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Disinfection & Sterilization, GK Notes ! :fountain…
Disinfection
& Sterilization
Physical
Sunlight
Radiation
Ionizing
particulate
Electron beams
electromagnetic rays
gamma rays
Non-ionizing
Ultraviolet (UV)
Infrared rays
Filtration
Earthenware filters
Asbestos filters
Sintered glass filters
Air Filters
High Efficiency Particle Air / HEPA filters
Membrane filters
Syringe filter
Vibration
Sonic & Ultrasonic
Heat
Dry heat
Incineration
Hot air oven
Flaming
Red heat
moist heat
At temperature below 100oC
Pasteurization
Flash method (72ºC for 20 sec
followed by cooling to 13ºC).
Holder method (63ºC for 30 min)
Vaccine bath
Serum bath
Inspissation (Fractional sterilization)
At temperature 100oC
Boiling
Tyndallization or intermittent sterilization
Steaming
At temperature above 100oC
Autoclave
simple non-jacketed laboratory
Steam-jacketed downward displacement
High pressure pre-vacuum
Physio-chemical
Steam formaldehyde
Chemical
Classification of disinfectant Based on
mechanism of action
Action on membrane (E.g., Alcohol, detergent)
Denaturation of cellular proteins (E.g., Alcohol, Phenol)
Oxidation of essential sulphydryl groups of enzymes (E.g., H2O2, Halogens)
Alkylation of amino-, carboxyl- and hydroxyl group (E.g., Ethylene Oxide, Formaldehyde)
Damage to nucleic acids (Ethylene Oxide, Formaldehyde)
consistency
Liquid (E.g., Alcohols, Phenols)
Gaseous (Formaldehyde vapor, Ethylene oxide)
spectrum of activity
Low level
Alcohols
quaternary
ammonium compounds
High level
Ethylene Oxide,
Gluteraldehyde,
Formaldehyde
Intermediate level
Halogens
Phenolics
Examples
Alcohols
: Ethyl alcohol, isopropyl alcohol
Aldehydes:
Formaldehyde, glutaraldehyde, Ortho-phthaladehyde
Phenolic compounds
: Cresol, lysol, chlorhexidine, chloroxylenol, hexachlorophene
Halogens:
Chlorine, iodine, iodophors
Oxidising agents
: Hydrogen peroxide, Peracetic acid
Salts
: Mercuric chloride, copper salts
Surface active agents:
Quaternary ammonium compounds and soaps
Dyes
: Aniline dyes and acridine dyes
Gas sterilization
: Low temperature steam formaldehyde, Ethylene oxide (ETO) and Betapropiolactone
Ideal properties of antiseptic or disinfectant
wide spectrum of activity
able to destroy microbes within practical period of time
active in the presence of organic matter
make effective contact and be wettable
active in any pH
stable
long shelf life
speedy
high penetrating power
non-toxic, non-allergenic, non-irritative or non-corrosive
no bad odour
not leave non-volatile residue or stain
Efficacy should not be lost on reasonable dilution
not be expensive and must be available easily
Factors Influencing
• Organism load
• Nature of organisms
• Concentration
• Temperature
• Nature of the sterilant/disinfectan
• Duration of exposure
• pH
• Biofilm formation
GK Notes
! :fountain_pen:
