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Size Matters: Biological and Food Safety Relevance of Leaf Damage for Colonization of Escherichia coli O157:H7 gfp+

Mulaosmanovic, Emina and Windstam, Sofia and Vågsholm, Ivar and Alsanius, Beatrix (2021). Size Matters: Biological and Food Safety Relevance of Leaf Damage for Colonization of Escherichia coli O157:H7 gfp+. Frontiers in Microbiology. 11 , 608086
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Abstract

This study examined the biological and food safety relevance of leaf lesions for potential invasion of food pathogens into the plant tissue (internalization). This was done by determining the role of artificial leaf damage in terms of damaged leaf area on proliferation of E. coli O157:H7 gfp+. In a two-factorial experiment, unwashed fresh baby leaf spinach (Spinacia oleracea L.) was subjected to four damage levels (undamaged, low, moderate, high damage; factor 1) and three incubation intervals (0, 1, 2 days post-inoculation; factor 2). Individual leaves were immersed for 15 s in a suspension loaded with E. coli O157:H7 gfp+ (106 CFU × mL–1). The leaves were analyzed individually using image analysis tools to quantify leaf area and number and size of lesions, and using confocal laser scanning and scanning electron microscopy to visualize leaf lesions and presence of the introduced E. coli strain on and within the leaf tissue. Prevalence of E. coli O157:H7 gfp+ was assessed using a culture-dependent technique. The results showed that size of individual lesions and damaged leaf area affected depth of invasion into plant tissue, dispersal to adjacent areas, and number of culturable E. coli O157:H7 gfp+ directly after inoculation. Differences in numbers of the inoculant retrieved from leaf macerate evened out from 2 days post-inoculation, indicating rapid proliferation during the first day post-inoculation. Leaf weight was a crucial factor, as lighter spinach leaves (most likely younger leaves) were more prone to harbor E. coli O157:H7 gfp+, irrespective of damage level. At the high inoculum density used, the risk of consumers’ infection was almost 100%, irrespective of incubation duration or damage level. Even macroscopically intact leaves showed a high risk for infection. These results suggest that the risk to consumers is correlated with how early in the food chain the leaves are contaminated, and the degree of leaf damage. These findings should be taken into account in different steps of leafy green processing. Further attention should be paid to the fate of viable, but non-culturable, shiga-toxigenic E. coli on and in ready-to-eat leafy vegetables.

Authors/Creators:Mulaosmanovic, Emina and Windstam, Sofia and Vågsholm, Ivar and Alsanius, Beatrix
Title:Size Matters: Biological and Food Safety Relevance of Leaf Damage for Colonization of Escherichia coli O157:H7 gfp+
Series Name/Journal:Frontiers in Microbiology
Year of publishing :2021
Volume:11
Article number:608086
Number of Pages:15
Associated Programs and Other Stakeholders:Z - SLU - Libray > Odla mera
ISSN:1664-302X
Language:English
Publication Type:Journal article
Article category:Scientific peer reviewed
Version:Published version
Copyright:Creative Commons: Attribution 4.0
Full Text Status:Public
Subjects:(A) Swedish standard research categories 2011 > 1 Natural sciences > 106 Biological Sciences (Medical to be 3 and Agricultural to be 4) > Microbiology (Microbiology in the medical area to be 30109)
(A) Swedish standard research categories 2011 > 4 Agricultural Sciences > 401 Agricultural, Forestry and Fisheries > Food Science
Keywords:enterohemorrhagic, E. coli, food safety, internalization, leafy vegetables, lesions, risk assessment, shiga-toxigenic E. coli, spinach (Spinacia oleracea L.)
URN:NBN:urn:nbn:se:slu:epsilon-p-110753
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-p-110753
Additional ID:
Type of IDID
DOI10.3389/fmicb.2020.608086
Otherhttps://www.frontiersin.org/articles/10.3389/fmicb.2020.608086/full
ID Code:22655
Faculty:LTV - Fakulteten för landskapsarkitektur, trädgårds- och växtproduktionsvetenskap
VH - Faculty of Veterinary Medicine and Animal Science
Department:(LTJ, LTV) > Department of Biosystems and Technology (from 130101)
(VH) > Department of Biomedical Science and Veterinary Public Health
Deposited By: SLUpub Connector
Deposited On:24 Feb 2021 13:06
Metadata Last Modified:25 Feb 2021 05:00

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