AWWA WQTC71352

This paper presents preliminary results of method development studies of a culture and qPCR method where unstressed and stressed bacteria were inoculated into different matrices at different densities. This type of method offers both a demonstration of viability through culture, and the detection specificity and sensitivity of qPCR. The study sought a culture method that is able to recover stressed bacteria, and has some selectivity for coliform bacteria. The criteria for qPCR detection was that it must be able to detect the target bacteria in the presence of a natural bacterial background, and be able to detect a wide enough range of target bacterial concentrations to demonstrate that a change in density had occurred during incubation. The approach for demonstrating viability of target bacteria was to conduct an initial (qPCR) analysis at the time that incubation was initiated and a final qPCR analysis after a period of incubation. The difference in qPCR signal of samples taken before and after incubation was seen as evidence of growth. Wherever possible, the study used commercially available products to minimize method development and preparation time. Additionally, the paper presents the results of the use of this method with natural surface water samples that were taken from streams suspected of having E. coli O157:H7 contamination. Includes 6 references.