Sterilization -
Sterile-
- process that destroys or removes ALL viable organisms
- critical objects and noncritical items require sterilization
-the absence of absolutely ALL viable microbial life
reserved for inanimate objects because it would be dangerous if preformed on living tissues
Disinfection-
Disinectant-
- a process that destroys all viable microbes including viruses and endosores
- semi-critical objects and noncritical items require disinfection
-destroys vegetative pathogens but not bacterial endospores
sanitization
any cleansing technique that meachanically removed microbes
ex)
soaps, detergents
degaermation
reduces the number of microbes through mechanical means
ex)
surgical handscrub, alcohol whipes, germical soaps
microbial agents
agents that cause microbistasis
microbistasis
microbes are temporarily prevented from multiplying but are not killed
microbicide (germicide)
any chemical agents that kill pathogenic microorganisms
end in (-cide)
modes of action
- the cell wall
- the cell membrane
- protein and nucleic acid synthesis
- proteins
effects of agents on cell wall
a cell derived of a functioning cell wall becomes fragile ans lysed
ex) ~agents~
detergents, alcohol
effects of agents on cell membrane
cell loses selective permeability and cannor prevent loss of vital moleculed> death
ex) ~agents~
detergent surfactants
effects of agents of protein and nucleic acid synthesis
blocked process of replication, transcription, translation result in some mutations
ex)
uv radiation
effects of agents on protein function
denatured proteins. misfolding
loss of normal protein function can arrest metabolism and exert broad effects on microbes
ex)
alcohols, phenols, acids, heat
denaturization can occur via coagulation by moist heat
effects of agents on protein function
denatured proteins. misfolding
loss of normal protein function can arrest metabolism and exert broad effects on microbes
ex)
alcohols, phenols, acids, heat
denaturization can occur via coagulation by moist heat
microbial death (detemination)
Nonviable if microbial cell sustains metabolic/structural damage to an extent that it can no longer reproduce
factors that affect death rate
- legnth of exposure
- effects of microbial load(quantity)
- resistance of endospores
- action of agent (microbicidal or microstatic)
note:
agents target a cell’s metabolic process *active cells die more rapidly
highest resistance:
moderate resistance:
least resistance:
(highest)
prions:
-protenaceous infectious particles
-bacterial endosores
bacillus and clostridium
(moderate)
-protozoan cysts:
-some fungal spores
-some viruses
-naked virusrs
mycobacterium, pseudomonas, staphylococcus
(low)
bacterial vegetative cells
fungal spores
hyphae
enveloped viruses
yeast
protozoan trophozoitesmethods of physical control
- heat (moist and dry)
- cold temperatures
- Disiccation
- Radiation
- Filtration
moist heat
- moist heat
- boiling water
- pastirization
(moist heat)
- lower temperatures and shorter exposure time
- coagulation and denaturation of proteins
(pressurized steam)
-Sterilant
-AUTO-CLAVE
(nonpressurized steam)
-TYNDALYZATION- intermediate sterilant(boiling water)
-disinfection
(pastirization)
- Disinfection - kills nonendosporeforming pathogens - doesn't kill endospores or nonpathogenic microbes - uses FLASH METHOD - targets salmonella, brucella, lysteria monocytogenes
Dry Heat
- incineration - desication - cold
(dry heat)
- moderate to high temps
- dehydration, alters protein structures, incineration
- lack of water increases stability of some protein conformations
(incineration)
-ignites and reduces microbes and other substances
(desication)
-dehydrated
(cold)
-MICROSTATIC
-slows microbe growth
ex)
s. aureus, clostridium, listeriaRadiation
(Radiation)
-energy emmited from atomic activities and dispersed at high velocity through matter and space
(modes of action)
>ionizing
-energy rejects electron from an atom
-gamma rays, x-rays, cathode rays
>nonionizing
-excited atom by raising to higher energy state
-formation of double bonds
-mutations
-UV rays
Ionizing Radiation
(cold radiation & irradiation)
ex)
-gamma rays, x-rays, cathode rays
- sterilant
- preserving food
> benefits
- 50%fewer infections and deaths
- can sterilize sensitive materials
- more penetrating than nonionizing radiation
> disadvantages
-factory exposure to radiation
Non-ionizing Radiation
ex)
-UV rays
- disinfection
- sterilizing air, water, or surfaces
- as UV passes through a cell it is readily absorbed by pyrimidine bases»_space;forming pyrimidine dimers
- pyrimidine dimers interferes with normal DNA Replication, and transcription»_space;> lead to inhibition of growth and cellular death - produces free radicals(toxic photochemicals)
- free radicals bind to DNA, RNA, or proteins»interfere with essential cell processes
> disadvantages
- UV has poor powers of penetrating solids
- UV has damaging effects on human tissues
Filtration
- physical removal of microbes passing through a gas or liquid through a filter
- sterilize heat sensitive liquids and air
ex)
blood products, vaccines, drugs, enzymes
Levels of decontamination
(High-level germicide)
- Sterilants
- not heat sterilizable and intend to be used in sterile environments (body tissues)
(Intermediate-level germicide)
- disinfectants
- kill fungal spores, tubercle bacillus, viruses
- disinfect contact with mucous membranes, but not invasive
(Low-level germicide)
- eliminate only vegetative bacteria
- clean surfaces that touch skin but not mucous membranes
