PCR and the detection of microbial pathogens in water and wastewater

Microbial pathogens are one of the major health risks associated with water and wastewaters. Current methods for the detection of pathogenic viruses, bacteria, protozoa and helminths tend to be inaccurate, time consuming and expensive. As a result, indicator bacteria are commonly used to determine the relative risk of faecal contamination and the possible presence of pathogens in water and wastewaters. Indicator organisms, however, have several disadvantages that make them less than ideal for indicating the possible presence of microbial pathogens. Consequently methods to directly detect microbial pathogens in water and wastewaters are being investigated. Polymerase chain reaction (PCR) is one of the main alternative detection methods being trialed. PCR has been shown to be a rapid, highly sensitive and accurate method. It has already been used experimentally to detect pathogenic viruses, bacteria and protozoa in water and wastewaters. PCR, however, has a number of limitations. One such limitation is the generation of false positives through the detection of naked nucleic acids, non-viable microorganism, or through contamination in the laboratory. Other limitations include inhibition by environmental contaminants and difficulty in quantification. The potential of PCR for the direct detection of microbial pathogens in water and wastewater, as well as the current limitations are discussed below.