chemical procedures to destroy all forms of microbial life, including highly resistant bacterial endospores. Sterilization is frequently accomplished using high-pressure steam autoclaving, ethylene oxide gas, or prolonged exposure to dry heat. Disinfection is the elimination of all vegetative microorganisms and pathogenic viruses, but not bacterial or fungal spores, from an inanimate object. As such, disinfection processes lack the margin of safety achieved through sterilization procedures. Furthermore, the effectiveness of a disinfection procedure is influenced significantly by a number of factors, including the nature and number of contaminating microorganisms, the type and condition of the materials to be disinfected, and the amount of organic matter (such as blood) present (Klein and Deforest, 1965a; Rhame, 1986; Rutala and Weber, 1987; Rutala, 1987; Van Houton and Hayre, 1991).

A germicide is an agent that destroys microorganisms, especially pathogens, on either living or inanimate objects. Disinfectants can be categorized into high-, medium-, and low-level agents based on their potency of germicidal action. Disinfectants that are widely used at present include alcohols, hypochlorites (such as bleach) and other chlorine-containing compounds, formaldehyde, glutaraldehyde, hydrogen peroxide, iodophors, phenolics, and quaternary ammonium compounds. The level of contamination with organic matter of objects to be disinfected is referred to as the bioburden, and it is of particular importance in the disinfection of surfaces contaminated with blood that harbors infectious pathogens. Contact time is defined as the length of time that a contaminated object or surface is exposed to a disinfectant. Cleaning is the removal of foreign (especially organic) material. Decontamination is the removal of pathogenic microorganisms from objects so they are safe to handle.

The Role of Cleaning in Disinfection

Thorough cleaning must always precede chemical disinfection of any equipment (Klein and Deforest, 1965a; Rhame, 1986; Rutala and Weber, 1987; Rutala, 1987; Van Houton and Hayre, 1991). The mechanical action of cleaning can itself remove a large proportion of the microorganisms present. Cleaning also removes organic material that can inactivate or diminish the potency of the germicide used. The presence of blood on or in equipment being processed for reuse, including needles and syringes, can contribute to the failure of a given disinfection or sterilization procedure in three ways. First, organic material may contain large and/or diverse microbial populations. Second, it may trap microorganisms and prevent effective penetration of chemical germicides. Third, it may directly and rapidly inactivate certain germicidal chemicals, including bleach and other chlorine-containing solutions, iodine-based disinfectants, and quaternary ammonium-based



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