Geology topics

H.D. Alan Lindquist

Publications and source records attributed to H.D. Alan Lindquist.

4 recordsLinked to original sources

USGS2013

Reply to “Ranking filter methods for concentrating pathogens in lake water”

Accurately comparing filtration methods is indeed difficult. Our method ( 1 ) and the method described by Borchardt et al. for determining recoveries are both acceptable approaches; however, each is designed to achieve a different research goal. Our study was designed to compare recoveries of multiple microorganisms in surface-water samples. Because, in practice, water-matrix effects come into play throughout filtration, concentration, and detection processes, we felt it important to incorporate those effects into the recovery results.

Applied and Environmental Microbiology↗

USGS2013

Comparison of filters for concentrating microbial indicators and pathogens in lake-water samples

Bacterial indicators are used to indicate increased health risk from pathogens and to make beach closure and advisory decisions; however, beaches are seldom monitored for the pathogens themselves. Studies of sources and types of pathogens at beaches are needed to improve estimates of swimming-associated health risks. It would be advantageous and cost-effective, especially for studies conducted on a regional scale, to use a method that can simultaneously filter and concentrate all classes of pathogens from the large volumes of water needed to detect pathogens. In seven recovery experiments, stock cultures of viruses and protozoa were seeded into 10-liter lake water samples, and concentrations of naturally occurring bacterial indicators were used to determine recoveries. For the five filtration methods tested, the highest median recoveries were as follows: glass wool for adenovirus (4.7%); NanoCeram for enterovirus (14.5%) and MS2 coliphage (84%); continuous-flow centrifugation (CFC) plus Virocap (CFC+ViroCap) for Escherichia coli (68.3%) and Cryptosporidium (54%); automatic ultrafiltration (UF) for norovirus GII (2.4%); and dead-end UF for Enterococcus faecalis (80.5%), avian influenza virus (0.02%), and Giardia (57%). In evaluating filter performance in terms of both recovery and variability, the automatic UF resulted in the highest recovery while maintaining low variability for all nine microorganisms. The automatic UF was used to demonstrate that filtration can be scaled up to field deployment and the collection of 200-liter lake water samples.

Michigan, New York, Ohio, Wisconsin↗

USGS2009

Comparison of traditional and molecular analytical methods for detecting biological agents in raw and drinking water following ultrafiltration

Aims: To compare the performance of traditional methods to quantitative polymerase chain reaction (qPCR) for detecting five biological agents in large-volume drinking-water samples concentrated by ultrafiltration (UF). Methods and Results: Drinking-water samples (100 l) were seeded with Bacillus anthracis, Cryptospordium parvum, Francisella tularensis, Salmonella Typhi, and Vibrio cholerae and concentrated by UF. Recoveries by traditional methods were variable between samples and between some replicates; recoveries were not determined by qPCR. Francisella tularensis and V. cholerae were detected in all 14 samples after UF, B. anthracis was detected in 13, and C. parvum was detected in 9 out of 14 samples. Numbers found by qPCR after UF were significantly or nearly related to those found by traditional methods for all organisms except for C. parvum. A qPCR assay for S. Typhi was not available. Conclusions: qPCR can be used to rapidly detect biological agents after UF as well as traditional methods, but additional work is needed to improve qPCR assays for several biological agents, determine recoveries by qPCR, and expand the study to other areas. Significance and Impact of the Study: To our knowledge, this is the first study to compare the use of traditional and qPCR methods to detect biological agents in large-volume drinking-water samples. ?? 2009 The Society for Applied Microbiology.

Journal of Applied Microbiology↗

USGS2009

Performance of Traditional and Molecular Methods for Detecting Biological Agents in Drinking Water

To reduce the impact from a possible bioterrorist attack on drinking-water supplies, analytical methods are needed to rapidly detect the presence of biological agents in water. To this end, 13 drinking-water samples were collected at 9 water-treatment plants in Ohio to assess the performance of a molecular method in comparison to traditional analytical methods that take longer to perform. Two 100-liter samples were collected at each site during each sampling event; one was seeded in the laboratory with six biological agents - Bacillus anthracis (B. anthracis), Burkholderia cepacia (as a surrogate for Bu. pseudomallei), Francisella tularensis (F. tularensis), Salmonella Typhi (S. Typhi), Vibrio cholerae (V. cholerae), and Cryptospordium parvum (C. parvum). The seeded and unseeded samples were processed by ultrafiltration and analyzed by use of quantiative polymerase chain reaction (qPCR), a molecular method, and culture methods for bacterial agents or the immunomagnetic separation/fluorescent antibody (IMS/FA) method for C. parvum as traditional methods. Six replicate seeded samples were also processed and analyzed. For traditional methods, recoveries were highly variable between samples and even between some replicate samples, ranging from below detection to greater than 100 percent. Recoveries were significantly related to water pH, specific conductance, and dissolved organic carbon (DOC) for all bacteria combined by culture methods, but none of the water-quality characteristics tested were related to recoveries of C. parvum by IMS/FA. Recoveries were not determined by qPCR because of problems in quantifying organisms by qPCR in the composite seed. Instead, qPCR results were reported as detected, not detected (no qPCR signal), or +/- detected (Cycle Threshold or 'Ct' values were greater than 40). Several sample results by qPCR were omitted from the dataset because of possible problems with qPCR reagents, primers, and probes. For the remaining 14 qPCR results (including some replicate samples), F. tularensis and V. cholerae were detected in all samples after ultrafiltration, B. anthracis was detected in 13 and +/- detected in 1 sample, and C. parvum was detected in 9 and +/- detected in 4 samples. Bu. cepacia was detected in nine samples, +/- detected in two samples, and not detected in three samples (for two out of three samples not detected, a different strain was used). The qPCR assay for V. cholerae provided two false positive - but late - signals in one unseeded sample. Numbers found by qPCR after ultrafiltration were significantly or nearly significantly related to those found by traditional methods for B. anthracis, F. tularensis, and V. cholerae but not for Bu. cepacia and C. parvum. A qPCR assay for S. Typhi was not available. The qPCR method can be used to rapidly detect B. anthracis, F. tularensis, and V. cholerae with some certainty in drinking-water samples, but additional work would be needed to optimize and test qPCR for Bu. cepacia and C. parvum and establish relations to traditional methods. The specificity for the V. cholerae assay needs to be further investigated. Evidence is provided that ultrafiltration and qPCR are promising methods to rapidly detect biological agents in the Nation's drinking-water supplies and thus reduce the impact and consequences from intentional bioterrorist events. To our knowledge, this is the first study to compare the use of traditional and qPCR methods to detect biological agents in large-volume drinking-water samples.

Scientific Investigations Report↗