Effectiveness of Bacteriophages Against Biofilm-Forming Shiga-Toxigenic Escherichia coli on Leafy Greens and Cucumbers.

Abstract

Background: Shiga-toxigenic Escherichia coli (STEC) have caused several produce-associated outbreaks, making it challenging to control these pathogens. Bacteriophages could serve as effective biocontrol. Materials and Methods: Spinach, lettuce, and cucumbers, inoculated with STEC (O157, O26, O45, O103, O111, O121, O145), were treated with lytic bacteriophages and stored at 4°C for 3 days. Surviving STEC were enumerated and observed under scanning electron microscope (SEM), and data analyzed using one-way analysis of variance (ANOVA) (p < 0.05). Results: Bacteriophage treatments significantly reduced STEC populations, compared with the control (p < 0.05). On spinach and romaine, STEC O26, O45, and O103 were reduced to undetectable levels and STEC O157, O111, O121, and O145 by ∼2 logs CFU/cm2. Multiserotype phage cocktail reduced STEC on leafy greens by 1.4 CFU/cm2 and on cucumbers by 1.7 logs CFU/cucumber. Clusters of STEC cells, surrounded by extracellular matrix, were observed under SEM of positive control, whereas phage-treated produce surface showed fewer cells, with cellular damage. Conclusions: Bacteriophages could be utilized as biocontrol against STEC on fresh produce.