sterilization and disinfection Flashcards
removal or destruction of all forms of life, including bacterial spores
Sterilization
is the most commonly used method for the removal of microorganisms
Heat
It destroys microorganisms by coagulation of enzymes and structural proteins and degradation of nucleic acids
Moist Heat Procedure
It destroys vegetative bacteria (non-sporulating)
Boiling
Temperature and time of exposure of boiling
100 degree celcius for 10-15 minutes
it is a chamber which if filled with hot steam under pressure and is the fastest and simpliest method of sterilization which all organisms (expect prions) and spores are killed within 15 minutes
Autoclave
Principle of Autoclave
Steam under pressure
Biological indicator of autoclave
Geobacillus stearothermophilus
temperature, psi and time for media, liquids, utensils, glass pipettes and instruments for assay
121 degree celsius, 15 psi for 15 minutes
temperature, psi and time for decontaminating medical waste
132 degree celsius, 15 psi for 30-60 minutes
temperature and time of exposure of fractional/ intermittent sterilization (tyndallization)
100 degree celsius for 30 minutes (3 consecutive days)
instrument for tyndallization
Arnold’s sterilizer (free flowing system)
it is used to sterilize protein-rich medium such as LJM
Inspissation
Principle of Inspissation
Thickening of media through evaporation
Temp. and time of exposure of Inspissation
70-80 degree celsius for 2 hours (3 consecutive days)
it is used to sterilize milk, dairy products and alcoholic beverages and it eliminates foodborne pathogens and organisms responsible for food spoilage (cannot eliminate bacterial endospores)
Pasteurization/ partial sterilization
Treatment at this temperature reduces spoilage of food without affecting its taste
It destroys milk- borne pathogens
Low temperature Holding/ Batch Method
Temperature and time of exposure of LTH or batch method
63 degree celsius for 30 minutes
temp. and TOE of High temperature short time (HTST) or flash pasteurization
72 degree celsius for 15 seconds (quick heating and immediate cooling)
temp. and TOE of UHT
140 degree celsius for 3 seconds (cooled very quickly in a vacuum chamber)
Advantage of UHT
milk can be stored at room temperature for 2 months without affecting its flavor; applicable also for coffee creamer
it kills microorganism by denaturation of proteins; sterilization without water and it is utilized for the sterilization glassware, oil products and powders
Dry heat procedure
Biological indicator of Dry heat procedure
Bacillus subtilis var. niger
types of dry heat procedure
flaming (direct heating), oven, incineration, cremation
it is used for glassware, oil, petrolatum or powders
oven
temperature and TOE of oven
160 to 170 degree celsius for 1.5 to 2 hours
is the most common method of treating infectious waste and infected laboratory animal
incineration
principle of incineration
burning materials into ashes (300 degrees to 400 degrees)
is used to control the spread of communicable diseases
cremation
it is the method of choice for sterilization of antibiotic solutions, toxic chemicals, radioisotopes, vaccines and carbohydrates (heat sensitive solutions) and it can also be used for both liquid and air
Filtration
2 types of filters
depth filters and membrane filters
it consist of fibrous or granular material
Depth filters
these are porous membranes (almost 0.1 mm thick) composed of cellulose acetate or polycarbonate
membrane filters
types of filtration
liquid filtration, air filtration, filtration of bacteria, yeasts and molds, critical sterilizing
it uses cellulose acetate/ cellulose nitrate membrane with a vacuum
liquid filtration
it uses hepa filters
Air filtration
remove organisms larger than 0.3 micrometer from isolation rooms, operating rooms and biological safety cabinets
Hepa filters
it uses 0.45 micrometer pores of membrane filters
filtration of bacteria, yeasts and molds
range of membrane filters that removes most bacteria as well a fungi, but not viruses
0.2 to 0.45 micrometer
it uses 0.22 micrometer membrane filters for parenteral solutions
critical sterilizing
size of membrane filter used to remove vegetative cells but not viruses
0.22 micrometer
it is considered bacteriostatic because it reduces the rate of metabolism (0 degree to 7 degree celsius) and is important in microbiology
low/cold temperature
destroys bacteria by disruption of metabolism; it involves removing water from microbes (bacteriostatic)
Dessication
is the most effective method for long term preservation of microbial cultures and it destroys bacteria by changes in proteins and decreased chemical reactions
lyophilization
is the use of high concentrations of salts and sugars in food create a hypertonic environment
osmotic pressure
as water leaves the cell, plasma membrane shrinks away from the cell wall (cell may not die, but usually stops growing)
Plasmolysis
principle of radiation
when it passes through the cells, it creates free hydrogen and hydroxyl radicals and some peroxidases which in turn cause diff. intracellular damage
biological indicator of radiation
bacillus pumilus
it causes mutation in DNA and produce peroxides and it destroys vegetative cells and endospores of both prokaryotes and eukaryotes
Ionizaing radiation (cold sterilization)
it causes damage to cellular DNA by producing thymine dimmers
non-ionizing radiation
long wavelength of
> 1nm
ultraviolet rays
10-400 nm (260 nm most lethal)
it refers to removal, inhibition or killing of microorganisms including potential pathogens by using chemical agents usualy inanimate objects
Disinfection
is is applied topically to skin and it inhibits sepsis formation
antiseptic
it is usually applied to inanimate objects
Disinfectant
it precipitates bacterial protein (h2so4, hcl); it kills all bacteria in the specimen
bactericidal
it inhibits the growth of organisms
bacteriostatic
