Quantification and colonisation dynamics of Escherichia coli O157:H7 inoculation of microgreens species and plant growth substrates

Kathryn M. Wright, Nicola J. Holden (Lead / Corresponding author)

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

Microgreens are edible plants used in food preparation for their appealing flavours and colours. They are grown beyond the point of harvest of sprouted seeds, and normally include the cotyledons and first true leaves. Their method of production is similar to sprouted seeds, which is known to be favourable for growth of microbial pathogens, although there is little data on the potential of food-borne pathogens such as Shigatoxigenic Escherichia coli (STEC) to colonise these plants. We found colonisation of nine different species of microgreen plants by STEC (isolate Sakai, stx-), with high levels of growth over five days, of approximately 5 orders of magnitude, for plants propagated at 21 °C. STEC (Sakai) formed extensive colonies on external tissue, with some evidence for internalisation via stomatal pores. Several factors impacted the level of colonisation: (1) plant tissue type such that for broccoli microgreens, the highest levels of STEC (Sakai) occurred on cotyledons compared to the true leaf and hypocotyl; (2) the route of contamination such that higher levels occurred with contaminated irrigation water compared to direct seed contamination; (3) inoculation dose, although only at low levels of inoculation (3 log10) compared to medium (5 log10) or high (7 log10) levels; (4) environmental factors, including to some extent humidity, but also plant growth substrate types. It was also evident that a starvation response was induced in STEC (Sakai) in low-nutrient plant irrigation medium. Together these data show that microgreens represent a potential hazard of contamination by food-borne pathogens, and to mitigate the risk, they should be considered in the same manner as sprouted seeds.

Original languageEnglish
Pages (from-to)1-10
Number of pages10
JournalInternational Journal of Food Microbiology
Volume273
Early online date8 Mar 2018
DOIs
Publication statusPublished - 20 May 2018

Fingerprint

Escherichia coli O157
plant growth
Escherichia coli
Growth
Seedlings
food pathogens
seeds
Cotyledon
cotyledons
Food
food preparation
Food Contamination
Hypocotyl
broccoli
Edible Plants
Brassica
hypocotyls
irrigation water
starvation
plant tissues

Keywords

  • Journal article
  • Microleaf
  • Microherb
  • Food-borne pathogens
  • Fresh produce
  • Food-borne hazard

Cite this

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title = "Quantification and colonisation dynamics of Escherichia coli O157:H7 inoculation of microgreens species and plant growth substrates",
abstract = "Microgreens are edible plants used in food preparation for their appealing flavours and colours. They are grown beyond the point of harvest of sprouted seeds, and normally include the cotyledons and first true leaves. Their method of production is similar to sprouted seeds, which is known to be favourable for growth of microbial pathogens, although there is little data on the potential of food-borne pathogens such as Shigatoxigenic Escherichia coli (STEC) to colonise these plants. We found colonisation of nine different species of microgreen plants by STEC (isolate Sakai, stx-), with high levels of growth over five days, of approximately 5 orders of magnitude, for plants propagated at 21 °C. STEC (Sakai) formed extensive colonies on external tissue, with some evidence for internalisation via stomatal pores. Several factors impacted the level of colonisation: (1) plant tissue type such that for broccoli microgreens, the highest levels of STEC (Sakai) occurred on cotyledons compared to the true leaf and hypocotyl; (2) the route of contamination such that higher levels occurred with contaminated irrigation water compared to direct seed contamination; (3) inoculation dose, although only at low levels of inoculation (3 log10) compared to medium (5 log10) or high (7 log10) levels; (4) environmental factors, including to some extent humidity, but also plant growth substrate types. It was also evident that a starvation response was induced in STEC (Sakai) in low-nutrient plant irrigation medium. Together these data show that microgreens represent a potential hazard of contamination by food-borne pathogens, and to mitigate the risk, they should be considered in the same manner as sprouted seeds.",
keywords = "Journal article, Microleaf , Microherb , Food-borne pathogens , Fresh produce , Food-borne hazard",
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note = "This work was funded by the Scottish Government's (project numbers RD2.3.3, RD3.1.3) Rural and Environment Science and Analytical Services (RESAS) Division strategic programme (Food Safety) and the Food Standards Agency (grant FS101056).",
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Quantification and colonisation dynamics of Escherichia coli O157:H7 inoculation of microgreens species and plant growth substrates. / Wright, Kathryn M.; Holden, Nicola J. (Lead / Corresponding author).

In: International Journal of Food Microbiology, Vol. 273, 20.05.2018, p. 1-10.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Quantification and colonisation dynamics of Escherichia coli O157:H7 inoculation of microgreens species and plant growth substrates

AU - Wright, Kathryn M.

AU - Holden, Nicola J.

N1 - This work was funded by the Scottish Government's (project numbers RD2.3.3, RD3.1.3) Rural and Environment Science and Analytical Services (RESAS) Division strategic programme (Food Safety) and the Food Standards Agency (grant FS101056).

PY - 2018/5/20

Y1 - 2018/5/20

N2 - Microgreens are edible plants used in food preparation for their appealing flavours and colours. They are grown beyond the point of harvest of sprouted seeds, and normally include the cotyledons and first true leaves. Their method of production is similar to sprouted seeds, which is known to be favourable for growth of microbial pathogens, although there is little data on the potential of food-borne pathogens such as Shigatoxigenic Escherichia coli (STEC) to colonise these plants. We found colonisation of nine different species of microgreen plants by STEC (isolate Sakai, stx-), with high levels of growth over five days, of approximately 5 orders of magnitude, for plants propagated at 21 °C. STEC (Sakai) formed extensive colonies on external tissue, with some evidence for internalisation via stomatal pores. Several factors impacted the level of colonisation: (1) plant tissue type such that for broccoli microgreens, the highest levels of STEC (Sakai) occurred on cotyledons compared to the true leaf and hypocotyl; (2) the route of contamination such that higher levels occurred with contaminated irrigation water compared to direct seed contamination; (3) inoculation dose, although only at low levels of inoculation (3 log10) compared to medium (5 log10) or high (7 log10) levels; (4) environmental factors, including to some extent humidity, but also plant growth substrate types. It was also evident that a starvation response was induced in STEC (Sakai) in low-nutrient plant irrigation medium. Together these data show that microgreens represent a potential hazard of contamination by food-borne pathogens, and to mitigate the risk, they should be considered in the same manner as sprouted seeds.

AB - Microgreens are edible plants used in food preparation for their appealing flavours and colours. They are grown beyond the point of harvest of sprouted seeds, and normally include the cotyledons and first true leaves. Their method of production is similar to sprouted seeds, which is known to be favourable for growth of microbial pathogens, although there is little data on the potential of food-borne pathogens such as Shigatoxigenic Escherichia coli (STEC) to colonise these plants. We found colonisation of nine different species of microgreen plants by STEC (isolate Sakai, stx-), with high levels of growth over five days, of approximately 5 orders of magnitude, for plants propagated at 21 °C. STEC (Sakai) formed extensive colonies on external tissue, with some evidence for internalisation via stomatal pores. Several factors impacted the level of colonisation: (1) plant tissue type such that for broccoli microgreens, the highest levels of STEC (Sakai) occurred on cotyledons compared to the true leaf and hypocotyl; (2) the route of contamination such that higher levels occurred with contaminated irrigation water compared to direct seed contamination; (3) inoculation dose, although only at low levels of inoculation (3 log10) compared to medium (5 log10) or high (7 log10) levels; (4) environmental factors, including to some extent humidity, but also plant growth substrate types. It was also evident that a starvation response was induced in STEC (Sakai) in low-nutrient plant irrigation medium. Together these data show that microgreens represent a potential hazard of contamination by food-borne pathogens, and to mitigate the risk, they should be considered in the same manner as sprouted seeds.

KW - Journal article

KW - Microleaf

KW - Microherb

KW - Food-borne pathogens

KW - Fresh produce

KW - Food-borne hazard

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DO - 10.1016/j.ijfoodmicro.2018.02.025

M3 - Article

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EP - 10

JO - International Journal of Food Microbiology

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SN - 0168-1605

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