Should test methods for disinfectants use vertebrate viruses dried on carriers to advance virucidal claims?

izontal surfaces in the rooms of patients with C. difficile infection. It would be obtuse to assume that in vitro experiments precisely simulate in vivo conditions. Similarly, relying solely on an antimicrobial agent's minimum inhibitory concentration to predict its clinical efficacy against a particular infecting pathogen is ill-advised. Thus, it is standard practice to employ in vitro models of infection to simulate, among other factors, waning concentrations of an antimicrobial agent after each dose is administered. The impact of cleaning and disinfecting agents should be viewed no differently. Initial working strength concentrations applied to surfaces do, in fact, wane over time. Subsequently, in germicides and/or cleaning agents, the residual active components are exposed to organic material (eg, feces containing C. difficile in both vegetative and spore forms). If working strength concentrations were universally delivered after their initial application, it would be surprising if the environment was ever implicated in the spread of infection. We caution against assuming that use of a germicide or a cleaning agent guarantees effective environmental decontamination; it does not. Thus, it has been shown that as the level of environmental contamination with C. difficile increases, so does the magnitude of healthcare worker hand contamination. In our article, we acknowledged that the clinical significance of results showing an increased rate of sporulation associated with use of some cleaning agents and/or germicides is unknown. However, as pointed out by Holtschlag, the US Enironmental Protection Agency does not currently recognize a test method for inactivation of C. difficile spores. It is logical, therefore, to use different test methodologies and to base any conclusions concerning the potential efficacy of agents against C. difficile on all of the results obtained. This is what we did. It would be unwise to pick and choose which results appear more favorable, particularly, as in Holtschlag's case, if there is a potential conflict of interest. Hence, we concluded our report by stating that "the combined body of evidence suggests that dichloroisocyanurate (ie, chlorine-release) germicides currently represent the optimum choice for the removal of C. difficile from healthcare environments." We went on to say that our results "suggest that compounds that do not kill C. difficile spores at working concentrations, such as general-purpose detergents and hydrogen peroxide, may promote the persistence and accumulation of spores in healthcare environments." We stand by these comments.