Sterilization

Sterilization:- 

Definition

It is a process of making something free from bacteria or other living organism either in vegetative or spores. The removal of all microorganism from an object or surface.

Disinfection

The process of cleaning something. Especially with a chemical in order to destroy or kill bacteria, but not necessarily spores.

·           Physical method

·           Chemical method Radiation

·           Filtration

·           Mechanical

Methods of disinfection and Sterilization:

. . . Mechanical Method

Scrubbing: Hand washing is one of the important procedures of a nurse in order to control and prevent self-infection as well as cross infection.

Filtration: Filtration is the passage of a liquid fluid or gases through a filter with pores small enough retain microbes – vaccine, toxins, enzymes.

e.g. - HEPA filter, Membranes filters (nitrocellulose)

Sedimentation: - It is used in the purification of water by this method the suspending material together with bacteria settles down in the bottom of liquid.

. . . hysical methods

Sunlight: Sunlight contains UV rays which cause thymine dimer in the DNA of bacterial cells. These UV says stops the replication of DNA in bacterial cells. These rays has more antimicrobial action e.g. Blanket, Pillows.

Dry heat: -

Direct flaming: -

·           Very effective method of sterilization.

·           Burning contaminants to ashes.

·           This is used to sterilizing inoculation loops and sterilizing needles and instruments killing organisms.

Incineration: All hospital wastages like dressing, garbage, contaminated materials are completely bunt by incineration. It is very effective to kill all organism.

Hot air oven: This instrument is used to sterilize glassware, syringes, needles, culture tubes and enhance the growth of micro organism in culture media The vegetative forms of bacteria can be killed by this at 160°C for1 hour.

Moist heat Sterilization

Boiling: At a temperature of 100°C boiling for 3 to 5 minutes kill microorganisms except spore bearing organisms.

·           This method is suitable for enamel, metal, glass, rubber wares.

Points to remember

·           The article must be cleaned by scrubbing to remove the organic matter.

·           Great care should be taken for glass articles and they should be wrapped with cloth and put in cold water and then brought to boil.

·           The organic matter which will coagulate around the organism and protect them.

·           Testing material to check effectiveness of sterilization.

Autoclaving (Above 100°C temperature)

Spore bearing organism Ex. Clostridium tetani are killed by steam under pressure.

Autoclave is an apparatus used for sterilization of articles by steam under pressure.

·           It is a metal chamber with an outer jacket and a lid, which can be firmly clamped. Steam is generated by heating water in a boiler or in the outer jacket.

In this the steam is allowed to circulate in a closed container and it is compressed and there by raises the temperature above the boiling point of water (at 121°C for 15 to 30 minute). Then the heat is turned off. The steam is evacuated.

Ses

The materials sterilized by autoclaving method are dressing, gloves, lines, syringes, certain instruments and culture Medias.

points to remember

·           All articles should be clean and dry before packing. Any organic matter such as blood or pus prevents penetration of steam.

·           The holes in drum must be open when placing into the auto clave, and closed immediately on taking them out.

·           Rubber gloves cannot stand high temperature and long sterilizing. Autoclave those separately at 15 lbs. pressure for 15 minutes.

·           To auto clave bottles of fluids loosen the screw caps, evacuate the steam slowly.

Pasteurization: (Temperature at 62.8°C)

In pasteurization a high temperature is used for a short time (72°C for 15 minutes) to destroy pathogens without altering the flavor of the food. This process is used to kill all the pathogenic organisms in milk, cream, and certain alcoholic beverages.

Chemical Methods

Certain chemicals are used in disinfection of articles like thermometer and also the disinfection of floor and de-contamination of infected linen.

Chemical Substance which are commonly used:

1.        Dettol: This is widely used chemical for Sterilization of instruments, thermometer etc. 5 to 50% of solution is used for drawings and wound irrigation.

2.        Savlon: 1:30 solution is used to destroy or kill vegetative bacteria.

3.        Chloride of lime (bleaching powder): This is used for disinfection of drinking water, stools, urine, sputum. As it decomposes quickly when exposed to air. Solutions must be prepared fresh for each use.

4.        Formalin: - A 40% solution is used to disinfect faces, urine and sputum. It is not used for the skin and tissue, as it is an irritant.

5.        Tincture of Iodine: - 1-2% iodine is used for cleaning skin and treating injuries to the skin.

6.        Hydrogen peroxide: 1-5% of solution is used in cleaning wounds and to remove pus from infected ears. Hydrogen peroxide is also used to clean the mouth. It is an oxidizing agent.

7.        Potassium Permanganate: - It is an oxidizing agent used for cleaning the mouth with 1:1000 strength. It is also used for irrigation of wounds.

8.        Carbolic acid (Phenol): - It is a good designating for feces, pus, blood and sputum. It is a skin irritant and a poison. Dissolves early in hot water. For thermometer 1:20 solution for a duration of 10 minutes.

9.        Lysol: This is a phenol preparation mixed with soap. It is less poisonous than a carbolic acid but has a greater bactericidal action. 2% of solution for 6-8 hours is wed for disengaging livens.

10.   Ethyl Alcohol: 70% is effective for skin disinfection. Certain gases like formaldehyde and glutaral-dehyde are used in disinfection of rooms.

Radiation

The effects of radiation depend on its wave length, intensity, duration.

Ionizing radiation

·           Gamma  rays  and  x-rays  are  both types of high energy electron (high frequency ) electromagnetic radiation

·           These rays can cause destruction of the DNA in microbes.

·           The principal effect of ionizing radiation is the ionization of water, which forms highly reactive hydroxyl radicals.

on Ionizing   radiation rays

UV light damages the DNA of the exposed cells. It causes bonds to form between adjacent thymine dimers in DNA chain and inhibit replication.

USES

The radiations are used for sterilizing pharmaceutical and medical dental carries. (cold sterilization)

·           Practical application is the UV lamp (germicidal property) in the microbiological laboratories.

Fumigation (or) Gas Sterilization

Fumigation is a process of gaseous sterilization which is used for killing of microorganisms and prevention of microbial growth in air, surface of wall or floor.

·           It is generally used in the pharmaceutical, operation theatres. Hospitals, and offices.

·           For effective fumigation process is done according to the density. Humidity 60% and temperature never below 18° C in opened area around at a time of 1 hour to o16 hours it may be differ the gas kill all the spores, vegetative cells etc.,

Gaseous agents

·           Formaldehyde

·           Ethylene oxide

·           Glutaraldehyde

·           Propiolactone

Disadvantage: These gas may cause irritant to the eyes, and mucous membranes and un wanted odors.

Low temperature:

Cold has the effect of decreasing or completely stopping the growth of bacteria constant freezing will destroy and inhibit the growth of bacteria.

In freeze condition the organisms growth may be delayed or inhibited. The organisms can be destroyed often is freeze conditions.

Principles to be observed:

1.        All articles contaminated with blood, feces, pus, sputum or other substances must be rinsed with cold water to prevent coagulation of protein material.

2.        Use soap and water for cleaning the instruments and use a brush whenever necessary.

3.        Allow sufficient time for articles to be disinfected or sterilized by physical or chemical agents.

4.        It is importance to select the right disinfectant, the right strength and the right time.

5.        Use the right procedure to render instruments and other articles safe for further use in order to prevent the spread of infection.