a liquid suspension in 10 minutes.
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Thermal Death Time (TDT)
TIME |
Is the MINIMAL TIME required to kill all microo in a liquid suspension at a given temperature
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What do you need to know to design a sterilization treatment?
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1. D-value
2. # of cells to be eliminated 3. Desired degree of certainty that no cells will be left alive |
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How does heat kill?
What is the advantage of heat over other sterilization treatments? Heat is most effective method and it sterilizes beyond just the surface. |
Heat penetrates through out the object to kill micoo by denaturing protein.
Can be dry(direct flaming) Can by moist(boiling, oven, autoclaving) |
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How is cold a microbiostatic treatment?
Refrigerator 5 degrees |
Slows or stops miccoo growth.
Preserves perishable materials including food & micoo. Exception Psychrophiles |
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How does freezing kill bacteria?
Rapid freezing can preserve bacterial cultures. |
Freezing kills most bacteria, but survivors remain alive for long period in a frozen state.
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What are the two forms of radiation? How do they act?
Only exposed surfaces are sterilized |
Ultraviolet (UV)Damages DNA light /ionizing radiation (X-ray/ gamma rays) strips electrons from atoms
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How does filtration control micoo?
Does filtration sterilize? |
Filtration physically removes microbes.
It CANNOT sterilize because viruses pass through filters. |
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How does high osmotic strength control micoo?
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Drying removes an essential nutrient water.
Increase osmotic strength by adding salt or sugar(preserves food). |
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What to ask when choosing a germicide?
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1. Will it damage the object being treated?
2. Will it control the target micoo? 3. Is the purpose to contol OR eliminate all micoo |
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How do you determine a phenol coefficient?
End point of dilution is 1:1000 and phenol is 1:100;the germicide's phenol coefficient is 10 (1000 divided by 100)=10 |
The highest dilution of the germicide that kills in 10 but not 5 minutes is the end point. The ratio of end points is the phenol coefficient.
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Explain paper disc method.
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The size of a bacteria-free zone around a disc with germicide indicate its effectiveness.
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Explain the use-dilution test for determing the effectiveness of a germicide.
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1. The test organism is added to dilutions of the germicide.
2. Tubes are incubated. 3. The highest dilution of the germicide that remains clear indicates effectiveness. |
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How are germicides classified?
Presence of substances, blood, feces, diminishes effectiveness of germicide |
High
Intermediate Low germicidal activity. |
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Phenol
Phenolics also act on lipids |
Compound w/hydroxyl group w/ attached benzene ring
DENATURE PROTEIN |
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Hexachlorine
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Antiseptic very toxic to humans. Absorbed through skin passed to infants.
Chlorhexide used now |
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Cresols
Paracresol |
Household/ hospital disinfectants
Remain active w/ blood/feces Lysol |
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Alcohols
DO NOT KILL ENDOSPORES Disinfect sites for injection or for drawing blood Disinfect thermometers |
Compounds with hydroxyl -OH) group
DISRUPT THE LIPIDS IN CELL MEMBRANE AND DENATURES PROTEINS. 1. They dissolve lipids on skin 2. Expose micoo 3. Kill them |
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Halogens
Iodine- Antiseptic before surgery/ sterilize dairy equ. Chlorine-Disinfectant |
INACTIVATE PROTEINS(Enzymes included) by
OXIDIZING THEIR FUNCTIONAL GROUPS |
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Hydrogen peroxide
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Does minimal damage to fragile objects
Weak antiseptic-clean wounds disinfect medical instruments Soft contact lenses. |
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Heavy Metals Silver Salts
Eyes of newborns prevent ophthalmic gonorrhea- Now antibiotics |
Sulfhydryl (-SH) Reacts w/ proteins of micoo and poisoning enzymes.
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Surfactants
Soaps/ detergents Good for frequent hand washing |
Compounds w/hydrophilic/phobic parts.
They penetrate oily substances in water. Make emulsion so it can be washed away. |
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Alkylating agents
Formaldehyde-Preserves tissues, preapares vaccine, sterilize surgical instruments Glutaraldehyde Ethylene oxide-Gas form sterilize heat sensitive material or matresses. |
Inactivates enzymes by adding alkyl groups.
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Why does food spoil despite refrigeration?
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Psychrophilic micoo not killed by 5 degree temperature. They continue to grow spoiling food.
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What is the benefit of pasteurization?
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Heat treatment that controls micoo w/out sterilization and with minimal effect on the food.
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What determines safe heat treatments for canning?
Botulism |
Canning procedures are designed to ELIMINATE with a HIGH degree of assurance all spores of C. botulinum
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Explain why salting and drying food are effctive preservation methods.
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REMOVE WATER which is essential for micoo.
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