Effect of Aquatic Exposure and Disinfection on the Virulence of Enteric Pathogens

摘要

Studies were conducted to examine the persistence of enteric pathogens and their virulence-related properties with exposure to aquatic stress and disinfection. The initial effort was devoted to the adaptation of image analysis instrumentation in the rapid assessment of bacterial viability and injury in water using the direct viable count (DVC) technique. The analytical approach proved to be very useful in generating sufficient objective data for rigorous statistical analysis in a short time. Using the approach it was found that a range of enteric pathogenic and indicator bacteria each have different optima for both nalidixic acid and nutrients. The observation indicates that the common practice of using one level of the ingredients can lead to artificial results. A series of experiments also examined the survival of enteric pathogens in water and the response to suboptimal disinfection. The results revealed that the pathogens have extended persistence in temperate, agricultural surface water and that experiments using enclosed vessels, microcosms, can lead to misleading results concerning both survival and extended pathogenic potential. Exposure to low concentrations of chlorine also led to injury and reduced virulence-related properties.