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Methods are needed to quickly detect a variety of biological agents that may be releasedinto drinking-water supplies through an intentional contamination incident. In the presentstudy, 13 drinking-water samples were collected from 9 treatment plants to assess thevariability of recoveries of biological agents by culture- or microscopic-based methods andto determine detections of organisms by quantitative polymerase-chain reaction (qPCR)after ultrafiltration. Two 100-L subsamples were collected at each site during eachsampling event: one was seeded in the laboratory with target control organisms; and, thesecond was used to determine the natural incidence of target organisms and serve as anegative control. Six waterborne biological agents were targeted, including: Bacillus anthracis(using B. anthracis Sterne); Burkholderia pseudomallei (using Bu. cepacia as a surrogate);Francisella tularensis (using F. tularensis Live Vaccine Strain); Salmonella typhi; Vibriocholerae; and, Cryptosporidium parvum. Ultrafiltration was used to concentrate allbiological agents simultaneously. Samples were analyzed by qPCR (except for S. typhi)by cultural methods for bacterial pathogens, and by immunomagneticseparation/immunofluorescence assay (IMS/FA) microscopy for C. parvum.Recoveries of biological agents were affected by a variety of factors, including potentialloss of culturability of Burkholderia at lower temperatures, analytical variability ofrecoveries between replicate samples, and problems with qPCR reagents. Recoveries byculture methods for bacteria and IMS/FA for C. parvum were variable between samplesand between some replicate samples, ranging from below detection to greater than 100%.Recoveries were significantly related to water pH, conductivity, and dissolved organiccarbon (DOC) for culture methods but not for IMS/FA. Recoveries by qPCR were notcalculated because of problems quantifying organisms by qPCR in the composite seed.Organisms were detected after ultrafiltration by qPCR; only one sample for B. cepacia wasa false negative by qPCR in regard to the cultural or IMS/FA method. Numbers found byqPCR after ultrafiltration were significantly related or nearly related to numbers found bythe culture methods for B. anthracis, F. tularensis, and V. cholerae but not for Bu. cepaciaand C. parvum. Includes 13 references, tables.

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Edition: Vol. - No. Published: 11/01/2008 Number of Pages: 11 File Size: 1 file , 820 KB