AUTHOR=Mei Gui-Ying , Tang Joshua , Bach Susan , Kostrzynska Magdalena 

TITLE=Changes in Gene Transcription Induced by Hydrogen Peroxide Treatment of Verotoxin-Producing Escherichia coli O157:H7 and Non-O157 Serotypes on Romaine Lettuce

JOURNAL=Frontiers in Microbiology

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2017.00477

DOI=10.3389/fmicb.2017.00477

ISSN=1664-302X

ABSTRACT=<p>Disease outbreaks of verotoxin-producing <italic>Escherichia coli</italic> (VTEC) O157:H7 and non-O157 serotypes associated with leafy green vegetables are becoming a growing concern. A better understanding of the behavior of VTEC, particularly non-O157 serotypes, on lettuce under stress conditions is necessary for designing more effective control strategies. Hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) can be used as a sanitizer to reduce the microbial load in leafy green vegetables, particularly in fresh produce destined for the organic market. In this study, we tested the hypothesis that H<sub>2</sub>O<sub>2</sub> treatment of contaminated lettuce affects in the same manner transcription of stress-associated and virulence genes in VTEC strains representing O157 and non-O157 serotypes. Six VTEC isolates representing serotypes O26:H11, O103:H2, O104:H4, O111:NM, O145:NM, and O157:H7 were included in this study. The results indicate that 50 mM H<sub>2</sub>O<sub>2</sub> caused a population reduction of 2.4–2.8 log<sub>10</sub> (compared to non-treated control samples) in all six VTEC strains present on romaine lettuce. Following the treatment, the transcription of genes related to oxidative stress (<italic>oxyR</italic> and <italic>sodA</italic>), general stress (<italic>uspA</italic> and <italic>rpoS</italic>), starvation (<italic>phoA</italic>), acid stress (<italic>gadA</italic>, <italic>gadB</italic>, and <italic>gadW</italic>), and virulence (<italic>stx1A</italic>, <italic>stx2A</italic>, and <italic>fliC</italic>) were dramatically downregulated in all six VTEC serotypes (<italic>P</italic> ≤ 0.05) compared to not treated control samples. Therefore, VTEC O157:H7 and non-O157 serotypes on lettuce showed similar survival rates and gene transcription profiles in response to 50 mM H<sub>2</sub>O<sub>2</sub> treatment. Thus, the results derived from this study provide a basic understanding of the influence of H<sub>2</sub>O<sub>2</sub> treatment on the survival and virulence of VTEC O157:H7 and non-O157 serotypes on lettuce.</p>