Rapid optical detection of enterococci

Faecal contamination is the main health threat related to water worldwide. The principal monitoring parameters for the microbial safety of drinking and bathing water quality are Escherichia coli and enterococci. These parameters are duly incorporated into legal and regulatory frameworks. Drinking and bathing water are analysed for the presence of E. coli and enterococci using culture methods which take, respectively, one and two days. Because of these long waiting periods, the water distribution sector would like to dispose of rapid methods for the detection of faecal contamination. This need is driven mostly by (1) a desire for rapid detection of contaminations following pipe fractures or planned work on the network, for instance; (2) the negative consequences of having to deal with the long waiting periods following work on the network, before the network sections can be put back into operation; and (3) the wish to monitor the effectiveness of management measures in the event of contamination incidents.


Thanks to advances in microbial measurement methods, the waiting periods for the detection of faecal contamination are becoming shorter. Rapid methods for E. coli have been developed. Since this is not yet the case for enterococci, the rapid detection of E. coli does not offer water companies any cost savings. For this reason only limited use is made of the method. One of the rapid methods for E. coli is BACTcontrol of microLAN. The bacterial species are shown by means of the fluorescence that results from the transformation of the ß-D-glucuronidase enzyme, a fluorogen substrate present in practically all E. coli. The method is automated, rapid, sensitive and reliable.

The objective of the current TKI project is to develop and test a comparable detection method for enterococci that contain the ß-D-glucosidase enzyme. This enzyme reaction is already applied in culture media (see EPA method 1600: Chromocult Enterococci agar, and mEI agar) and in commercial test kits like Enterolert. In principle, it is therefore suitable.


Following a literature review, reference experiments will be conducted in KWR’s laboratory. If the performance of the newly-developed analysis is sufficiently promising, a couple of BACTcontrol tools can be set up on-site to determine the value of the autonomous enterococci analysis in practical situations.


This project intends to make the enzyme-based method in BACTcontrol applicable within the online optical detection, with sufficient speed, sensitivity and reliability. On the basis of the analysis specifications, consideration will be given to the use of online determinations of enterococci and/or E. coli.