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40 Cards in this Set
- Front
- Back
Sterilization
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- Destruction of all microbes, including endospores.
- Usually done by steam under pressure, or sterilizing gas |
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Sanitization
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- Treatment that lower microbial counts to safe levels for public health purposes
- high temperature washing, or soaking in a chemical disinfectant. |
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Disinfection
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- Destruction of vegetative pathogens
- physical or chemical methods --> Kills > 3 logs (decrease by 3 orders of magnitude) |
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Decontamination
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- Reduction of pathogenic microbes to a levels where items are safe to handle.
- Elimination of Debris by cleaning. - Prerequisite before disinfection of sterilization. |
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Antisepsis
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- Destruction of vegetative pathogens on living tissue
- Always done with chemical antimicrobials. |
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Parameters affecting disinfection/sterilization efficiency (4)
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1) Bacterial strain and form (vegetative -easier to kill vs. spore- harder to kill)
2) temperature (higher temp --> faster & more efficient killing) or disinfectant concentration 3) treatment duration (longer the treatment --> better chance to kill them) 4) initial concentration of cells and spores (easier to kill less) |
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Why are vegetative cells more vulnerable?
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Vegetative cells or proliferating cells are doing DNA synthesis --> @ replicating fork there is single stranded DNA --> not protected by proteins --> vulnerable to mutations and breaks
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Why are spores harder to kill?
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Spores have a low H2O content --> high concentration of molecules in the cell and they become like crystals --> harder to denature
They are non-proliferating. |
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Rate of microbial death by temperature is ____.
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constant --> logarithmic
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The ____ is important when considering microbial killing.
___ starting [] will end up with 0 cells faster than populations with _____ starting [] but both populations can be killed at the same rate. |
initial concentration of cells
Lower ... higher |
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___ surrounded by ____ are most susceptible to disinfectant due to their changing ____.
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viruses ... lipids... fluidity
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____ have low level resistance to disinfectants.
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Vegetative (proliferative, metabolically active) bacteria
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____ have intermediate levels of resistance to disinfectants due to their proteins being ____ and low amounts of ____.
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non-lipid viruses... crystal-like... water
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____ have high level resistance to disinfectants for _____ reasons.
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Mycobacteria .... unknown
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____ are sterilants due to their ___ metabolic activity.
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Spores... low
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3 ways to estimate death by heat
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1) Thermal death point (TDP)
2) Thermal death time (TDT) 3) Decimal reduction time (D value) |
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Thermal death point (TDP)
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lowest temperature at which all the microorganisms in a liquid suspension will be killed in 10 minutes
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Thermal death time (TDT)
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minimal length of time at which all bacteria in a liquid suspension wilol be killed at a given temperature
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Decimal reduction time (D value
MOST IMPORTANT!! |
time in which 90% of population will be killed at a given temperature. Gives accurate means to estimate how long and at what temp need to destroy an microorganism. Used in hospitals.
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T/F - D-value depends on initial concentration
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False
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(4)Physical methods of microbial control
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Filtration
Irradiation Cold Heat |
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Physical methods of microbial control 1
Irradiation (2 forms) |
1) ionizing (gamma, X)- H2O-->hydroxyl radicals --> react with biological moelcules --> DNA!! High penetration
2) non-ionizing (UV)- absorbed and modifies DNA. Low penetration. |
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Physical methods of microbial control 2
Cold |
Bacteriostatic!!!
Note: some bacteria do grow in the cold, but slowly. |
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Physical methods of microbial control 3
Dry Heat (2 methods) |
Oxidation of macromolecules
- flaming: heating a metal to red glow--> fastest method - hot air: heating in oven |
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hot air sterilization: heat in oven @ ___ for ___ hours
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170 C ... 2
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Physical methods of microbial control 4
Moist heat (3 types) |
Moist heat: denaturation of macromolecules
-Pasteurization -Boiling -autoclave |
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Moist Heat 1
Pasteurization |
heating at 63 C for 30 mins or 72 C for 15 secs --> sufficient to kill most microorganisms that cause food spoilage
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Moist heat 2
Boiling |
kills all vegetative forms of pathogenic bacteria and fungi within 10 minutes.
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Moist heat 3
Autoclave |
heating under pressure to temperatures above boiling.
121 C for 15 mins will kill ALL microbial forms. |
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T/F- Moist heat is a more efficient sterilization method than dry heat
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True
H2O in the sample can change conformation of molecules |
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Destruction of prions
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need high temp to completely denature because they are very stable structures.
133 C for 120-240 mins 180 C (dry heat) for 24 hrs |
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____ (3) alter membrane permeability.
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alcohols
anionic detergents phenols (at low conc.) |
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____ (8) damages proteins and nucleic acids.
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aldehydes
biguanides chlorine compounds iodophors oxidizing compounds phenols (at high conc) quaternary ammonium compounds acridines |
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Inhibition of membrane potentials / electron transport chain can be caused by _____ (3)
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bis-phenols
heavy metal derivatives organic salts |
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___ is a commonly used ____. It is a potent & broad spectrum microbicidal that targets membrane components, nucelic acids, and proteins. It ____ SH, hydroxyl, carboxyl, & amino groups. It is used to ______.
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Disinfectant
Glutaraldehyde alkylates. disinfect medical eqiupment |
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____ is a strong oxidizer that attaches to ____ (3). It has ___ levels of toxicity to humans. It acts as a ___
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H2O2
lipids, DNA, and proteins low disinfectant |
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___ is the most commonly used antiseptic. ___ enhances its activity and helps it denature ____.
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Alcohol
H2O Proteins |
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____ are also commonly used antiseptics. It will release ___. It is less effective in the presence of ____. It is released ___ so it acts for a ___ time.
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Iodophors
I2 blood Slowly longer |
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Alcohol & Iodophors are useful against____. They both act pretty ____.
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Bacteria, fungi and viruses
rapidly (alcohol > iodophors) |
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___ & ___ are used in hospitals before surgery to wash hands. Both have little effect on fungi.
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Tricloxan (no effect on viruses)
Chlorohexidine |