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ARS Home » Pacific West Area » Albany, California » Western Regional Research Center » Produce Safety and Microbiology Research » Research » Publications at this Location » Publication #412016

Research Project: Elucidating the Factors that Determine the Ecology of Human Pathogens in Foods

Location: Produce Safety and Microbiology Research

Title: Transcriptional analysis of Escherichia coli O157:H7 and a non-pathogenic E. coli in response to the chlorine treatment regulated by the U.S. Environmental Protection Agency

item Sidelinger, Emilie
item Liao, Yen-Te
item KITAZUMI, AI - Texas Tech University
item DE LOS REYES, BENILDO - Texas Tech University
item Wu, Vivian

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/18/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Sodium hypochlorite is a sanitizer, a powerful oxidizing agent, commonly used for treating irrigation water. However, its potency may be compromised by various environmental conditions, including water turbidity, pH, and temperature, likely contributing to recent Escherichia coli O157:H7 outbreaks in leafy greens. Since the bacterial response to attenuated chlorine effects remains unclear, the objective aims to understand transcriptomic mechanisms regarding the concentration of sodium hypochlorite, regulated by the U.S. Environmental Protection Agency (EPA), used for water treatment to improve the efficacy of chlorination. E. coli O157:H7 strain (RM19259) and non-pathogenic E. coli (TVS353), both with 6 log CFU/ml, were individually treated with 3.5 ppm chlorine solution for 5 and 15 minutes, and the bacterial cultures without chlorination served as a control (also time 0). Both control and treated samples were added with chlorine neutralizer before being subjected to bacterial quantification and RNA extraction for sequencing and transcriptome analysis. The results showed that both E. coli O157:H7 and TVS353 had minimal reductions (0.3 to 0.5 log CFU/ml) after chlorine treatment regardless of exposure time. Transcriptome analysis revealed that treated TVS353 had a rapid quenching of oxidative stress from free chlorine to prevent irreversible damage in proteins and DNAs. Furthermore, the chlorine treatment activated physiological adaptations, such as biofilm formation, osmotic adjustment, and potential deactivation of chlorinated compounds. Post-translational modifications by succinylation were evident, possibly resulting from neutralizing positively charged residues targeted by the treatment. In contrast, the treated E. coli O157:H7 exhibited minimal responses to the same chlorine treatment, highlighting strain-specific differences in adaptation and survival under chlorine exposure. Current findings suggest that hurdle antimicrobial strategies are necessary to enhance the efficacy of the existing chlorination to prevent foodborne pathogens.