3. Nonionic surfactants: These have little disinfectant activity, and they reduce the 

 effectiveness of other antimicrobial agents. 



4, Amphoteric surfactants: These have bactericidal activity over a wide pH 

 range. They combine the detergent qualities of the anionic surfactants with the 

 bactericidal properties of the cationic surfactants. Amphoteric surfactants have 

 been used as disinfectants in the food industr\- for many years. 



Alcohols — Alcohols have the general formula ( ROH ) in which R is an alk\ 1 or 

 substituted alkyl group. The hydroxyl group (-OH) is the functional group and 

 determines the properties of this family. Ethyl alcohol (CH,CH,OH) is undoubtedly 

 one of the earliest produced and most widely used alcohols. It is sold as rubbing 

 alcohol and used on the skin as a disinfectant. Some water must be present for alcohol 

 to act as a disinfectant, and most rubbing alcohol is sold as 70 percent alcohol and 30 

 percent water. Alcohol is not sporicidal by itself, but it potentiates the sporicidal effect 

 of hypochlorites. 



Heavy Metals — Heavy metals are litde used as veterinary disinfectants. Organic 

 mercury is active against bacteria and mold, although not sporicidal. Silver nitrate 

 has been used on burns. Zinc salts are a mild antiseptic. Copper salts are used as 

 preservatives and as a topical treatment of foot rot in sheep. 



Dyes — Dyes such as trypan red and the flavines were among the earliest attempts at 

 finding drugs that would combat micro-organisms. Acridine dyes such as proflavine 

 and aminacrine are used as topical antiseptics, although they are slow in their action 

 and not sporicidal. Triphenylmethane dyes such as crystal violet, brilliant green, and 

 malachite green are also used as topical antiseptics. Quinones are natural dyes, and 

 some, such as chloranil and dichlone, are powerful agricultural fungicides. 



Gaseous Disinfectants — 



1. Ethylene oxide: This disinfectant is a flammable, water-soluble gas that penetrates 

 paper and cellophane easily. Ethylene oxide is not corrosive and can be used on 

 delicate instruments and electronic equipment. 



2. Propylene oxide: Similar in many ways to ethylene oxide, propylene oxide is less 

 active and penetrates poorly. Thus it cannot be used as effectively when items to be 

 sterilized have been packaged. 



3. 6-Propiolactone: This disinfectant has been used as an inactivating agent in the 

 production of virus vaccines. There is some suggestion that it may be carcinogenic 

 to lixine animals. 



4. Methyl bromide: This gas has been used as a fumigant on soil, grain, and large 

 structures. It is highly toxic and dangerous to use. 



5. Ozone: Ozone has been used as a disinfectant to purify water at the rate of 0.2 to 

 1 mg/L for 3 minutes. 



7-12 



