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40 Cards in this Set

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Sterilization
- Destruction of all microbes, including endospores.
- Usually done by steam under pressure, or sterilizing gas
Sanitization
- Treatment that lower microbial counts to safe levels for public health purposes
- high temperature washing, or soaking in a chemical disinfectant.
Disinfection
- Destruction of vegetative pathogens
- physical or chemical methods --> Kills > 3 logs (decrease by 3 orders of magnitude)
Decontamination
- Reduction of pathogenic microbes to a levels where items are safe to handle.
- Elimination of Debris by cleaning.
- Prerequisite before disinfection of sterilization.
Antisepsis
- Destruction of vegetative pathogens on living tissue
- Always done with chemical antimicrobials.
Parameters affecting disinfection/sterilization efficiency (4)
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)
Why are vegetative cells more vulnerable?
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
Why are spores harder to kill?
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.
Rate of microbial death by temperature is ____.
constant --> logarithmic
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
___ surrounded by ____ are most susceptible to disinfectant due to their changing ____.
viruses ... lipids... fluidity
____ have low level resistance to disinfectants.
Vegetative (proliferative, metabolically active) bacteria
____ have intermediate levels of resistance to disinfectants due to their proteins being ____ and low amounts of ____.
non-lipid viruses... crystal-like... water
____ have high level resistance to disinfectants for _____ reasons.
Mycobacteria .... unknown
____ are sterilants due to their ___ metabolic activity.
Spores... low
3 ways to estimate death by heat
1) Thermal death point (TDP)
2) Thermal death time (TDT)
3) Decimal reduction time (D value)
Thermal death point (TDP)
lowest temperature at which all the microorganisms in a liquid suspension will be killed in 10 minutes
Thermal death time (TDT)
minimal length of time at which all bacteria in a liquid suspension wilol be killed at a given temperature
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.
T/F - D-value depends on initial concentration
False
(4)Physical methods of microbial control
Filtration
Irradiation
Cold
Heat
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.
Physical methods of microbial control 2

Cold
Bacteriostatic!!!

Note: some bacteria do grow in the cold, but slowly.
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
hot air sterilization: heat in oven @ ___ for ___ hours
170 C ... 2
Physical methods of microbial control 4

Moist heat (3 types)
Moist heat: denaturation of macromolecules
-Pasteurization
-Boiling
-autoclave
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
Moist heat 2

Boiling
kills all vegetative forms of pathogenic bacteria and fungi within 10 minutes.
Moist heat 3

Autoclave
heating under pressure to temperatures above boiling.
121 C for 15 mins will kill ALL microbial forms.
T/F- Moist heat is a more efficient sterilization method than dry heat
True
H2O in the sample can change conformation of molecules
Destruction of prions
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
____ (3) alter membrane permeability.
alcohols
anionic detergents
phenols (at low conc.)
____ (8) damages proteins and nucleic acids.
aldehydes
biguanides
chlorine compounds
iodophors
oxidizing compounds
phenols (at high conc)
quaternary ammonium compounds
acridines
Inhibition of membrane potentials / electron transport chain can be caused by _____ (3)
bis-phenols
heavy metal derivatives
organic salts
___ 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 ______.
Disinfectant
Glutaraldehyde
alkylates.
disinfect medical eqiupment
____ is a strong oxidizer that attaches to ____ (3). It has ___ levels of toxicity to humans. It acts as a ___
H2O2
lipids, DNA, and proteins
low
disinfectant
___ is the most commonly used antiseptic. ___ enhances its activity and helps it denature ____.
Alcohol
H2O
Proteins
____ 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.
Iodophors
I2
blood
Slowly
longer
Alcohol & Iodophors are useful against____. They both act pretty ____.
Bacteria, fungi and viruses
rapidly (alcohol > iodophors)
___ & ___ are used in hospitals before surgery to wash hands. Both have little effect on fungi.
Tricloxan (no effect on viruses)
Chlorohexidine