Rapid recovery, concentration, and detection of pathogens from vegetable wash water

Investigator: Michael Ladisch (Department of Agricultural and Biological Engineering)

Project Report 2012 - 2013

Food safety outbreaks linked to consumption of leafy greens are an increasing concern, and from an industry perspective it would be ideal to avoid the high costs associated with issuing a recall. Sampling of large volumes of vegetable wash water to detect pathogens that may or may not be present, and if present may be in low numbers, is a major obstacle. New methods to recover and concentrate foodborne pathogens from large sample volumes would greatly facilitate the rapid detection of foodborne pathogens leading to a reduction in the distribution of contaminated foods and the prevention of outbreaks of foodborne illness. ARS-funded researchers at Purdue University's Center for Food Safety Engineering in West Lafayette, Indiana, identified ultra and micro-filtration methods for the rapid concentration and recovery of Salmonella and E.coli O157:H7 from commercial vegetable wash water. The developed cell concentration and recovery system is an automated operation from cell concentration and recovery to cleaning steps (ie, "hands off' operation), which minimize risks of contamination, requires low labor intensity, and results in high recovery rates (75-80%) for the target pathogen. Combined with the post-cleaning step, the whole concentration cycle can be completed within 2 hours. These concentrated samples are then able to be analyzed by conventional or emerging pathogen detection techniques. For example, the concentration method used in conjunction with conventional microbiological plating techniques could detect Salmonella and E.coli O157:H7 in about 24 hours or with DNA-based detection methods (real-time PCR) that could be completed in about 7 hours. The combined approach of concentrating the microorganisms and then testing the concentrated samples for the presence of food pathogens will facilitate timely testing of large volumes of vegetable wash water and reduce the likelihood of distributing contaminated products.

Annual Report