Rapid assessment of oxidative stress induced in microbes to evaluate efficacy of sanitizers in wash water

Rapid assessment of oxidative stress induced in microbes to evaluate efficacy of sanitizers in wash water

Jan. 1, 2013 - Dec. 31, 2014

2013-262

$128,758.00

Nitin Nitin, Ph.D.
University of California, Davis

Glenn Young, Ph.D., Mike McCarthy, Ph.D., Rohan Tikekar, Ph.D.

Final Report

The overall goal of this research proposal is to develop a rapid assessment approach to measure antimicrobial efficacy of sanitizers in wash water. The proposed rapid assessment approach is based on a direct measurement of oxidative stress induced in microbes upon exposure to sanitizers and its correlation with reduction in microbial count. The central hypothesis of the proposed research is that the microbes labeled with cell permeable spin probes will provide a rapid assessment of oxidative stress induced by diverse sanitizing agents and the oxidative stress in the microbes is a sensitive indicator of microbial death induced by sanitizers.  The results of this research will lead to (a) novel approach to rapidly assess the antimicrobial efficacy of diverse sanitizers in presence of organic load based on direct measurement of oxidative stress in microbes; (b) evaluate the differences in oxidative stress response of pathogenic and non-pathogenic organisms induced by sanitizers and their correlations with reduction in microbial count; (c) demonstrate that the proposed assessment approach to evaluate antimicrobial activity of wash water does not require measurement of organic load levels in wash water, thus can lead to a direct measurement of antimicrobial efficacy of sanitizers. 

Technical Abstract

Washing and sanitation is a critical step in the post harvest processing of fresh produce to reduce food safety risks and to improve shelf life of fresh produce.  To reduce risk of cross-contamination of fresh produce with pathogens and to improve process efficiency and control, there is a need to address the following key questions: 1) how can we reliably measure the influence of organic load on antimicrobial efficacy of sanitizers; 2) can a process assessment approach be developed that can measure efficacy of a diverse class of sanitizers including both chlorine and non-chlorine based sanitizers; 3) can non-pathogenic surrogate organisms be used for  assessing the response of pathogenic E.coli 0157-H7 and Salmonella during washing process and can this response be assessed rapidly in a processing environment using benchtop or portable measuring devices?  To address these questions, the proposed research is aimed at developing a novel approach to assess the antimicrobial activity of sanitizers based on direct measurement of oxidative stress induced in microbes by sanitizers. The central hypothesis of the proposed research is that the microbes labeled with cell permeable spin probes will provide a rapid assessment of oxidative stress induced by diverse sanitizing agents and the oxidative stress in the microbes is a sensitive indicator of microbial death induced by sanitizers [1-6].  Furthermore, the proposed approach for assessing the antimicrobial efficacy of sanitizers does not require measurement of organic load levels in wash water. The specific objectives of the proposed research are to: (a) develop magnetic resonance spectroscopy based approaches for rapid assessment of oxidative stress generated in microbes exposed to diverse sanitizers; (b) evaluate correlation between oxidative stress levels in both pathogenic and non-pathogenic microbes and reduction in microbial count; (c) evaluate influence of organic load on the correlation between threshold oxidative stress induced in microbes and reduction in number of microbes. The results of this research will lead to (a) a novel approach to rapidly assess the antimicrobial efficacy of diverse sanitizers based on direct measurement of oxidative stress in microbes; (b) evaluate the differences in oxidative stress response of pathogenic and non-pathogenic organisms induced by sanitizers and their correlations with reduction in microbial count; (c) demonstrate that the proposed assessment approach for evaluating antimicrobial activity of wash water does not require measurement of organic load levels in wash water, thus can lead to a direct measurement of antimicrobial efficacy of sanitizers.