Purpose: Isolate and characterize bacteriophages from beef cattle environment and evaluate their efficacy against biofilm-forming STEC.
Methods: Fecal (n = 20) and water (n = 67) samples were collected from cattle operations and enriched in NZCYM broth for isolation of bacteriophages. Isolated phages were tested for lytic-activity against STECs (O157:H7, O121, O145, O111, O103, O126, O45), using spot-on-lawn assay. Phages were purified and their morphology observed under transmission electron microscope (TEM). Physiological characteristics were determined for temperature sensitivity (40 to 90°C for 60 min) and pH (0.7 to 11 for 24 h) and storage stability (4, -20 and -80°C for 3 mo.). Effectiveness of bacteriophages against STEC-biofilms on food contact surfaces (stainless steel/high density polyethylene coupons) was also evaluated.
Results: Several phages were isolated that exhibited inhibition towards one O121, one O145 and seven O157:H7 strains. All O157:H7-specific-phages were also effective against O45 and O145. The O121-phage and three O157:H7-phages were identified by TEM as Myoviridae family with a short contractile tail. The other four O157:H7-phages belonged to Siphoviridae family with a long non-contractile tail and the O45-phage belonged to Tectiviridae family with no tail. All phages were very stable at 40-60°C but lost activity at 90°C after 10 minutes, except the O121-phage. The bacteriophages also survived acidic and basic pH range and 3 mo. storage.
Significance: Bacteriophages specific for STECs, with high lytic-activity, pH and thermal stability and that could reduce biofilm formation, could be used as bio-control agents in the meat and produce industry.