Assessment of bathing water quality with anE. coliimmunosensor

Escherichia coli is a Gram-negative, facultative anaerobic, rod-shaped coliform bacterium which is widely used as an indicator of biological safety of water. Currently, 'gold' standard for the detection ofE. coli(and other pathogens) are microbiological culture-based tests. Microbiological tests are very robust for the detection of live pathogens however it can take several days to get the results. A prospective option for the detection ofE. coliin recreational waters in addition to the genetic PCR analyses can be an immunobiosensor, allowing to detectE. coliin 20 min and to issue timely warnings of the safety of water. To compare different methods - microbiological culturing, quantitative PCR analysis and antibody-based immunobiosensor for the analysis of bathing water samples from a popular urban beach Anne Canal in Tartu, Estonia were used. The median value of biosensor results forE. coliwas considerably higher than the results of microbiological cultivation and qPCR: for 40 times, and 4 times, respectively. In addition, the biosensor results were in significant correlation with the number of total coliforms. Considering the current requirements for the biological safety of bathing water, we propose that the indicative safety threshold for bathing water usingimmunosensor analyses is in the range 4 x 10(3)-4 x 10(4)E. colicells/100 mL.