Variability in growth responses of non-O157 EHEC isolates in leafy vegetables, sprouted seeds and soil extracts occurs at the isolate level

Bernhard Merget, Ulrich Dobrindt, Ken J Forbes, Norval J C Strachan, Fiona Brennan, Nicola J Holden

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2 Citations (Scopus)


Foods of plant origin are recognised as a major source of food-borne pathogens, in particular for Shigatoxigenic Escherichia coli (STEC). Most work for STEC and plant-based fresh produce has focused on the most prevalent outbreak serogroup, O157. However, non-O157 STEC are an emerging hazard, and as such it is important to characterise aspects within this group that reflect their ability to colonise alternative hosts and habitats relevant to horticultural production. Growth kinetics were quantified for a diverse set of clinical enterohaemorrhagic E. coli isolates in extracts made from different tissues of spinach, lettuce or sprouted seeds, or from soil, to represent association with ready-to-eat fresh produce production. For leafy vegetables, spinach apoplast supported the fastest rates of growth and lettuce root extracts generated the slowest growth rates. Growth rates were similar for the majority of isolates in fenugreek or alfalfa sprouted seed extracts. Monosaccharides were the major driver of bacterial growth. No correlations were found for growth rates between different serotypes or for Shigatoxin gene carriage. Thus, growth rates varied in a plant-dependent and isolate-dependent manner, for all plant or soil extracts tested, indicative of isolate-specific differences in metabolic flexibility. These findings are relevant for risk assessment of non-O157 STEC.

Original languageEnglish
Article numberfnaa030
Number of pages8
JournalFEMS Microbiology Letters
Issue number1
Early online date18 Feb 2020
Publication statusPublished - 2020

Bibliographical note

NJH and JM were supported by a FSA grant [FS101056] and by the Rural & Environment Science & Analytical Services Division of the Scottish Government; BM was supported by a PhD award (James Hutton Institute, Univ. Aberdeen) to NJH, NS, FB and KF; the work in Münster (UD, BM) was supported by the European Commission FP7 ANTIGONE [contract 278976].

We are grateful to Michael Berger (University of Münster) for assistance with growth dynamics measurements.

Conflict of interest disclosure
The authors declare no conflicts of interest


  • EHEC
  • STEC
  • Leafy vegetables
  • soil
  • E. Coli O157:H7
  • leafy vegetables
  • E. coli O157:H7


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