STERILIZATION TECHNIQUES

DECONTAMINATION

• Combination of processes used to make a re-usable item safe for further use on patients and handling by staff.

DISINFECTION

• Process that kills or removes the pathogenic microorganisms with the exception of bacterial spores.

STERILIZATION

• Process that destroys all forms of microbial life, including bacteria ,virus, spores and fungus

MOST COMMON METHODS OF STERILIZATION

• WET HEAT (Autoclaving)

• ETHYLENE OXIDE.

• DRY HEAT (Flaming, baking)

• LOW-TEMPERATURE STEAM AND FORMALDEHYDE

• FILTRATION

• SOLVENTS

• RADIATION

WET HEAT (AUTOCLAVING)

• The method of choice for sterilization in most labs.

• By using pressurized steam to heat the material to be sterilized.

• Kills all microbes, spores and viruses.

WET HEAT (AUTOCLAVING)

• Kills microbes by hydrolysis and coagulation of cellular proteins.

• Pressurized steam has a high latent heat.• At 100C it holds 7 times more heat than water at the same temperature.

• Heat is liberated upon contact with the cooler surface of the material to be sterilized,

• 15 minutes at 121C.

ETHYLENE OXIDE

• Highly penetrating non corrosive gas that has bactericidal action.

• Used to sterilize heat and moist sensitive materials ,including electrical equipments.

DRY HEAT (FLAMING, BAKING)

• There’s no water, so protein hydrolysis can’t take place.

• Tends to kill microbes by oxidation of cellular components.

• Requires more energy than protein hydrolysis so higher temperatures are required.

• 15 minutes at 160C.

LOW -TEMPERATURE STEAM AND FORMALDEHIDE

• Combination of dry, saturated steam and formaldehyde.

• Sterilization achieved at low temperature (73 C).

• Suitable for heat –sensitive materials and items of equipments with integral plastic component.

FILTRATION

• Great way of quickly sterilizing solutions without heating.

• Works by passing the solution through a filter with a pore diameter that is too small for microbes to pass through.

• Types• Scintered glass funnels.

• Membrane filters.

FILTRATION

• For removal of bacteria, filters with an average pore diameter of 0.2um is normally used.

• Viruses and phage can pass through these filters so filtration is not a good option if these are a concern.

SOLVENTS

• Ethanol

• Peracetic acid (STERIS).

• Isopropanol -- better solvent for fat.

• Work by denaturing proteins through a process that requires water.

• They must be diluted to 60-90% in water to be effective.

• They have no effect on spores.

RADIATION

• UV, x-rays and gamma rays.

• Damaging effects on DNA.

• UV has limited penetration in air so sterilization only occurs in a fairly small area around the lamp.

• Relatively safe.

• Useful for sterilizing small areas.

RADIATION

• X-rays and gamma rays are far more penetrating.• More dangerous.

• Effective for large scale cold sterilization of plastic items e.g. syringes , catheters and I/v cannulas.

Techniques of SterilizaitonSteam (121C for 15 mins) InstrumentsEthylene oxide Heat sensitive instrumentsHot air Sharp delicate instrumentsSteam (73C) and formaldehyde Heat sensitive equipment, PlasticsIrradiation (gamma rays) Industrial packagingPeracetic acid (STERIS) Flexible endoscopes

THANKS