Better Identification of Pathogens in Water and Wastes
One of the most important challenges in the field of water and waste treatment is the development of new and better methods to detect waterborne contaminants in both drinking water and environmental water samples. This would make it possible to follow the occurrence and persistence of pathogens in water supplies with greater accuracy, and aid in better reporting of waterborne illnesses. Methods for detecting protozoan pathogens are not very accurate or dependable, and there is a need to find new approaches to this problem. Methods being studied, but not yet perfected for use in this field, include the polymerase chain reaction (PCR) and a variety of fluorescence techniques and radioactivity labeling methods.
Cysts of Giardia and oocysts of Cryptosporidium have been detected by amplifying specific regions of their DNA by PCR. In fact, using this method, it is possible to detect a single cyst of Giardia and to distinguish between species that are pathogenic for humans and those that are not. But problems arise in using these techniques with environmental samples, which contain substances that inhibit the reaction. In addition, the PCR is not quantitative, and it detects DNA from dead organisms as well as living. Studies are needed to make these techniques feasible for use in water testing.
Viruses can also be detected by PCR. The viruses are concentrated by filtration onto membranes, and many viruses can be detected simultaneously by combining gene probes from different groups of viruses. A problem is that viruses inactivated by disinfection procedures are still detected by PCR. To overcome this, viruses may be put into cell cultures to allow them to replicate, indicating that they are not inactivated, and the PCR is done on the infected cell cultures.
Many scientists are trying to improve PCR and other techniques so that they are quantitative and can detect living microorganisms and active viruses in water.
Nester-Anderson-Roberts: I V. Applied Microbiology I 31. Environmental I I © The McGraw-Hill
Microbiology, A Human Microbiology: Treatment of Companies, 2003 Perspective, Fourth Edition Water, Wastes and
Review Questions 799
31.1 Microbiology of Sewage Treatment
Reduction of Biochemical Oxygen Demand
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