Date

2022-6-2

Author

Samut, Hilal

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Climate change and its worldwide effects are recognized all over the world. One of the fields where the effect of climate change is observed due to increased mean ambient temperature is food safety. The temperature increase may affect the survival of foodborne pathogens on fresh produce, and not being processed prior to consumption makes fresh produce pose a huge threat to human health. This study was, therefore, planned to present a comprehensive assessment of the impact of climate change, taking its temperature rise scenarios into consideration, on the attachment and biofilm-forming abilities of different pathogenic Escherichia coli serotypes on cress leaves grown under controlled conditions. Enterohemorrhagic E. coli O157:H7, Enteroaggregative E. coli O104:H4 and Enteropathogenic E. coli O26 were inoculated on cress plants at a level of 8 log MPN/ml at different stages during growth to investigate how (i) inoculation time (7, 14, 21 and 28 days post sowing; dps) and (ii) contamination route (seed and leaves) affect the pathogen load on fresh produce under different climate change scenarios (+2, +4, and +6 oC). This present study revealed that temperature increase designed according to mitigation scenarios for climate change did not cause any significant change in the persistence of pathogens studied here on leaf tissue at 30 dps (~4.5 to 7 log MPN/g). In the plants contaminated at a later stage (21 and 28 dps), the populations of E. coli O157:H7, O104:H4 and O26 were higher for all temperatures studied. The results show that E. coli strains used in this study have translocated towards leaf portions from seed and established a significant amount of pathogen load on leaf (~4 to 5.3 log MPN/g). Washing the leaves did not show any significant reduction in the E. coli populations on leaf tissue, which means that the inoculated bacteria have tightly bound to leaf (~3.5 to 7 log MPN/g) and cannot be eliminated by washing practices. Lastly, the residing biofilm structures were detected on the leaf crevices as well as stomata where enteric bacteria could use for further colonization of cress by Scanning Electron Microscope (SEM).

Subject Keywords

Escherichia coli, Biofilm, Attachment, Fresh Produce, Contaminated Irrigation

URI

https://hdl.handle.net/11511/98108

Collections

Graduate School of Natural and Applied Sciences, Thesis