DISINFECTANTS AND STERLANTS Definition Disinfectant is a germicidal, chemical substance that kills microorganisms on inanimate objects, such as instruments and other equipment, that cannot be exposed to heat. Disinfectants differ in their spectrum of activity. They do not kill the tubercle bacillus or spores. Antiseptic is a chemical agent that either kills pathogenic microorganisms or inhibits their growth as long as there is contact between agent and microbe. By custom as well as federal law, the term "antiseptic" is reserved for agents applied to the body. Sterilization is the process of killing all microorganisms including all bacteria, fungi, viruses, and spores with the use of either chemical or physical agents. Agents The following agents are commonly used as disinfectants, and antiseptics, and sterilants. Glutaraldehyde: 2% glutaraldehyde solution are used for cold sterilization. They are commercially available as Cidex (Surgikos-Johnson & Johnson) and Sporicidin (Ash-Dentsply). These agents are diluted with an activator prior to use and have limited shelf lives after dilution (14 days for Cidex; 30 days for Sporicidin). they can be used for disinfection or sterilization depending upon the time allowed for instrument contact. Cidex and Sporicidin require 10 hours of contact time for sterilization. Instruments may be soaked for 10 minutes in Cidex solution, to remove vegetative bacteria, when performing surgical procedures on multiple animals as long as they are sterilized throughly before the first procedure in the sequence. Glutaraldehyde is toxic to skin and mucous membranes. It must be rinsed from instruments and other items with sterile water before use. It is the "cold" sterilant of choice for lensed instruments. Chlorine Compounds: Household Bleach (5% sodium hypochlorite) is effective against all classes of microorganisms but is inactivated by organic debris. It can be used as a disinfectant on previously cleaned surfaces at a dilution of 1:20. Full strength or a 1:5 dilution is recommended against hepatitis B virus, HIV or on surfaces soiled by potentially contaminated fluids. Some authors claim that the tubercle bacillus and other similar organisms are resistant to hypochlorite. it must be made fresh; solutions that are allowed to sit may deteriorate. Bleach will damage fabric and is an irritant to mucous membranes. Chlorine dioxide (Clidox or Alcide), is available as a binary system, consisting of a base and an activator, which require mixing. Once prepared the usable life of the solution is 14 days. Chlorine dioxide is effective against all classes of microorganisms including bacterial spores. Three minutes of contact time is necessary for efficacy. Alcohols: Alcohols destroy bacteria via the coagulation of protein. They have poor activity against bacterial and fungal spores, evaporate rapidly if kept in open containers, form flammable mixtures with air, are inactivated by organic matter, and dissolved lens cement mountings. In spite of these shortcomings, they are rapidly bacteriocidal and are useful antiseptics. Isopropyl alcohol is typically used as a 70% solution; ethyl alcohol is used between 75 and 90%. Ethyl alcohol has abuse potential and must be kept in locked cabinets. When used as antiseptics, they are disinfectants as long as they remain in solution. As such they may be used for emergency disinfection of instruments by immersion for 20 minutes. Povidone-Iodine: Free iodine is complexed to the polymer povidone to produce a non-toxic antiseptic. Povidone-iodine is effective against all classes of microorganisms. It is most commonly used as a surgical scrub (Betadine Scrub, Purdue-Frederick) at 7.5%. It is also available as a 10% solution (Betadine Solution); the solution is used undiluted to paint the skin after an appropriate surgical scrub. Chlorhexidine acetate: Chlorhexidine acetate is commercially available as both a 2% solution and 2% surgical scrub (Nolvasan Solution; Nolvasan Surgical Scrub, Aveco/Fort Dodge). The scrub is used undiluted as a antiseptic. The solutions used as a disinfectant by diluting 3 ounces to a gallon of water. Nolvasan solution is not effective against gram + cocci or pseudomonas aeruginosa on inanimate objects. Chlorhxidine is neutralized by alcohols, therefore the two agents should not be used in combination. Quaternary ammonium compounds (Benzalkonium chloride): The two products included in this group of agents are Roccal D (Winthrop) and Zephiran (Winthrop). Roccal D is used to decontaminate surface (i.e it is not used on instruments). A 1:200 dilution with water is recommended by the manufacturer. It is effective against a variety of viruses, gram + and gram - bacteria. Zephiran has been largely supplanted as an antiseptic by Betadine. When Zephiran is used, it is used as a "tincture" (i.e with alcohol at a dilution of 1:750). Zephiran may be used to disinfect instruments between animals (20 minute soak) when surgical procedures are performed on multiple animals during a session. These agents have no effect against the tubercle bacillus and are inactivated soaps. Ethylene oxide: Ethylene oxide is a cyclic ether with bacteriocidal, sporicidal and fungicidal properties. It is used in its gaseous state and is marketed in ampules under the trade name Anprolene (Andersen Products). Partial pressure of the agent is important for microbiocidal effect, Ethylene oxide can be used to sterilize heat sensitive plastics and lensed instruments. Items must be exposed to ethylene oxide for 12 hours and then aerated. Aeration times range from several hours to weeks depending upon whether passive or mechanical aeration is used. Aeration is required because ethylene oxide is a skin and mucous membrane irritant. Ethylene oxide sterilization and aeration should be done under a fume hood; gloves should be worn when breaking the ethylene oxide ampule or when handling ethylene oxide sterilized items prior to aeration. Alkylation of nucleic acids is considered the mechanism of action. Objects sterilized by radiation should not be resterilized with ethylene oxide (toxins are produced that are difficult to elute). =========================================================================== Click here to Appendix I