ISOLATION AND CHARACTERIZATION OF BACTERIOPHAGE FOR THE CONTROL OF ENTEROHEMORRHAGIC Escherichia coli ON FRESH PRODUCE
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Publisher:The Ohio State University
Series/Report no.:The Ohio State University. Department of Microbiology Honors Theses; 2012
Bacteriophage is a potentially applicable agent for the control of foodborne pathogens. It is particularly relevant to the safety of produce and other minimally processed products since phage application is a non-destructive treatment. The purpose of this study was to evaluate a bacteriophage isolate’s ability to control the host pathogen on produce. A phage active against E. coli O157:H7 EDL933, with a titer of 108 PFU/ml, was isolated from waste water. Application of phage for biocontrol was tested on green peppers and baby spinach leaves. Cut peppers were treated with UV light to eliminate background biota, then spot inoculated with E. coli O157:H7 EDL933 on cut edges and allowed to dry. Baby spinach leaves were spot inoculated with a strain of E. coli O157:H7, that has a green-fluorescent protein (GFP) marker, and no efforts were made to eliminate background biota. Green pepper pieces were treated with a 5-min dip in purified phage lysate while baby spinach leaves were dipped for only 2 min. Treated produce was stored at 4°C, with or without pre-incubation for 4 h at 25°C. Samples were taken periodically over three days to quantify bacterial survivors and phage titer. A control treatment was applied to other samples in the form of a buffer dip, and analyzed at the same time intervals. An additional control set of produce, simply spot inoculated and incubated, were also included. Compared to phage-free rinse, the phage treatment reduced E. coli population on peppers and spinach by 1.5 log CFU/g. The rinse treatment alone reduced E. coli by 1 log; therefore, the total reduction from the rinse with phage lysate was 2.5 log CFU/g, compared to the untreated control. The phage 50 [Type text] titer on fresh produce samples initially increased, but then declined over the remainder of the three-day storage period. These findings suggest the possible utility of using bacteriophage to selectively control pathogens on fresh produce without damaging the product. Further testing is warranted to evaluate phage biocontrol in other food products as well.
Related Item:Academic Major: Chemistry