Conditions at the time of inoculation influence survival of attenuated Escherichia coli O157:H7 on field-inoculated lettuce

Moyne, Anne-Laure; Blessington, Tyann; Williams, Thomas R.; Koike, S. T.; Cahn, Michael; Marco, Maria L.; Harris, Linda J.

doi:10.1016/j.fm.2019.103274

Cited by 22 publications

(29 citation statements)

References 42 publications

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“…For instance, a study conducted by McKellar et al ( 36 ), which fit log-linear, Cerf, and Weibull regression models to E. coli O157:H7 die-off data from several different experimental trials, found that the biphasic models (i.e., Cerf and Weibull) best fit the data in most cases, with an initial period of rapid decline followed by a period of tailing. Similar patterns were also seen in several other studies ( 25 , 28 , 31 , 37 , 38 , 40 , 46 , 47 ). Brouwer et al ( 48 ), summarized possible mechanisms of this biphasic pattern, which include heterogeneity in the hardiness of the inoculum population, hardening off (i.e., differential gene expression following exposure to harsh environmental conditions), cells entering the viable but not culturable state, and the effect of cell density.…”

Section: Discussionsupporting

confidence: 90%

“…Several previous studies have also shown that an increase in relative humidity was associated with a decrease in microbial die-off ( 34 , 40 , 49 – 51 ). Additionally, Wood et al ( 41 ) and Moyne et al ( 38 ), saw slower initial die-off after inoculation of spinach and lettuce, respectively, with E. coli O157:H7 when inoculation was performed at night compared to in the morning. It was suggested that this phenomenon was caused by the higher moisture/relative humidity typically experienced at night compared to in the morning.…”

Section: Discussionmentioning

confidence: 99%

“…Additionally, the produce plots in 6 out of the 11 trials did not follow the same die-off pattern (i.e., some of the plots followed a segmented log-linear pattern, and some of the plots followed a log-linear die-off pattern). Previous studies have also indicated that a log-linear die-off pattern is not appropriate for foodborne pathogens, indicator organisms, and surrogates on in-field produce ( 25 – 28 , 31 , 36 – 38 , 40 , 45 , 46 ). For instance, a study conducted by McKellar et al ( 36 ), which fit log-linear, Cerf, and Weibull regression models to E. coli O157:H7 die-off data from several different experimental trials, found that the biphasic models (i.e., Cerf and Weibull) best fit the data in most cases, with an initial period of rapid decline followed by a period of tailing.…”

Section: Discussionmentioning

confidence: 99%

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Effect of Weather on the Die-Off of Escherichia coli and Attenuated Salmonella enterica Serovar Typhimurium on Preharvest Leafy Greens following Irrigation with Contaminated Water

Belias

Sbodio

Truchado

et al. 2020

Appl Environ Microbiol

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The Food Safety Modernization Act (FSMA) includes a time-to-harvest interval following the application of non-compliant water to pre-harvest produce to allow for microbial die-off. However, additional scientific evidence is needed to support this rule. This study aimed to determine the impact of weather on the die-off rate of E. coli and Salmonella on spinach and lettuce under field conditions. Standardized, replicated field trials were conducted in California, New York, and Spain over two years. Baby spinach and lettuce were grown and inoculated with a ∼104 CFU/mL cocktail of E. coli and attenuated Salmonella. Leaf samples were collected at 7 timepoints (0-96h) following inoculation; E. coli and Salmonella were enumerated. The associations of die-off with study design factors (location, produce type, and bacteria) and weather were assessed using log-linear and biphasic segmented log-linear regression. A segmented log-linear model best fit die-off on inoculated leaves in most cases, with a greater variation in the segment 1 die-off rate across trials [-0.46 (95% confidence interval (95% CI): -0.52, -0.41) to -6.99 (95% CI: -7.38, -6.59) log10 die-off/day] compared to the segment 2 die-off rate [0.28 (95% CI: -0.20, 0.77) to -1.00 (95% CI: -1.16, -0.85) log10 die-off/day]. A lower relative humidity was associated with a faster segment 1 die-off and an earlier breakpoint (the time when segment 1 die-off rate switches to the segment 2 rate). Relative humidity was also found to be associated with whether die-off would comply with FSMA's specified die-off rate of -0.5 log10 die-off/day. Importance The log-linear die-off rate proposed by FSMA is not always appropriate, as the die-off of foodborne bacterial pathogens and specified agricultural water quality indicator organisms appear to commonly follow a biphasic die-off pattern with an initial rapid decline followed by a period of tailing. While we observed substantial variation in the net culturable population levels of Salmonella and E. coli at each time point, die-off rate and FSMA compliance (i.e., at least a 2 log10 die-off over 4 days) appear to be impacted by produce type, bacteria, and weather; die-off on lettuce tended to be faster than that on spinach, die-off of E. coli tended to be faster than that of attenuated Salmonella, and die-off tended to become faster as relative humidity decreased. As such, the use of a single die-off rate for estimating time-to-harvest intervals across different weather conditions, produce types, and bacteria should be revised.

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Section: Discussionsupporting

confidence: 90%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Effect of Weather on the Die-Off of Escherichia coli and Attenuated Salmonella enterica Serovar Typhimurium on Preharvest Leafy Greens following Irrigation with Contaminated Water

Belias

Sbodio

Truchado

et al. 2020

Appl Environ Microbiol

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“…Temperature and humidity conditions, and the presence of free water, are important in the multiplication and survival of enteric pathogens (Brandl and Mandrell, 2002;Brandl et al, 2004;Stine et al, 2005;Fonseca et al, 2011;Deblais et al, 2019;Roy and Melotto, 2019) and must be investigated simultaneously with the role of other plant traits. This includes consideration of agricultural practices, such as irrigation type and frequency (Fonseca et al, 2011;Williams et al, 2013;Castro-Ibáñez et al, 2015;Moyne et al, 2019), which may greatly affect the success of any breeding strategy aimed at reducing surface and internal plant colonization by food-borne pathogens. It is also clear that physicochemical stressors in the plant environment (e.g., desiccation and UV radiation) (Jacobs and Sundin, 2001;Lindow and Brandl, 2003;Poza-Carrion et al, 2013) may overshadow other factors in their inhibitory effect on enteric pathogens.…”

Section: Multidisciplinary Approach To Understanding Plant Genotype ×mentioning

confidence: 99%

Breeding Crops for Enhanced Food Safety

et al. 2020

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An increasing global population demands a continuous supply of nutritious and safe food. Edible products can be contaminated with biological (e.g., bacteria, virus, protozoa), chemical (e.g., heavy metals, mycotoxins), and physical hazards during production, storage, transport, processing, and/or meal preparation. The substantial impact of foodborne disease outbreaks on public health and the economy has led to multidisciplinary research aimed to understand the biology underlying the different contamination processes and how to mitigate food hazards. Here we review the knowledge, opportunities, and challenges of plant breeding as a tool to enhance the food safety of plant-based food products. First, we discuss the significant effect of plant genotypic and phenotypic variation in the contamination of plants by heavy metals, mycotoxin-producing fungi, and human pathogenic bacteria. In addition, we discuss the various factors (i.e., temperature, relative humidity, soil, microbiota, cultural practices, and plant developmental stage) that can influence the interaction between plant genetic diversity and contaminant. This exposes the necessity of a multidisciplinary approach to understand plant genotype × environment × microbe × management interactions. Moreover, we show that the numerous possibilities of crop/hazard combinations make the definition and identification of high-risk pairs, such as Salmonella-tomato and Escherichia coli-lettuce, imperative for breeding programs geared toward improving microbial safety of produce. Finally, we discuss research on developing effective assays and approaches for selecting desirable breeding germplasm. Overall, it is recognized that although breeding programs for some human pathogen/toxin systems are ongoing (e.g., Fusarium in wheat), it would be premature to start breeding when targets and testing systems are not well defined. Nevertheless, current research is paving the way toward this goal and this review highlights advances in the field and critical points for the success of this initiative that were discussed during the Breeding Crops for Enhanced Food Safety workshop held 5-6 June 2019 at University of California, Davis.

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“…Однією з причин епідеміологічних негараздів, які пов'язані з умовно-патогенними мікроорганізмами, є їхня висока екологічна пластичність. Здатність бактерій колонізувати філоплану чи корені рослин регулюється багатьма як бактеріальними, так і рослинними факторами (Jechalke et al, 2019;Merget et al, 2019;Moyne et al, 2020). Також встановлено, що існує висока адаптаційна здатність ентеробактерій до різних температур (Merget et al, 2019).…”

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Features of colonization of the phytosphere of wheat seedlings by introduced strains of Escherichia coli

2020

The Journal of v. N. Karazin Kharkiv National University, Series "Biology"

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The paper presents the results of the study of the ability of introduced Escherichia coli strains to colonize different niches of the phytosphere – the rhizosphere, endosphere, and phylosphere of Mersia winter soft wheat seedlings and to influence the plant growth response under these conditions. The ATCC 8739 and clinical E. coli strains were used as the study material, as well as an isolate from the wheat agrocenosis soil. The vegetation experiments were carried out in the factorial chamber of the Department of Plant Physiology and Biochemistry of Plants and Microorganisms of V.N.Karazin Kharkiv National University. The experimental plants were inoculated with suspensions of E. coli strains and soil isolate by watering them in vegetation vessels where seedlings were grown for 10 days. In parallel by the method of successive washes, we analyzed the dynamics of the number of E. coli CFU in the rhizome, endo- and phyllosphere of seedlings. After completion of the experiment, the growth response was analyzed by linear growth and by the integral index of growth and biosynthetic processes – biomass accumulation. The results of experiments show that inoculation with ATCC 8739 and clinical strains of E. coli reduced the germination of wheat seeds and inhibited the growth response. Inoculation with E. coli soil isolate has virtually no effect on seed germination, linear growth, and biomass accumulation by Mersia seedlings. It was found that the number of E. coli bacteria in the phytosphere of wheat plants depended on the type of inoculated strain and differs in different parts of the seedlings phytosphere. The maximum number of E. coli CFU in the phytosphere was detected at the inoculation of plants with the clinical strain, three times less – at exposure to the soil isolate, almost 6 times less – at the inoculation with the standard strain. Differences in the degree of colonization of different parts of the phytosphere were detected at the inoculation of the test seedlings with different strains and soil isolates of E. coli: in the control variant and under the influence of ATCC 8739, the distribution between the rhizo- and endosphere is approximately the same. When the plants were inoculated with the clinical strain, endosphere was colonized, when using the soil isolate – the rhizosphere. In the phyllosphere of the experimental seedlings, only cells of the clinical strain were found in a small number, which indicates its increased adhesive properties. Plant-microbial relationships and the ability of conditionally pathogenic E. coli bacteria to colonize different areas of the plant organism and to use wheat seedlings as an alternative host are discussed.

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Conditions at the time of inoculation influence survival of attenuated Escherichia coli O157:H7 on field-inoculated lettuce

Cited by 22 publications

References 42 publications

Effect of Weather on the Die-Off of Escherichia coli and Attenuated Salmonella enterica Serovar Typhimurium on Preharvest Leafy Greens following Irrigation with Contaminated Water

Effect of Weather on the Die-Off of Escherichia coli and Attenuated Salmonella enterica Serovar Typhimurium on Preharvest Leafy Greens following Irrigation with Contaminated Water

Breeding Crops for Enhanced Food Safety

Features of colonization of the phytosphere of wheat seedlings by introduced strains of Escherichia coli

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