Preliminary study on the occurrence and risk arising from bacteria internalized in zooplankton in drinking water

摘要

In this study, an environmental sampling campaign was conducted to detect internalized E. colinand C. jejuni bacteria in zooplankton and amoebae samples collected at various stages of threenwater treatment plants in Amsterdam, the Netherlands. Eight sampling locations were selectednand sampling was performed twice, at a two-week interval, at each location. Chlorination wasnused to inactivate free (external) bacteria in the concentrated zooplankton samples and sonicationnwas used to disrupt zooplankton organisms in order to release and recover internalized bacteria.nZooplankton enumeration was performed by microscopy. No internalized E. coli or C. jejuninbacteria were recovered from all of the samples analyzed. The occurrence of internalized E. coli ornC. jejuni bacteria in drinking water was estimated to be lower than one internalized bacteria inn105 zooplankton organisms, as derived from the detection limit of the sampling campaign. Bynusing the QMRA approach and the Beta-Poisson model, a risk of infection of less than 9.2E-6 andn5.9E-5 was estimated for internalized E. coli and C. jejuni in drinking water, respectively. Thisnstudy remains preliminary due to the limited number of samples taken at each location.