Prolongation of the antibacterial potential of disinfected surfaces.

The customary methods of evaluation of chemical disinfectants concern the question of the germicidal performance under specified conditions of these products compared with that of a reference material. As a rule, the fundamental answer is sought to this query: When used in the recommended dilution, will a given disinfectant kill the test-organism wvithin the specified short period of time? From the answer, usually, other information may be developed (partially factual, partially speculative), as, for example, how many times more effective the disinfectant under test is than the reference standard. When translated into practical usage, this information should assure the user of the disinfectant as to the elimination of pathogenic bacteria from a previously contaminated surface, either immediately or shortly after the application of the disinfectant solution. No assurance is furnished ordinarily by such test data as to whether or not this surface will stay "disinfected" for any length of time; in other words, no information is available as to the duration of the antibacterial action, and no suggestion is supplied as to when a reapplication of the disinfectant treatment will be necessary in order to keep the surface free from pathogens. It is somewhat surprising that in the evaluation of disinfectants this problem appears to have been either disregarded or neglected. One might argue that the importance of ascertaining the existence or non-existence of a continuing antibacterial effect is considerablygreater than that of making a comparison with a standard of reference. In any case, the extent to which a disinfectant is capable of yielding a persistent antibacterial potential should certainly be a major factor in its evaluation as a practical adjunct to the control of infectious diseases.