Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/9/2013
Publication Date: 9/2/2013
Publication URL: http://handle.nal.usda.gov/10113/59065
Citation: Borchardt, M.A., Kieke, B.A., Spencer, S.K. 2013. Ranking filter methods for concentrating pathogens in lake water. Applied and Environmental Microbiology. 79:5418-5419.
Interpretive Summary: When assessing waterborne disease risk by measuring pathogen levels in a water source, it is critical to use an effective filtration method. Filters are used to concentrate pathogens from the water before applying laboratory quantification methods. It can be difficult to compare filters for their concentration effectiveness because constituents in the water interfere with the pathogen quantification methods. In addition, because filter effectiveness can depend on water characteristics, those characteristics must be controlled to make a fair “apples-to-apples” comparison. In this paper we describe the technical steps necessary to account for the water effects on pathogen quantification and the effects on filter performance. We also stress that while filter effectiveness is important, scientists must consider other factors, for example, ease-of-use in remote field settings when selecting a filter for meeting the goals of a particular study.
Technical Abstract: Accurately comparing filtration methods for concentrating waterborne pathogens is difficult because of two important water matrix effects on recovery measurements, the effect on PCR quantification and the effect on filter performance. Regarding the first effect, we show how to create a control water matrix, with characteristics identical to the test water matrix, to avoid unequal error biases between qPCR measurements of the recovered pathogen (the dividend of the percent recovery calculation) and the pathogen seed (the divisor). As for the water matrix effect on filter performance, it can be controlled statistically or removed experimentally by simultaneous side-by-side recovery trials. Cost, ease-of-use, requirements for recovery controls, and the capability to achieve study objectives are additional considerations when selecting a filter method.