Download Sterilization

Sterilization
Sterilization
 It is the process that destroys all microorganisms (including
bacterial microspores).
 The skin could never be sterilized without its own destruction.
Disinfection
 A process which destroys only the vegetative forms of organisms
=basically clean.
 A disinfectant (germicide, antiseptic): any chemical substance
with either a bactericidal or a bacteriostatic action.
 Antiseptic -- Agent applied to living tissue
 Disinfectant -- Agent applied to inanimate surface
Methods of Disinfection
 Physical: The most important as they can be relied on to ensure
the sterilization of articles used in the treatment of patients:
– Thermal: Heat or Steam
– Radiation: infra-red radiation, - rays,  particles
– Filtration: utilizing filters capable of screening out
microorganisms
 Chemical: Less effective, used for personnel
– Organic
– Inorganic
 Gaseous disinfectants: very efficient, not routine
– Formaldehyde gas
– Ethylene oxide
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Sterilization
Physical Methods of Disinfection HEAT
DRY HEAT
 Kills by Destructive oxidation of cell constituents
 Surest incineration
 Hot-air oven:
– inefficient, poor conductor of heat, penetrates feebly.
– 160°C for 1 hour: damages fabrics, melts rubber
– Used for: Glassware, oily fluids, powders
Physical Methods of Disinfection HEAT
MOIST HEAT
Effective at low temperature, in a shorter period of time
 Boiling: 100°C for 30 minutes
 Pasteurization: 63°C for 30 minutes
 Tyndallisation: steaming for 20 minutes for 3 successive days
 Steaming under pressure= Autoclaving
Advantages of steam
 Kills by denaturing & coagulating enzymes & proteins
 More rapid (maximum needed time 45mn) & at lower
temperature
 Condensation of steam leads to liberation of latent heat which
raises the temperature, and gives more penetration
 Half dense as air, so has better penetration
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Sterilization
RADIATION DISINFECTION
 High energy ionizing radiation destroys microorganisms and is
used to sterilize prepacked, Single-use, surgical equipment by
manufacturers
 Common sources of radiation include electron beam and Cobalt60
CHEMICAL DISINFECTION
A SATISFACTORY AGENT SHOULD:
 Be active against a wide range of organisms and spores. Only few
are truly sterilizer
 Have a rapid action
 Should not be toxic or irritant to the skin
 Should be Persistent
There is no one disinfectant which can be used to kill all
micro-organisms in all situations.
Types of Chemical disinfectants
 Inorganic:
– Iodine
– Chlorine
 Organic:
– Alcohols
– Aldehydes
– Phenols
– Cationic surface-active agents
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Sterilization
Inorganic disinfectants
The halogens: Chlorine and Iodine
 Have a rapid action against vegetative organisms and spores=
true sterilizers
 Their action is annulled by foreign organic material
Iodine disinfectants
The broadest spectrum of all topical anti-infectives, with action
against bacteria, fungi, viruses, spores, protozoa, and yeasts.
 Tincture iodine:
– 2.5% iodine & 2.5% potassium iodide in 90% ethanol.
– Best skin disinfectant
– Irritating to raw surfaces: due to its alcoholic component
– Allergic dermatitis
 Iodophors: Solutions of iodine in non-ionic detergents= Povidone
iodine= Betadine
– Less irritating and less staining
– Less disinfectant than tincture
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Sterilization
Chlorine disinfectants
 Powerful, Disinfect water
 Particularly active against viruses
 Concentrated solutions too corrosive
 Usually diluted with a compatible detergent
Organic Disinfectants
 Alcohols: bactericidal: 50-70% ethanol
 Aldehydes:
– Formalin: irritant, powerful=sterilizer
– Glutaraldehyde: less irritant, not volatile, more rapid action.
 Phenols: continued activity in organic matter as human excreta.
– Phenol: Toxic, expensive
– Cresols: Lysol
– Chloroxylenol: Dettol
– Chlorhexidine: Hibitane- Alkanol
– Hexachlorophene
 Cationic surface-active agents:
– Cetrimide: Cetavlon
Alcohol
 Isopropyl Alcohol 70% (or Ethyl Alcohol 90%)
ADVANTAGES:
 Causes protein denaturation, cell lysis, and metabolic interruption.
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Sterilization
 Degreases the skin.
DISADVANTAGES:
 Ineffective against bacterial spores and poorly effective against
viruses and fungi.
Chlorhexidine Gluconate Hibitane vs Alkanol
Broadest spectrum
Better residual activity than Iodophors
Occasional skin sensitivity
ADVANTAGES:
Rapid action
Residual activity is enhanced by repeated use
Less susceptible to organic inactivation than povidone iodine
DISADVANTAGES:
Occasional skin sensitivity.
Inactive against bacterial spores
Activity against viruses and fungi is variable and inconsistent
May harm metal instruments
Gaseous Disinfection
Ethylene Oxide Sterilization: EO Gas
 Colorless gas, available as cartridges
 Toxic and flammable, Odor similar to ether
 Has an extremely well penetration, even though plastics
 Microorganism destruction is caused by a chemical reaction
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Sterilization
 Effective sterilization is dependent on concentration of gas, exposure
time, temperature, and relative humidity
 Powerful sterilizer: Kills all known viruses, bacteria (including
spores), and fungi
EO Gas Sterilizer
 Is used in large hospitals, as it is expensive, dangerous, needs more
expertise.
 Used for heat sensitive instruments: fabrics, plastics, suture material,
lenses, endoscopes, electrical equipment and finely sharpened
instruments.
 At 20°C-25°C: sterilization takes 18hours
 At 50°C-60°C: sterilization takes 4 hours
 In Demerdash: The average of the cycle is 8-14 hours
Practical Sterilization Instruments sterilization
 Metal Instruments: Avoid chemical sterilization
– Autoclave
– EO chamber
– Formaldehyde beads or powder
 Sharp-edged: avoid heating & wetting:
– EO chamber
– Formaldehyde beads or powder
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Sterilization
Practical Sterilization Instruments sterilization
 Catheters, gloves,…: depend on pre-sterilized, disposable equipment
– Radiation
– EO chamber
 Endoscopes: avoid heat
– Cidex
– Lysoformin
– Autoclaving
 Handles of drills:
– Autoclave after washing and oiling
– EO chamber
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