Products containing biocides: perceptions and realities

The mechanisms of action for chemical germicides and antibiotics for inactivating microorganisms are significantly different and methods for determining resistance by microorganisms to these agents are also different. Chemical germicides usually have multiple targets and the mechanisms for inactivation and resistance are not measured in absolute terms but rather in the rapidity with which they reduce levels of microorganisms. The term tolerance is much more suited for germicides than the term resistance. The mechanism of resistance to chemical germicides is often dependent on the concentration of the germicide. At high concentrations multiple cellular and metabolic targets are involved, and at low concentrations fewer cellular targets. In contrast antibiotics usually have a singular cellular or metabolic target and resistance implies the ability of the microorganism to grow in the presence of the antibiotic, and in a clinical sense, to initiate or continue infection in the presence of the antibiotic. When methods used to assess resistance to antibiotics are applied to chemical germicides, inappropriate interpretations can be made regarding the ability of microorganisms to develop resistance to antibiotics as a result of developing resistance to chemical germicides. The use of chemical germicides in health-care institutions and especially the home setting has increased in recent years. Although there may be an overuse of germicides in these settings the consequence is a cost issue and not one that involves the development of antibiotic resistant microorganisms.