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.