Sterilization and Disinfection by Iu8L29JH

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									Sterilization and Disinfection
Sterilization

Process for achieving sterilility.
Sterile

Absence of all viable life forms from an
 inanimate object.

  No degrees of sterility -- An object is sterile or
   it is non-sterile.

  Applies to non-living objects only
Disinfection

Process that leads to the destruction of the
 vegetative cells of pathogens that are on
 an inanimate object.

  Pathogens must be killed but non-pathogens
   may survive
  Spores may survive
  Disinfection and Sterilization are not necessarily
   the same.
Stasis

An inhibition of growth

A static agent inhibits growth of but does
 not kill the target population.
Static Agents

Bacteriostatic -- inhibits bacterial growth

Fungistatic -- inhibits fungal growth.
Cide

To kill

A cidal agent kills the target population.
Cidal Agents

Bactericide -- kills vegetative bacteria
Sporocide -- kills both vegetative
 bacteria and spores
Fungicide -- kills fungi
Virucide -- kills (or inactivates) virus
 particles
Sepsis and Asepsis

Sepsis -- infection

Asepsis -- without infection

Aseptic technique -- process to prevent
 infection
Medical Asepsis

Procedure used to prevent the spread of
 pathogens from one individual to another.
  Aimed at containment
  isolation
  laboratory aseptic technique
Surgical Asepsis

Procedure aimed at the exclusion of all
 organisms from a surgical field.

“Sterile technique”
Methods of Sterilization and
               Disinfection
             I. Physical Methods
1. Boiling
 The method provides for disinfection.
 Process-- Material is boiled at 100°C for 15 to 20
  minutes.
 Mechanism-- Vegetative cells only are killed by
  coagulation (denaturation) of cellular proteins.
 Uses-- The method is effective for disinfection of
  liquids and instruments that can tolerate the
  relatively high temperature.
2. Autoclaving
(steam under pressure)
The method provides for sterilization.
Process-- Material is heated by steam
 under a pressure of 15 psi to reach a
 temperature of 121°C (250°F) which must
 be maintained for 15 minutes. Large packs
 of material may require processing for an
 hour or longer to insure that all material is
 maintained at 121°C for at least 15
 minutes.
Mechanism-- Vegetative cells and spores
 are killed by coagulation (denaturation) of
 cellular proteins.
Uses-- The method is effective for
 sterilization of liquids and instruments that
 can tolerate the temperature. The method
 is not effective for oils, waxes and
 powders because the steam does not
 effectively penetrate such materials.
3. Fractional sterilization
(Tyndallization)
The method provides for sterilization.
Process-- Material is boiled at 100°C for
 15 to 20 minutes per day for three
 consecutive days.
Mechanism-- Vegetative cells are killed by
 coagulation (denaturation) of cellular
 proteins. Spores capable of germination
 should have done so by the third day. Any
 remaining spores are considered to be
 non-viable and thus incapable of
 germination.
Uses-- The method is not commonly used
 except for liquids.
4. Incineration (flaming)

The method provides for sterilization.
Process-- Material is burned to ashes.
Mechanism-- Vegetative cells and spores
 are killed by coagulation and oxidation of
 cellular proteins.
Uses-- In addition to sterilization of
 inoculating loops, the method is primarily
 used for the terminal sterilization of
 disposable, burnable materials (paper and
 plastic). One caution with the method is
 that the material must be completely
 burned leaving no pockets of unburned
 materials which may contain viable
 organisms.
5. Dry heat sterilization
(hot air oven)
a. The method provides for sterilization.
b. Process-- Materials are baked in an
 oven at either 160°C for 2 hours or 170°C
 for 1 hour.
c. Mechanism-- Vegetative cells and
 spores are killed by desiccation and
 coagulation of cellular proteins.
 Uses-- This is the preferred method for
 the sterilization of oils, waxes and
 powders. The method does produce
 charring of paper if materials are paper
 wrapped.
6. Pasteurization

The method provides for disinfection.
Process-- Liquid material is heated to
 72°C for 15 seconds.
Mechanism-- Vegetative cells of
 pathogens and some nonpathogens are
 killed by coagulation of cellular proteins.
Uses-- The method is used primarily for
 liquids such as milk and beer.
7. Filtration

The method provides for sterilization.
Process-- Liquid or gas is forced through a
 filter having an average pore diameter of
 0.1 µm to 0.01µm.
Mechanism-- Microorganisms which are
 too large to pass through the filter pores
 are trapped on the filter surface. Of
 course, any microorganism which is
 smaller than the pore diameter will pass
 through the filter.
Uses-- The method is suitable only for
 liquids or gases.
8. Refrigeration

The method provides for stasis.
Process-- Material is stored at a
 temperature of 4°C.
Mechanism-- The rate of various metabolic
 pathways is slowed; therefore, the
 generation time of the organisms is greatly
 increased. Most organisms are not killed
 but are preserved.
Uses-- The method is an effective means
 of preservation.
9. Freezing

The method provides for stasis.
Process-- Materials are stored at -20°C to
 -60°C.
Mechanism-- Similar to refrigeration but
 the organisms are prevented from
 multiplying.
Uses-- Preservation of cultures is the
 principle use.
10. Lyophilization (freeze drying)
The method provides for stasis.
Process-- Materials are quickly frozen then
 placed in a vacuum chamber where the
 water is then drawn off by sublimation. .
Mechanism-- Without water cellular
 metabolism is impossible.
Uses-- This method is the preferred
 method for the preservation of all types of
 microorganisms.
11. Desiccation
The method provides for stasis.
Process-- Materials are dried at 45 C for
 24 hours.
Mechanism-- Water is removed resulting
 in plasmolysis of the cytoplasmic
 membrane. Organisms which are in the
 plasmolyzed state cannot multiply.
Uses-- The method is rarely used as a
 means of preserving microorganisms.
12. Osmotic pressure

The method provides for stasis.
Process-- Material is placed in a
 hypertonic medium.
Mechanism-- Water is removed resulting
 in plasmolysis of the membrane.
Uses-- The method is rarely used as a
 means of preserving microorganisms.
13. Ionizing radiation
The method provides for sterilization.
Process-- Material is bombarded with
 either X-rays, gamma rays, or a high
 energy electron beam.
Mechanism-- Vegetative cells and spores
 are killed by DNA disruption.
Uses-- Materials which cannot withstand
 high temperatures such as disposable
 plastic supplies.
14. Ultraviolet radiation

The method provides for disinfection.
Process-- Material is directly exposed to
 ultraviolet radiation.
Mechanism-- DNA is altered by the
 formation of thymine dimers which inhibit
 DNA replication.
Uses-- The process is limited to
 applications such as disinfection of
 surfaces and liquids which are directly
 exposed to the ultraviolet source.
Methods of Sterilization and
               Disinfection
            II. Chemical Methods:
1. Phenol and the phenolic compounds

The agents provide for disinfection.
Mechanism-- Vegetative cells are killed by
 cytoplasmic membrane disruption and
 coagulation of proteins.
Examples-- phenol (carbolic acid);
 hexachlorophene; O-phenylphenol
2. Halogens

-- Iodine and iodophore compounds:
Iodophores (such as povidone-iodine) are
  composed of elemental iodine bound to an
  organic carrier molecule
  (polyvinylpyrrolidone) which slowly
  releases the iodine.
The agents provide for disinfection.
Mechanism-- Vegetative cells are killed by
 coagulation of proteins.
Iodine Examples -- Tincture of iodine;
 Betadine; Isodine
-- Chlorine and chlorine compounds:
The agents provide for disinfection.
Mechanism-- Vegetative cells are killed by
  coagulation of proteins.
Chlorine Examples-- Chlorine gas; Clorox
  and other hypochlorite bleaches (NaClO)
3. Alcohols
(ethyl and isopropyl alcohol)
The agents provide for disinfection.
Mechanism-- Vegetative cells are killed by
 coagulation of proteins as well as
 dehydration and lipid solvation.
Examples-- Ethyl alcohol and isopropyl
 alcohol used in concentrations of 70%(v/v)
 to 90%(v/v).
The alcohols exhibit reduced efficacy as
 disinfectants when used at concentrations
 above 90%(v/v).
At concentrations below 45%(v/v), the
 alcohols are ineffective as disinfectants.
4. Heavy metal compounds
 The agents provide for disinfection when used
  in high concentrations and stasis when used in
  low concentrations.
 Mechanism-- When used in high concentrations,
  the agents kill vegetative cells by enzyme
  denaturation. When used in low concentrations,
  the agents produce enzyme inhibition.
 Examples-- Mercurochrome; merthiolate; silver
  nitrate; mercury bichloride
5. Surfactants
(soaps and detergents)
The agents provide for disinfection.
Mechanism-- The agents cause
 cytoplasmic membrane disruption.
Examples-- Zephiran and other quaternary
 ammonium compounds
6. Organic and mineral acids

The agents provide for disinfection.
Mechanism-- The agents produce protein
 coagulation.
Examples-- Calcium propionate; acetic
 acid; esters of benzoic acid
7. Alkylating agents

-- Formaldehyde:
The agent provides for disinfection when
  used as a solution (formalin) or
  sterilization when used as a gas.
Mechanism-- This agent produces protein
  coagulation.
-- Glutaraldehyde:
The agent provides for either sterilization
  or disinfection depending upon the
  concentration.
Mechanism-- This agent produces protein
  coagulation.
Example-- Cidex
-- Ethylene oxide gas:
The agent provides for sterilization.
Mechanism-- This agent produces protein
  coagulation.
8. Oxidizing agents

The agents provide for disinfection.
Mechanism-- The agents provide for
 oxidation of cellular proteins.
Examples-- Ozone; hydrogen peroxide;
 benzoyl peroxide;
 potassium permanganate

								
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