Determination of viable Salmonellae from potable and source water through PMA assisted qPCR

•India exhibits high endemicity for salmonellae.•Culture-free PMA assisted qPCR targeting ttr gene quantifies only viable salmonellae.•Assay useful in monitoring potable waters for salmonellae infection.

Resource constrained countries identified as endemic zones for pathogenicity of Salmonella bear an economic burden due to recurring expenditure on medical treatment. qPCR used for Salmonella detection could not discriminate between viable and nonviable cells. Propidium monoazide (PMA) that selectively penetrates nonviable cells to cross-link their DNA, was coupled with ttr gene specific qPCR for quantifying viable salmonellae in source/potable waters collected from a north Indian city. Source water (raw water for urban potable water supply) and urban potable water exhibited viable salmonellae in the range of 2.1×104−2.6×106 and 2–7160 CFU/100 mL, respectively. Potable water at water works exhibited DNA from dead cells but no viable cells were detected. PMA assisted qPCR could specifically detect low numbers of live salmonellae in Source and potable waters. This strategy can be used in surveillance of urban potable water distribution networks to map contamination points for better microbial risk management.

Graphical abstractSchematic representation of PMA™ dye assisted ttr gene-specific molecular beacon based qPCR for detection of viable salmonellae from source water and potable water from urban potable water distribution net work at Lucknow—a major city of northern India. Figure optionsDownload full-size imageDownload as PowerPoint slide