Abstract
Numerous outbreaks of Escherichia coli O157:H7 have been linked to the consumption of leafy vegetables. However, up to the present, little has been known about E. coli O157:H7’s adaptive responses to survival on actively growing (and thus responsive) plants. In this study, whole genome transcriptional profiles were generated from E. coli O157:H7 cells (isolate Sakai, stx-) one hour and two days after inoculation on the leaves of growing butterhead lettuce, and compared with an inoculum control. A total of 273 genes of E. coli O157:H7 Sakai (5.04% of the whole genome) were significantly induced or repressed by at least two-fold (p < 0.01) in at least one of the analyzed time points in comparison with the control. Several E. coli O157:H7 genes associated with oxidative stress and antimicrobial resistance were upregulated, including the iron-sulfur cluster and the multiple antibiotic resistance (mar) operon, whereas the Shiga toxin virulence genes were downregulated. Nearly 40% of the genes with significantly different expression were poorly characterized genes or genes with unknown functions. These genes are of special interest for future research as they may play an important role in the pathogens’ adaptation to a lifestyle on plants. In conclusion, these findings suggest that the pathogen actively interacts with the plant environment by adapting its metabolism and responding to oxidative stress.
Highlights
Leafy vegetables, such as lettuce, are considered a high-risk food since numerous outbreaks with enteric pathogens have been linked to the consumption of these products [1]
The response of E. coli O157:H7 with intact growing young lettuce plants was investigated by the microarray technique to explore the transcriptional changes in E. coli O157:H7
Plants were grown from seeds under conditions that mimic those in commercial lettuce production greenhouses in Belgium; the bacterial strain used for inoculations, E. coli O157:H7 Sakai, previously isolated from a fresh produce outbreak, was cultured at 18 ̋ C and resuspended in a low concentration salt solution to simulate the suboptimal environmental conditions that occur outside the animal host, e.g., in irrigation water
Summary
Leafy vegetables, such as lettuce, are considered a high-risk food since numerous outbreaks with enteric pathogens have been linked to the consumption of these products [1]. (E. coli O157:H7) is one of the pathogens that is frequently involved and is of special interest due to the Agriculture 2016, 6, 6; doi:10.3390/agriculture6010006 www.mdpi.com/journal/agriculture. Agriculture 2016, 6, 6 severe consequences of the illness it may cause. The elderly and immunocompromised persons are at higher risk of severe illness. The bacterium can enter the agricultural environment via animal feces and is able to enter our food chain from this point by, e.g., contaminating the irrigation water used for growing crops, or the use of untreated or non-sufficiently treated manure. As governments promote the consumption of a wide variety of fresh fruit and vegetables, it is important that there is no increased risk for foodborne infections. The understanding of plant-pathogen interactions such as initial adherence, invasion and establishment is essential for the development of effective control measures
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