Disinfection of surfaces and equipment.

C hemical disinfection of surfaces and instruments is an important aspect of infection control as routinely practised in dental units and elsewhere. The timing and method of chemical disinfection, the factors affecting the efficacy of germicides and the hazards posed by their use are important considerations in selecting disinfectants. The terminology used for such chemicals is often confusing, and many of the common synonyms (such as biocide, microbiocide, germicide and disinfectant) imply a broad spectrum of efficacy against a range of microbial pathogens. However, a given product may actually carry claims for activity against only one class of microorganisms, usually vegetative bacteria. Therefore, the user is urged to closely examine a product's label claims before purchase to assess its potential for surface disinfection or decontamination. The main reason for practising disinfection is to interrupt transmission of pathogens from an infected individual to a susceptible host. Disinfection of air is impractical, potentially hazardous and usually ineffective in preventing transmission of airborne microorganisms, so disinfection is usually confined to the use of liquid chemical germicides on environmental surfaces and equipment. When a pathogen is shed into the environment it contaminates surfaces either directly or through settled aerosols. Depending on the nature of the pathogen and its suspending medium, as well as environmental factors such as temperature and relative humidity, organisms can survive for periods from a few minutes to several weeks or even months. The initial drying period affects pathogen viability to varying degrees, but fractional amounts of most pathogens can be detected up to several hours on contaminated surfaces. During that time, contact with the contaminated item may result in direct inoculation of a susceptible host or, more likely, contamination of another vehicle, such as the hands, by means of which indirect inoculation occurs. Disinfectants can be effective in limiting the survival of pathogens and their transfer to susceptible hosts or secondary vehicles. Heat sterilization, when possible, is always preferred to chemical disinfection. However, high-level chemical disinfec-tion of instruments after each use may be necessary in some situations. The determination of the need to disinfect environmental surfaces is usually a matter of assessing the relative risks to patients and staff from exposure to frequently contacted surfaces that may be at risk of contamination, either directly or from settled aerosols. Efficient disinfection depends on 3 principles, which are equally important in achieving a successful result. The product is important because a poor …