physical and chemical methods of sterilization pdf

Physical And Chemical Methods Of Sterilization Pdf

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This article is intended to provide a broad overview of common sterilization technologies and the basic elements of sterility assurance, followed by guidelines for selecting a sterilization process. A brief history of microbiology is provided to remind readers how recently it was discovered that sterility is a critical factor in medical procedures. Until the invention of the compound microscope, in which a second lens further magnifies the image from a first lens, individual microorganisms could not be observed.

Methods of sterilization can be broadly classified as:.

Environmental Health & Safety

The purpose of this Guidance Document for Disinfectants and Sterilization Methods is to assist lab personnel in their decisions involving the judicious selection and proper use of specific disinfectants and sterilization methods. Antisepsis : A process involving the destruction or inhibition of mico-organisms in living tissue thereby limiting or preventing the harmful effects of infection.

Antiseptic: Typically an antiseptic is a chemical agent that is applied to living tissue to kill microbes. Note that not all disinfectants are antiseptics because an antiseptic additionally must not be so harsh that it damages living tissue.

Antiseptics are less toxic than disinfectants used on inanimate objects. Due to the lower toxicity, antiseptics can be less active in the destruction of normal and any pathogenic flora present. Autoclave: An autoclave is a high pressure device used to allow the application of moist heat above the normal-atmosphere boiling point of water.

Biocidal: Active substances and preparations which serve to repel, render harmless or destroy chemically or biologically harmful organisms. Decontamination: The killing of organisms or removal of contamination after use, with no quantitative implication, generally referring to procedures for making items safe before disposal.

Disinfectant: A germicide that inactivates virtually all recognized pathogenic microorganisms but not necessarily all microbial forms. They may not be effective against bacterial spores. Disinfection: A procedure of treatment that eliminates many or all pathogenic microorganisms with the exception of bacterial spores. Germicide: An agent that destroys microorganisms, particularly pathogenic microorganisms.

The process of cleaning objects without necessarily going through sterilization. Steam Sterilization: Autoclave, the process of sterilization by the use of heated steam under pressure to kill vegetative microorganisms and directly exposed spores. Special cases may require a variation of the steam temperature and pressure used. Sterilization: The complete elimination or destruction of all forms of life by a chemical or physical means. This is an absolute not a relative term. The information presented in this section will provide a general guideline for selecting a particular disinfectant for use with a given agent.

A brief description of the mode of action of each class of chemical disinfectant is given below. Treatment of inert surfaces and heat labile materials can be accomplished through the use of disinfectants, provided that the following factors are considered:.

The interplay of these factors will determine the degree of success in accomplishing either disinfection or sterilization. Do not attempt to use a chemical disinfectant for a purpose it was not designed for. However, multiple investigators have demonstrated the effectiveness of these disinfectants against vegetative bacteria e.

Federal law requires all applicable label instructions on EPA-registered products to be followed e. Formaldehyde — and its polymerized solid paraformaldehyde have broad-spectrum biocidal activity and are both effective for surface and space decontamination.

Its biocidal action is through alkylation of carboxyl, hydroxyl and sulfhydryl groups on proteins and the ring nitrogen atoms of purine bases. Formaldehyde is presently considered to be a carcinogen or a cancer-suspect agent according to several regulatory agencies.

The OSHA 8-hour time-weighted exposure limit is 0. Paraformaldehyde — is a solid polymer of formaldehyde. This process is used for the decontamination of large spaced and laminar-flow biological safety cabinets when maintenance work or filter changes require access to the sealed portion of the cabinet.

A neutralization step, heating ammonium carbonate, is required prior to ventilation of the space. Formaldehyde gas can react violently or explosively 7. Glutaraldehyde — is a colorless liquid and has the sharp, pungent odor typical of all aldehydes, with an odor threshold of 0. It is capable of sterilizing equipment, though to effect sterilization often requires many hours of exposure. Two percent solutions of glutaraldehyde exhibit very good activity against vegetative bacteria, spores and viruses.

It is ten times more effective than formaldehyde and less toxic. However, it must be limited and controlled because of its toxic properties and hazards. It is important to avoid skin contact with glutaraldehyde as it has been documented to cause skin sensitization. Glutaraldehyde is also an inhalation hazard. Cidex, a commercially prepared glutaraldehyde disinfectant is used routinely for cold surface sterilization of clinical instruments. Chlorine compounds are good disinfectants on clean surfaces, but are quickly inactivated by organic matter and thus reducing the biocidal activity.

They have a broad spectrum of antimicrobial activity and are inexpensive and fast acting. Hypochlorites, the most widely used of the chlorine disinfectants, are available in liquid e. Household bleach has an available chlorine content of 5. Because of its oxidizing power, it loses potency quickly and should be made fresh and used within the same day it is prepared.

There are two potential occupational exposure hazards when using hypochlorite solutions. The first is the production of the carcinogen bis-chloromethyl ether when hypochlorite solutions come in contact with formaldehyde.

The second is the rapid production of chlorine gas when hypochlorite solutions are mixed with an acid. Care must also be exercised in using chlorine — based disinfectants which can corrode or damage metal, rubber, and other susceptible surfaces.

Bleached articles should never be autoclaved without reducing the bleach with sodium thiosulfate or sodium bisulfate. Chloramine T which is prepared from sodium hypochlorite and p-toluenesulfonamide is a more stable, odorless, less corrosive form of chlorine but has decreased biocidal activity in comparison to bleach. Iodophors are used both as antiseptics and disinfectants. An iodophor is a combination of iodine and a solubilizing agent or carrier; the resulting complex provides a sustained-release reservoir of iodine and releases small amounts of free iodine in aqueous solution.

Antiseptic iodophors are not suitable for use as hard-surface disinfectants because they contain significantly less free iodine than do those formulated as disinfectants. Both bleach and iodophors should be made up in cold water in order to prevent breakdown of the disinfectant. Quaternary ammonium compounds are generally odorless, colorless, nonirritating, and deodorizing. They also have some detergent action, and they are good disinfectants.

However, some quaternary ammonium compounds activity is reduced in the presence of some soaps or soap residues, detergents, acids and heavy organic matter loads. They are generally ineffective against viruses, spores and Mycobacterium tuberculosis. Basically these compounds are not suitable for any type of terminal disinfection. The mode of action of these compounds is through inactivation of energy producing enzymes, denaturation of essential cell proteins, and disruption of the cell membrane.

Many of these compounds are better used in water baths, incubators, and other applications where halide or phenolic residues are not desired. Phenolics are phenol carbolic acid derivatives. These biocides act through membrane damage and are effective against enveloped viruses, rickettsiae, fungi and vegetative bacteria. They also retain more activity in the presence of organic material than other disinfectants.

Cresols, hexachlorophene, alkyl- and chloro derivatives and diphenyls are more active than phenol itself. Strong mineral acids and alkalis have disinfectant properties proportional to the extent of their dissociation in solution. Some hydroxides are more effective than would be predicted from their values. In general acids are better disinfectants than alkalis. Weak organic acids are more potent than inorganic acids despite low dissociation rates in solution. Soluble salts of mercury, silver lactate, mercuric chloride and mercurous chloride are efficient bactericidal agents.

Silver nitrate and mercuric chloride are commonly used as aqueous solutions. Organic matter can reverse the disinfectant properties of mercurials. Specifically, disposal of elemental mercury and salts of mercury are very costly.

Alcohols work through the disruption of cellular membranes, solubilization of lipids, and denaturation of proteins by acting directly on S-H functional groups.

Ethyl and isopropyl alcohols are the two most widely used alcohols for their biocidal activity. These alcohols are effective against lipid-containing viruses and a broad spectrum of bacterial species, but ineffective against spore-forming bacteria. They evaporate rapidly, which makes extended contact times difficult to achieve unless the items are immersed.

Absolute alcohol is also not very effective. They are used to clean instruments and wipe down interior of Biological Safety Cabinets and bottles, etc. Alcohols are generally regarded as being non-corrosive. In addition, this autoclave must be checked by an authorized service provider at least every 6 months preferably every days to assure proper function, i. Care must be taken to ensure that the steam can circulate around articles in order to provide even heat distribution.

The success of the sterilization is very time-dependent in liquid media, with large volumes requiring longer periods of time to reach the effective temperature within the media itself. Additionally, there should be no void spaces in the load that could insulate against the steam — this condition could prevent the transference of heat to the vessels resulting in no sterilization of the contents.

In dry loads small amounts of water should be included inside the autoclave bag to ensure sufficient moisture content within the load to allow for heat transference and distribution. Autoclave tape can be used for routine runs where glassware or sterile media are prepared before use. Hence, chemical indicators can give a quick visual reference for heat penetration inside the autoclave. Chemical indicators should be positioned near the center of each load, and toward the bottom front of the autoclave.

Caution: Most chemical indicators can only be used to verify that your autoclave has reached normal operating temperatures for decontamination; they have no time factor.

Chemical indicators alone are not designed to prove that organisms are actually killed during a decontamination cycle. Tape indicators are adhesive backed paper tape with heat sensitive, chemical indicator markings. These markings only appear when the tape has been exposed for a few minutes to normal autoclave decontamination temperatures.

Caution: Tape indicators can only be used to verify that your autoclave has reached normal operating temperatures for decontamination; they have no time factor. Tape indicators alone are not designed to verify that organisms are actually killed during a decontamination cycle. Biological indicators are designed to demonstrate that an autoclave is capable of killing microorganisms. This test must be performed at least every 90 days.

Always post the results of the test on or near the autoclave — Date Performed; Test Result; Name of Person doing test.


The next two labs deal with the inhibition, destruction, and removal of microorganisms. Control of microorganisms is essential in order to prevent the transmission of diseases and infection, stop decomposition and spoilage, and prevent unwanted microbial contamination. Microorganisms are controlled by means of physical agents and chemical agents. Physical agents include such methods of control as high or low temperature, desiccation, osmotic pressure, radiation, and filtration. Control by chemical agents refers to the use of disinfectants, antiseptics, antibiotics, and chemotherapeutic antimicrobial chemicals. Basic terms used in discussing the control of microorganisms include:.

Lab 18: Use of Physical Agents to Control of Microorganisms

A method employed to minimize the growth of organisms and transmission of disease from one individual to another. In the environment the use of disinfection techniques decreases the growth of bacteria on surfaces, which leads to the decrease in transmission of organisms amongst the population. These techniques are commonly used today in medical care and food industry. Figure 1: on the right illustrating all the techniques used.

For thousands of years, humans have used various physical methods of microbial control for food preservation. Common control methods include the application of high temperatures, radiation, filtration, and desiccation drying , among others. Many of these methods nonspecifically kill cells by disrupting membranes, changing membrane permeability, or damaging proteins and nucleic acids by denaturation, degradation, or chemical modification.

PhD in Nursing. Correspondence addressed to. The objective of this descriptive study was to identify the physical, chemical and biological controls of the sterilization process by saturated steam in Pasteur autoclaves at Material and Sterilization Centers MSC. A total 44 municipalities participated. The analysis was performed using SPSS software.



Slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. If you continue browsing the site, you agree to the use of cookies on this website. See our User Agreement and Privacy Policy. See our Privacy Policy and User Agreement for details. Published on Dec 2, Sterilization physical methods.

The purpose of this Guidance Document for Disinfectants and Sterilization Methods is to assist lab personnel in their decisions involving the judicious selection and proper use of specific disinfectants and sterilization methods. Antisepsis : A process involving the destruction or inhibition of mico-organisms in living tissue thereby limiting or preventing the harmful effects of infection. Antiseptic: Typically an antiseptic is a chemical agent that is applied to living tissue to kill microbes.

forms of microbial life and is carried out in health-care facilities by physical or. chemical methods. Sterilisation and Disinfection. MICROBIOLOGY. MODULE.

Sterilization- physical and chemical methods

Last Updated on January 3, by Sagar Aryal. Microorganisms play an important role in causing infection and contamination. Therefore, Sterilization is an important technique in microbiology which helps to remove or destroy microorganisms from materials or surfaces. It is the process by which an article, surface or medium is made free of all microorganisms either in vegetative or spore form. It refers to the destruction of all pathogens or organisms which can cause infection but not necessarily spores.

Sterilization, which is any process, physical or chemical, that destroys all forms of life, is used especially to destroy microorganisms, spores, and viruses. Precisely defined, sterilization is the complete destruction of all microorganisms by a suitable chemical agent or by heat, either wet steam…. More than 50 percent of the ionizing radiation to which humans are exposed comes from natural radon gas, which is an end product of the radioactive decay chain…. Sterilization of disposable medical supplies, such as syringes, blood transfusion kits, and hospital gowns, is usually done with gamma rays.

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