Detection of Viable Escherichia coli in Environmental Water Using a Combined Propidium Monoazide Staining-Real-time PCR

Escherichia coli, as a principal fecal indicator bacterium, is used to monitor water quality world-wide. Real-time PCR (qPCR) is a promising way to achieve a rapid and sensitive detection of E. coli in water samples. The ability to detect only viable E. coli cells specifically provides a more accurate reflection of water quality and safety. The objective of this study was to test a new self-designed primer set targeting the ycjM gene of E. coli in a propidium monoazide (PMA)-qPCR assay, and to investigate its specificity and efficiency in detecting only viable E. coli in environmental water. Specificity of the ycjM primer set was checked using nineteen different E. coli strains, including E. coli ATCC 25922, E. coli K12, E. coli O157 strains and strains from environmental sources, as well as Shigella. dysenteriae, S. flexneri and S. sonnei. It showed that ycjM primers could detect most of the E. coli strains but did not amplify any DNA from Shigella strains.