Ethidium and propidium monoazide: comparison of potential toxicity on Vibrio spp. viability.

Vibrio spp., ubiquitous in the aquatic ecosystem, are bacteria of interest because of their involvement in human health, causing gastroenteritis after ingestion of seafood, as well as their role in vibriosis leading to severe losses in aquaculture production. Their ability to enter a viable but non-culturable (VBNC) state under stressful environmental conditions may lead to underestimation of the Vibrio population by traditional microbiological enumeration methods. As a result, using molecular methods in combination with EMA or PMA allows the detection of viable (VBNC and culturable viable) cells. In this study, the impact of the EMA and PMA was tested at different concentrations on the viability of several Vibrio species. We compared the toxicity of these two DNA-binding dyes to determine the best pretreatment to use with qPCR to discriminate between viable and dead Vibrio cells. Our results showed that EMA displayed lethal effects for each strain of V. cholerae and V. vulnificus tested. In contrast, the concentrations of PMA tested had no toxic effect on the viability of Vibrio cells studied. These results may help to achieve optimal PMA-qPCR methods to detect viable Vibrio spp. cells in food and environmental samples.