Development and evaluation of large volume sample preparation techniques for microbial detection
Pathogenic microbes can potentially pose a risk to public health, even when they are present at very low levels in the environment. To know what microbes are present in a given water matrix, methods are needed that will effectively remove most of the water while retaining the microbes in a given sample. Once this is done, various analytical techniques can be used to determine if a given microbe is present in the sample. Therefore, effective, low cost techniques to concentrate and purify microbes from large volumes of water are critical. For example, viruses and parasites must often be isolated from 10-1600 liters of source water to be detected. Current sample collection techniques often require expensive filters, such as the Virosorb 1MDS filter, which have only been evaluated with a limited range of microbes.
EPA scientists are investigating several alternative approaches for separating microbes from water more effectively. They are also evaluating techniques that allow different types of microbes, such as viruses, parasites, and bacteria to be isolated. For instance, hollow-fiber ultrafiltration, which concentrates microbes by size, is being evaluated for both viruses and parasites, while the low-cost NanoCeram filter, which is based on charge interactions, is being evaluated for viruses. Scientists are also investigating an EPA developed technique that uses celite (diatomaceous earth) as a way to further concentrate and purify viruses from smaller volumes (30 milliliters -1 liter) of source water.
This work has resulted in the identification of low-cost alternative sample concentration techniques. In the long term, techniques such as hollow-fiber ultrafiltration are expected to be used in conjunction with multipathogen detection devices, opening the door to a multipathogen occurrence method. Such a method would be valuable for many applications, including large-scale occurrence studies such as the one supporting the Unregulated Contaminant Monitoring Rule.