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T10-06 Colorimetric Paper-based Detection of Salmonella spp. and Escherichia coli from Artificially Contaminated Irrigation River Water

Wednesday, July 25, 2012: 9:45 AM
Ballroom E (Rhode Island Convention Center)
Bledar Bisha, Colorado State University, Fort Collins, CO
Jana Jokerst, Colorado State University, Fort Collins, CO
Jaclyn Adkins, Colorado State University, Fort Collins, CO
Shannon Coleman, Colorado State University, Fort Collins, CO
Jeffrey Chandler, Colorado State University, Fort Collins, CO
Alma Perez-Mendez, Colorado State University, Fort Collins, CO
Charles Henry, Colorado State University, Fort Collins, CO
Lawrence Goodridge, Colorado State University, Fort Collins, CO
Recorded Presentation
Introduction:  Irrigation water serves as a major source of contamination of fresh produce with bacterial foodborne pathogens including Salmonella spp. or Escherichia coli O157:H7, and timely testing of irrigation water may prevent this contamination. These methods should be sensitive, inexpensive, and have field applicability. Paper-based analytical devices (µPAD) are inexpensive and may provide an effective way of rapidly testing for bacterial pathogens in irrigation water.

Purpose:  The purpose of this study was to develop and evaluate an integrated colorimetric paper-based detection assay for rapid, sensitive and simultaneous detection of Salmonella spp. and the fecal indicator bacteria E. coliin irrigation water.

Methods:  Large volumes (10 l) of irrigation water were spiked with three-strain cocktails of either Salmonella spp. or E. coli at concentrations of 0.1 CFU/ml to 100 CFU/ml. Inoculated samples were concentrated using Moore Swabs (MS) or disposable inline filters (DIF) prior to enrichment in buffered peptone containing selective supplements (25 ml samples of pre-concentrated samples were also enriched). Enrichment was performed at 42°C and colorimetric testing was performed at 8, 12 and 18 hours. µPADs employed the following enzyme/substrate pairs β-galactosidase/chlorphenyl red β-galactopyranoside (CPRG) and esterase/5-bromo-6-chloro-3 indolylcaprylate for colorimetric detection of E. coli and Salmonellaspp., respectively.

Results:  Detection of Salmonella spp. and E. coli was possible at concentrations as low as 0.1 CFU/ml after 8 hours enrichment. Significantly (P < 0.001) more spiked samples were detected following concentration using MS or DIF compared to non-concentrated samples. Within 8 hours, E. coli could be detected at 0.1 CFU/ml only after concentration, while for Salmonella this was true for all concentrations except 100 CFU/ml.

Significance:  The results of this study indicate that µPADs can be used to rapidly and inexpensively detect Salmonella spp. and E. coli in irrigation water, and can be potentially employed in a field setting for rapid and sensitive detection of bacterial pathogens.

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