Phenolic disinfectants are used for hard surface decontamination in hospitals and laboratories, eg, floors, beds, and counter or bench tops. They are not recommended for use in nurseries and especially near infants, where their use has been associated with hyperbilirubinemia. Use of hexachlorophene as a skin disinfectant has caused cerebral edema and seizures in premature infants and, occasionally, in adults. It is no longer available in the United States.
The quaternary ammonium compounds (“quats”) are cationic surface-active detergents. The active cation has at least one long water-repellent hydrocarbon chain, which causes the molecules to concentrate as an oriented layer on the surface of solutions and colloidal or suspended particles. The charged nitrogen portion of the cation has high affinity for water and prevents separation out of solution. The bactericidal action of quaternary compounds has been attributed to inactivation of energy-producing enzymes, denaturation of proteins, and disruption of the cell membrane. These agents are fungistatic and sporistatic and also inhibit algae. They are bactericidal for Gram-positive bacteria and moderately active against Gram-negative bacteria. Lipophilic viruses are inactivated. They are not tuberculocidal or sporicidal, and they do not inactivate hydrophilic viruses. Quaternary ammonium compounds bind to the surface of colloidal protein in blood, serum, and milk and to the fibers in cotton, mops, cloths, and paper towels used to apply them, which can cause inactivation of the agent by removing it from solution. They are inactivated by anionic detergents (soaps), by many nonionic detergents, and by calcium, magnesium, ferric, and aluminum ions.
Quaternary compounds are used for sanitation of noncritical surfaces (floors, bench tops, etc). Their low toxicity has led to their use as sanitizers in food production facilities. The CDC recommends that quaternary ammonium compounds such as benzalkonium chloride not be used as antiseptics because several outbreaks of infections have occurred that were due to growth of Pseudomonas and other Gram-negative bacteria in quaternary ammonium antiseptic solutions.
Formaldehyde and glutaraldehyde are used for disinfection or sterilization of instruments such as fiberoptic endoscopes, respiratory therapy equipment, hemodialyzers, and dental instruments that cannot withstand exposure to the high temperatures of steam sterilization. They are not corrosive for metal, plastic, or rubber. These agents have a broad spectrum of activity against microorganisms. They act by alkylation of chemical groups in proteins and nucleic acids. Failures of disinfection or sterilization can occur as a result of dilution below the known effective concentration, the presence of organic material, and the failure of liquid to penetrate into small channels in the instruments. Automatic circulating baths are available that increase penetration of aldehyde solution into the instrument while decreasing exposure of the operator to irritating fumes.
Formaldehyde is available as a 40% weight per volume solution in water (100% formalin). An 8% formaldehyde solution in water has a broad spectrum of activity against bacteria, fungi, and viruses. Sporicidal activity may take as long as 18 hours. Its rapidity of action is increased by solution in 70% isopropanol. Formaldehyde solutions are used for high-level disinfection of hemodialyzers, preparation of vaccines, and preservation and embalming of tissues. The 4% formaldehyde (10% formalin) solutions used for fixation of tissues and embalming may not be mycobactericidal.