Date

2022-8-24

Author

İskender, İrem

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The number of outbreaks caused by foodborne pathogens due to contaminated fresh produces has increased worldwide. Escherichia coli is one of the most causative foodborne pathogens. The major transmission way of foodborne pathogens to fresh produce is irrigation water. Once foodborne pathogens are transmitted, the elimination of pathogens from the fresh produce is harder. The most commonly used disinfected agents are chlorine-derived compounds for fresh produce. Yet, usage of them has been related to increasing chemical risk. Thus, the new prevention method for foodborne pathogens that could be applied to the field should be searched. This study aims to investigate an alternative prevention method for the pathogenic E. coli strains; O157:H7, O104:H4, and O26 on freshly consumed garden cresses via irrigation water during vegetation. Firstly, cresses were contaminated with these strains with either 105 CFU/mL and/or 108 CFU/mL via irrigation water. Six groups were designed regarding E. coli contamination and phage treatment days. Next, single and cocktail phage therapies against each strain with the multiplicity of infection (MOI) = -1 or 100 was applied according to the irrigation schedule. On the v 30th day, leaves were collected to count total and biofilm-forming E. coli and compared with their control groups. Furthermore, E. coli adherence on the leaf surface was observed with Scanning Electron Microscopy (SEM). Three different phage therapies, single and cocktail phage with two different MOI values, against E. coli O104:H4 were applied. Single phage therapy against E. coli O104:H4 with MOI = 100 resulted in 0,47 log and 0,33 log reductions in total and biofilm-forming E. coli, respectively. Single phage therapy against E. coli O104:H4 with MOI = -1 led to 2,60 log and 2,45 log reductions in total and biofilm-forming E. coli count, respectively. Phage cocktail therapy against E. coli O104:H4 with MOI = 100 caused 1,06 logs and 0,93 log reductions in total and biofilm-forming E. coli counts, respectively. When phage cocktail therapy against E. coli O157:H7 with MOI = 100 was applied, 1,94 log reduction in total E. coli and 2,35 log reduction in biofilm- forming E. coli count were observed. Single phage therapy against E. coli O26 with MOI = 100 was applied and total and biofilm-forming E. coli counts were reduced by 1,83 logs, and 1,90 logs, respectively. Accordingly, the results of this study show that phage therapy against pathogenic E. coli strains might be a promising application as a biocontrol agent during irrigation on freshly consumed leafy greens on the field. To eradicate E. coli contamination during vegetation by phage therapy, further studies should be conducted.

Subject Keywords

Escherichia coli, foodborne pathogen, bacteriophage, phage therapy, leafy green

URI

https://hdl.handle.net/11511/98627

Collections

Graduate School of Natural and Applied Sciences, Thesis