Coliform Group and Fecal Coliform Organisms as Indicators of Pollution in Drinking Water

Biological Indicators for Fecal Pollution Detection and Source Tracking: A Review

Fecal pollution, commonly detected in untreated or less treated sewage, is associated with health risks (e.g., waterborne diseases and antibiotic resistance dissemination), ecological issues (e.g., release of harmful gases in fecal sludge composting, proliferative bacterial/algal growth due to high nutrient loads) and economy losses (e.g., reduced aqua farm harvesting). Therefore, the discharge of untreated domestic sewage to the environment and its agricultural reuse are growing concerns. The goals of fecal pollution detection include fecal waste source tracking and identifying the presence of pathogens, therefore assessing potential health risks. This review summarizes available biological fecal indicators focusing on host specificity, degree of association with fecal pollution, environmental persistence, and quantification methods in fecal pollution assessment. The development of practical tools is a crucial requirement for the implementation of mitigation strategies that may help confine the types of host-specific pathogens and determine the source control point, such as sourcing fecal wastes from point sources and nonpoint sources. Emerging multidisciplinary bacterial enumeration platforms are also discussed, including individual working mechanisms, applications, advantages, and limitations.

Evaluation of the Autoanalysis Colilert test for detection and enumeration of total coliforms

The Autoanalysis Colilert (AC) test was compared with the membrane filter (MF), 10-tube multiple-tube fermentation (MTF) technique, and the presence-absence test as described in Standard Methods for the Examination of Water and Wastewater for the detection and enumeration of total coliforms in water. The methods were evaluated with 31 samples from seven different sources. Each sample was analyzed by each of the techniques, using replicate 100-ml sample volumes. A total of 582 confirmed tubes were positive by the MTF test, and 533 tubes were positive by the AC test. Statistical analysis of the most-probable-number comparability data showed a statistically significant difference in the number of positive tubes, with the MTF test resulting in more positive tubes. There were no statistically significant differences in precision between the two methods. All the methods were comparable in detection of total coliforms. Levels of heterotrophic bacteria generally encountered in drinking water did not interfere with detection or enumeration of coliforms by the AC test.

Impact of verification media and resuscitation on accuracy of the membrane filter total coliform enumeration technique

Verification of membrane filter total coliform colonies was compared in lauryl tryptose broth, and m-LAC broth primary media and brilliant green-lactose-bile broth and EC broth secondary media. Verification in m-LAC broth yielded the greatest number of aerogenic isolates for both untreated surface water and drinking water samples. Verification in brilliant green-lactose-bile broth increased the number of false-negative reactions. At least 90% of the isolates aerogenic in primary verification media and anaerogenic in brilliant green-lactose-bile broth were representative of the coliform genera. The addition of a resuscitation step in the membrane filter technique did not yield greater numbers of verified coliforms per sample. Verification of both typical and atypical colonies in m-LAC broth resulted in a 10-fold increase in coliform numbers from untreated surface water. With drinking water, verification of both colony types resulted in an increase from less than 1 coliform per 100 ml to greater than 1/100 ml. A single-step verification in m-LAC broth is proposed as a more rapid and sensitive coliform verification procedure than the standard technique.