Definitions - Chemical Disinfectants, Antiseptics And Preservatives

DEFINITIONS

A)  Disinfectant And Disinfection

Disinfection is the process of removing microorganisms, including pathogens, from the surfaces of inanimate objects. The British Standards Institution (BSI) further defines disinfection as not necessarily killing all microorganisms but reducing them to a level acceptable for a defined purpose, for example, a level that is harmful neither to health nor to the quality of perishable goods. Chemical disinfectants are capable of different levels of action (Table 19.1). The term high-level disinfection indicates destruction of all microorganisms but not necessarily bacterial spores; intermediate-level disinfection indicates destruction of all vegetative bacteria including Mycobacterium tuberculosis but may exclude some resistant viruses and fungi and implies little or no sporicidal activity; low-level disinfection can destroy most vegetative bacteria, fungi and viruses, but this will not include spores and some of the more resistant microorganisms. Some high-level disinfectants have good sporicidal activity and are described as liquid chemical sterilants or chemosterilants to indicate that they can effect a complete kill of all microorganisms, as in sterilization. In defining each of these disinfection levels the activity and outcome is determined by correct use of the disinfectant product in regard to concentration, time of contact and prevailing environmental conditions as described in this article series.

B)   Antiseptic And Antisepsis

Antisepsis is defined as destruction or inhibition of microorganisms on living tissues having the effect of limiting or preventing the harmful results of infection. It is not a synonym for disinfection (BSI). The chemicals used are applied to skin and mucous membranes, so as well as having adequate antimicrobial activity they must not be toxic or irritating for these tissues. Antiseptics are mostly used to reduce the microbial population on the skin before surgery or on the hands to help prevent spread of infection by this route. Antiseptics are sometimes formulated as products containing significantly lower concentrations of agents used for disinfection.

C)   Preservative And Preservation

Preservatives are included in pharmaceutical and many other types of formulations, both to prevent microbial spoilage of the product and to minimize the risk to the consumer of acquiring an infection when the preparation is administered. Preservatives must be able to limit proliferation of microorganisms that may be introduced unavoidably into non-sterile products such as oral and topical medications during their manufacture and use. In sterile products, where multiuse preparations remain available, preservatives should kill any microbial contaminants introduced inadvertently during use. It is essential that a preservative is not toxic in relation to the intended route of administration of the preserved preparation. Preservatives tend to be employed at very low concentrations and consequently levels of antimicrobial action also tend to be of a lower order than for disinfect-ants or antiseptics. This is illustrated by the European Pharmacopoeia requirements for preservative efficacy where a degree of bactericidal activity is necessary, although this should be obtained within a few hours or over several days of microbial challenge depending on the type of product to be preserved.