Risks and Recommendations Regarding Human Pathogens in Organic Vegetable Production Chains

Hackl, E.

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Organic Eprints

Evelyn Hackl   evelyn.hackl@ait.ac.at Risks and Recommendations Regarding Human Pathogens in Organic Vegetable Production Chains  Background: Outbreaks of disease have increasingly been traced back to the consumption of fresh plant produce contaminated with bacterial pathogens such as pathogenic E. coli or Salmonella   Use  of  manures  and  slurries  as fertilizers  -  important  pathway  of infestation  of  vegetables  with  bacterial pathogens, relevant especially in organic agriculture  Pathogens  already  present  on/in vegetables on the field?  Brandl 2006 Project aim:  to assess and reduce risks of contamination of organically grown vegetables with human pathogenic bacteria Survey of vegetables regarding enteric pathogen infestation in five European countries (AT, D, CH, SE, DK) Mechanisms / factors affecting colonization Assessing current practice and  Harmonization of methods Recommendations Survey of manures / slurries regarding enteric pathogen infestation in five European countries (AT, D, CH, SE, DK) ISO + PCR rbfE (E.coli O157), stx1, stx2 and eae virulence genes (E.coli and others), invA (Salmonella sp.), nuc (Staphylococcus aureus), iap (Listeria monocytogenes), 16S rRNA of Campylobacter spp.   Q1 Country Questionnaires    Farmers‘ Brochure    Leaflet  www.shop.fibl.org    Project  Workshop  Q2 Sampling Questionnaires    Q3 CCP Questionnaire     Most manures contain pathogenic bacteria We found high baseline incidences of human pathogens in manure/slurry samples.  80% of the total manure/slurry samples tested positive for at least one pathogen or EHEC virulence gene, with similar distribution in all countries except O157, Salmonella and Campylobacter. n= 40 samples  per country     Vegetables frequently contain pathogenic bacteria We  found  high  incidences  of  human  pathogens  on/in  vegetables,  but  presumably  low numbers.  Except for one field (carrot), samples that tested positive for one or several pathogens or E.coli virulence genes were collected from all farms. Salmonella and Staphylococcus were the pathogens most often retrieved. Root tip a of spinach plant inoculated with Listeria monocytogenes sv. 1/2a EGD-E GFP tagged 0,0E+00 5,0E+02 1,0E+03 1,5E+03 2,0E+03 2,5E+03 0  20  40  60  80  100 invA gene copy number g−1 soil days The abundance of Salmonella enterica ssp. increases in the soil upon planting of spinach. Planting of spinach     Vegetables are an apt environment for human pathogens Human pathogenic bacteria can colonize vegetable plants internally, and plants promote the growth of pathogens that reside in the soil.     Implementing a safe fertilization management can minimize risks   www.shop.fibl.org   Which  capabilities  must  a  pathogen  have  to  successfully  invade  and  colonize  a  plant environment versus an animal/human environment or both?   Identifying genetic markers that correlate with plant colonization traits will be valuable for the use in epidemiological surveillance programs     What are the genetic traits of vegetable-colonizing human pathogens?  We explore the phenotypic and genotypic characteristics of plant- versus animal/human-associated enteric pathogens (e.g. Salmonella)    Bacteria for biocontrol. Bacterial strains applied as inoculants may render specific plant cultivars less prone to being colonized by plant pathogens as well as by human pathogens.  Bacteria as biofertilizers. Plant beneficial bacteria improve plant growth and health.  Promoting plant interactions with beneficial microorganisms in plant breeding will make better use of natural beneficial interactions, leading to better plant stress tolerance, better plant nutrition, and less colonization by pathogens.     Novel concepts in plant breeding  Interactions of agricultural crops with both pathogenic and beneficial bacteria should be addressed in plant breeding programs  Veronica Arthurson, Kerstin Brankatschk, Dorte Baggesen, Brion Duffy, Claudia Fenzl, Jürgen Friedel, Anton Hartmann, Andreas Hofmann, Lotta Jäderlund, Annette Nygard Jensen, Martin Koller, Bettina Landau, Paul Mäder, Marteen Nauta, Michael Schmid, Agnes Schweinzer, Angela Sessitsch, Ariena van Bruggen, Franco Widmer, Gabriela Wyss Thank you! 

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