Dynamics of V ibrio cholerae abundance in Austrian saline lakes, assessed with quantitative solid‐phase cytometry

In order to elucidate the main predictors of V ibrio cholerae dynamics and to estimate the risk of V ibrio cholera‐related diseases, a recently developed direct detection approach based on fluorescence in situ hybridization and solid‐phase cytometry (CARD‐FISH/SPC) was applied in comparison to cultivation for water samples from the lake Neusiedler See, Austria and three shallow alkaline lakes over a period of 20 months. V ibrio cholerae attached to crustacean zooplankton was quantified via FISH and epifluorescence microscopy. Concentrations obtained by CARD‐FISH/SPC were significantly higher than those obtained by culture in 2011, but were mostly of similar magnitude in 2012. Maximum cell numbers were 1.26 × 10(6) V . cholerae per L in Neusiedler See and 7.59 × 10(7) V . cholerae per L in the shallow alkaline lakes. Only on a few occasions during summer was the crustacean zooplankton the preferred habitat for V . cholerae. In winter, V . cholerae was not culturable but could be quantified at all sites with CARD‐FISH/SPC. Beside temperature, suspended solids, zooplankton and ammonium were the main predictors of V . cholerae abundance in Neusiedler See, while in the shallow alkaline lakes it was organic carbon, conductivity and phosphorus. Based on the obtained concentrations a first estimation of the health risk for visitors of the lake could be performed.