Wednesday, August 13, 2008 - 9:30 AM
S108

Improved hollow-fiber ultrafiltration and real-time PCR detection for the recovery and detection of waterborne microbes

Michael Casteel, Water Quality Division, San Francisco Public Utilities Commission, 1000 El Camino Real, Millbrae, CA 94030

Hollow-fiber ultrafiltration (HFUF) has been shown to recover all classes of waterborne microbes simultaneously. However, little data is available on the ability of HFUF to recover microbes from water of varying quality and for compatibility with various detection methods. Furthermore, a limitation of existing HFUF methods is the time required to process large volumes of water. In the present study, HFUF was evaluated for the recovery of microbial surrogates (coliphage MS2; Escherichia coli B; Bacillus anthracis Sterne spores) and pathogens (Cryptosporidium and Giardia (oo)cysts; E. coli O157:H7; Salmonella typhimurium) spiked in drinking water (DW) or ultrapure (UP) water. Hydraulic modifications, consisting of multiple HFUFs, were compared to existing methods, and detection of microbes was by microscopy, culture, RT-PCR, and/or real-time PCR. Using existing HFUF methods, mean recoveries of MS2, E. coli B, and Giardia in DW were 96%, 56%, and 53%, respectively, and were similar to UP results. Recovery of Cryptosporidium ranged from 50% in UP to 9% in DW. Microbial recoveries did not differ significantly when existing and modified HFUF methods were compared, and sample processing times were reduced by about 1/3 to 1/2 using modified HFUF. Both approaches were compatible with pathogen detection using PCR, but levels of  ≤1000/L were infrequently detectable. Modified HFUF is an improvement over existing HFUF methods and may be used to quickly recover waterborne microbes in environmental and industrial settings. However, additional steps are required for low-level microbial detection, and some secondary concentration procedures may also need modification due to variable water quality.

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