Escherichia coli: the best biological drinking water indicator for public health protection

Abstract

SUMMARY Public health protection requires an indicator of fecal pollution. It is not necessary to analyse drinking water for all pathogens. Escherichia coli is found in all mammal faeces at concentrations of 10 log 9−1, but it does not multiply appreciably in the environment. In the 1890s, it was chosen as the biological indicator of water treatment safety. Because of method deficiencies, E. coli surrogates such as the ‘fecal coliform’ and total coliforms tests were developed and became part of drinking water regulations. With the advent of the Defined Substrate Technology in the late 1980s, it became possible to analyse drinking water directly for E. coli (and, simultaneously, total coliforms) inexpensively and simply. Accordingly, E. coli was re‐inserted in the drinking water regulations. E. coli survives in drinking water for between 4 and 12 weeks, depending on environmental conditions (temperature, microflora, etc.). Bacteria and viruses are approximately equally oxidant‐sensitive, but parasites are less so. Under the conditions in distribution systems, E. coli will be much more long‐lived. Therefore, under most circumstances it is possible to design a monitoring program that permits public health protection at a modest cost. Drinking water regulations currently require infrequent monitoring which may not adequately detect intermittent contamination events; however, it is cost‐effective to markedly increase testing with E. coli to better protect the public's health. Comparison with other practical candidate fecal indicators shows that E. coli is far superior overall.

ColiSense, today's sample today: A rapid on-site detection of β-d-Glucuronidase activity in surface water as a surrogate for E. coli

“…Fig. 4d shows further data obtained in the same manner for GUS concentrations from 0.02 to 0.42 ng mL 1 .…”

“…Assuming GUS activity of 100 fmol (6-CMU) min 1 calculated per culturable E. coli [12], this meant detection of sample activities below (250 culturable E. coli per 100 mL) (100 fmol (6-CMU) min 1 per culturable E. coli) ¼ 25,000 fmol (6-CMU) min 1 100 mL 1 . To achieve this, the system was designed with a nano-molar 6-CMU fluorescence detection range and sensitivity less than 1 nM 6-CMU.…”

“…coli and Enterococci are widely used as bacterial Faecal Indicators (FI) for recreational waters [1,2]. Table 1 shows the specified maximum limits in Colony Forming Units (CFU) for marine and transitional waters as per the EU Bathing Water Directive 2006/7/EC.…”

A biosensor platform for rapid detection of E. coli in drinking water

“…β-D-glucuronidase (GUD) activity is characteristic of most strains of E. coli and, hence, has been widely used to monitor the presence of this indicator organism in environmental samples, particularly water (Berg and Fiksdal 1988;Edberg et al 2000;Caruso et al 2002). Approximately 97% of E. coli strains have GUD activity and almost all other coliform bacteria lack this enzyme (Caruso et al 2002).…”

Fluorescence resonance energy transfer (FRET)‐based specific labeling ofCryptosporidiumoocysts for detection in environmental samples

“…The water industry has long relied on a multiple barrier approach to reduce pathogens in drinking water, which is routinely checked by the removal of fecal indicator coliform (Escherichia coli) bacteria (6). However, the environmental and chlorine resistance of Cryptosporidium oocysts, along with their low infective dose (7), have resulted in several waterborne outbreaks of cryptosporidiosis where fecal indicator bacteria were absent and conventional water treatment was used (3).…”