This study evaluated the utility of defined substrate methodology (DSM) for the enumeration of indicator bacteria in wastewater applications. Two commercial products, Colilert and Enterolert systems (Idexx Laboratories, Westbrook, Maine), were evaluated for variation, false-positive results, and method correlation in both surface waters and treated wastewater effluent. The DSM tests performed as well or better than the traditional methodology. The Colilert total coliform test was also evaluated for its utility in estimating fecal coliforms by incubation at 44.5 Ϯ 0.2°C. The modified DSM total coliform test correlated well to membrane filtration (Pearson correlation coefficient 0.8) for two different sample groups, demonstrating its utility as a screening tool to estimate fecal coliform densities. Water Environ. Res., 74, 131 (2002).

In this study we examined the recovery of Cryptosporidium parvum and Giardia duodenalis from matrices containing various concentrations of dissolved iron. The organisms were recovered by using the immunomagnetic separation-immunofluorescent assay method, and the levels of recovery were compared to the dissolved iron concentrations. The levels of recovery of C. parvum decreased sharply at dissolved iron concentrations greater than 4 mg/liter, while the levels of recovery of G. duodenalis decreased sharply at concentrations greater than 40 mg/liter.

One of the most difficult challenges in the analysis of environmental samples is to separate the organism of interest from a sample that is high in background debris. Immunomagnetic separation (IMS) is one technique that has been developed to accomplish this in a rapid and reliable assay. Immunomagnetic separation (or biomagnetic separation) involves a superparamag-netic, monodispersed, polystyrene microsphere that is coated with a specific ligand. When added to a heterogeneous target suspension, the microspheres bind to the desired target. Using a powerful magnet, the microsphere-target complex is then removed from the suspension. Many different targets of interest can be isolated with this technique, including fungal/bacterial cells or spores, protozoan parasites, cellular and subcellular material, proteins, and nucleic acid products. This wide range of application makes IMS one of the most versatile techniques available for the purification of target products from heterogeneous sample matrices.

Indicator bacteria are the most common way of assessing biological water quality. Indicator bacteria are bacteria that can predict the presence of pathogenic organisms. To be a successful indicator, the following criteria must be met: Indicator bacteria must be easy to cultivate in the laboratory using simple, cost‐effective procedures. Indicator bacteria must be present in high enough concentrations to be readily detectable in a manageable sample volume. Indicator bacteria must effectively predict the risk of illness from exposure to the waterborne pathogens present in contaminated water.