Crop plants can become contaminated with human pathogenic bacteria in agro-production systems. Some of the transmission routes of human pathogens to growing plants are well explored such as water, manure and soil, whereas others are less explored such as seeds. Fenugreek seeds contaminated with the entero-hemorrhagic Escherichia coli O104:H4 were suspected to be the principle vectors for transmission of the pathogen to sprouts at the food-borne disease outbreak in Hamburg and surrounding area in 2011. In this study we raised the questions of whether cells of the entero-aggregative E.coli O104:H4 strain 55989 is capable of colonizing developing plants from seeds and if it would be possible that, via plant internalization, these cells can reach the developing embryonic tissue of the next generation of seeds. To address these questions, we followed the fate of strain 55989 and of two other E. coli strains from artiﬁcially contaminated seeds to growing plants, and from developing ﬂower tissue to mature seeds upon proximate introductions to the plant reproductive organs. Escherichiacolistrains diﬀering in origin, adherence properties to epithelial cells, and virulence proﬁle were used in our experimentation to relate eventual diﬀerences in seed and plant colonization to typical E. coli properties. Experiments were conducted under realistic growth circumstances in greenhouse and open ﬁeld settings. Entero-aggregative E. coli strain 55989 and the two other E. coli strains were able to colonize the root compartment of pea plants from inoculated seeds. Inrootsandrhizospheresoil,thestrainscouldpersistuntilthesenescentstageofplantgrowth, whenseedshadripened. Colonizationoftheabove-soilpartswasonlytemporaryatthestartofplant growthforallthreeE.colistrainsand,therefore,theconclusionwasdrawnthattranslocationofE.coli cells via the vascular tissue of the stems to developing pea seeds seems unlikely under circumstances realistic for agricultural practices. Proximate introductions of cells of E. coli strains to developing ﬂowersalsodidnotresultininternalseedcontamination,indicatingthatinternalseedcontamination with E. coli is an unlikely event. The fact that all three E. coli strains showed stronger preference for the root-soil zones of growing pea plants than for the above soil plant compartments, in spite of their diﬀerences in clinical behaviour and origin, indicate that E. coli in general will colonize root compartments of crop plants in production systems.
- entero-aggregative Escherichia coli
- Pisum sativum
- plant production system
- human pathogen
- E. coli O104:H4