Laser scanning cytometry to detect viable but non-culturable C. jejuni in drinking water

Laser scanning cytometry has been investigated as a tool to detect viable but non-culturable C. jejuni in drinking water. After suspending the cells in sterile drinking water, a sample was taken every seven days, the (see text) were retained on a polyester membrane filter and labelled using a fluorescein derivative as a substrate for intracellular esterases. The number of green fluorescent bacteria was automatically counted by an Ar laser scanning device in three minutes. In parallel, the number of culturable cells was determined on a non-selective medium. The number of culturable cells decreased to below the detection limit for cultivation in less then 50 days. At the contrary, fluorescent bacteria remained at the initial level during the 71 days of incubation. The discrepancy between the two results can be assigned to the presence of VBNC C. jejuni cells. Therefore laser scanning cytometry can be used as a fast and sensitive tool to detect viable but non-culturable C. jejuni in drinking water.