Summary of Awards to Date

Rapid bacterial testing for on-farm sampling

Date

Jan. 1, 2015 - Dec. 31, 2016

Funding Agency

University of Massachusetts

Amount Awarded

$272,208.00

Investigator

Sam Nugen, Ph.D.
University of Massachusetts

Summary

Due to the sensitive nature of fresh produce, bacteriological safety tests which requires days for results are not practical tools for food safety. In order for a testing plan to present a pragmatic solution, it must be low-cost, reliable, robust and deliver rapid results. Our labs have been developing diagnostics to be used in non-laboratory settings by utilizing bacteriophages. These viruses can attack specific bacteria, replicate within them and then lyse the host while releasing hundreds to thousands of additional viruses. We are proposing the development of a dipstick for the rapid detection of Salmonella spp. in agricultural samples. Following a sample pretreatment, the bacteriopages will be used to infect Salmonella spp. in the sample. Within 45 minutes, the increase in bacteriophage can be quantified with a simple lateral flow device resembling a pregnancy test. Preliminary results for our E. colisensor suggest a very low limit of detection (

Technical Abstract

Recently, the CDC has determined that 46% of foodborne illness is attributable to leafy green vegetables. The recent outbreaks associated with fresh fruits and vegetables have resulted in an increased interest in the ability to rapidly and cost-effectively perform on-farm validation. Test methods designed for on-farm use must be rapid, easy to use and most importantly low-cost.

Currently, there are no pragmatic methods to detect bacteria which can be used in settings with low resources such as a farm. As produce-related foodborne illness continues to be a major concern, there remains a vital need to provide farmers with tools to validate the safety of agricultural water (both rinse and irrigation) which comes in direct contact with food. Testing of this water will soon be required by the Food Safety Modernization Act (FSMA), yet there exists no suitable detection method to be used on-farm.

A combination of bacteriophage amplification and a dipstick assay has been designed for the detection of Salmonella spp. in agricultural water. The assay is designed to be low-cost, easy-to-use and deliver quantitative results within three hours. Successful deployment of the test will empower farmers to perform risk-based testing in addition to periodic testing without incurring significant costs.

The bacteria within the agricultural water will be initially concentrated. The sample is then infected with bacteriophages (a virus that infects only bacteria) specific to Salmonella spp.. This virus is only able to infect and replicate within viable bacteria thus ensuring that non-viable bacteria are not detected. Following the full 30-40 minute replication cycle, the increase in bacteriophage is quantified with a disposable dipstick.

We have been developing dipstick assays for ultra-low detection limits. Our preliminary data suggests that our fluorescent dipstick will have a detection limit ofSalmonellaspp. cells which makes the test ideal for on-farm use and appropriate federal requirements.