P1-218 Biocontrol of Shiga-toxigenic Escherichia coli Using Lytic Phages on Mung Beans and Germinated Sprouts

Monday, July 10, 2017
Exhibit Hall (Tampa Convention Center)
Yiran Ding , University of Manitoba , Winnipeg , Canada
Yan Dong Niu , Alberta Agriculture and Forestry , Lethbridge , Canada
Kim Stanford , Alberta Agriculture , Lethbridge , Canada
Richard Holley , University of Manitoba , Winnipeg , Canada
Tim McAllister , Agriculture and Agri-Food Canada , Lethbridge , Canada
Claudia Narvaez , University of Manitoba , Winnipeg , Canada
Introduction: The big seven Shiga- toxigenic Escherichia coli (STEC) strains, which includes serogroups O26, O45, O111, O103, O121, O145, and O157, are recognized as a major cause of enteric disease worldwide.

Purpose: This study evaluated the effectiveness of seven bacteriophages, isolated from beef cattle, to reduce E. coli serotypes O26, O45, O103, O111, O121, O145, and O157 on mung beans (MB) and sprouts.

Methods: Sixty samples of MB (30g/treatment) were immersed in a cocktail of the top seven STEC strains to achieve a concentration of (10^4CFU/g). MB were treated with chlorinated water (1000 ppm), STEC lytic phage cocktail (10^7 - 10^9 log PFU/ml) for 1 h, or a combination of both treatments. Beans were then stored for at least 72 h before plating and germination. No treatment was applied during germination. STEC survival in both MB and MB sprouts were assessed using total plate count method on MacConkey and Rainbow agars. Survival of different serogroups was evaluated using immunomagnetic separation and latex agglutination.

Results: The phage cocktail showed lytic activity against the seven STEC serogroups to different degrees. There was an interaction among treatment and serogroup (P<0.0001). Four of seven serogroups exhibited more than three log reductions with phage treatment of mung beans (O45, O103, O145, O157). As expected, phage lytic activity improved when combined with chlorinated water. On germinated sprouts, all serogroups survived; only E.coli O111 had more than five log reductions after phage treatment.

Significance: STEC phages were able to reduce the number of STEC in mung beans. These results are promising for future application of phages, in combination with other hurdles, to reduce STEC on sprouting seeds.