Antimicrobial Activity of Phage UDF157lw Against E. coli O157:H7

Escherichia coli O157:H7 (RM9995) was used to evaluate the antimicrobial activity of UDF157lw using the method previously described with subtle modifications (Liao et al., 2022a (link)). In brief, the bacterial culture was prepared in 10 ml of TSB at 37°C for 18 h, followed by dilution in lysogeny broth (LB; Invitrogen, Carlsbad, CA, United States) to reach the final concentration of ~5 log CFU/ml for the experiment. Phage UDF157lw in SM buffer was added to a 4-ml bacterial solution at approximately MOIs of 10, 100, and 1,000. For the control, SM buffer, with the same volume as the phage used in the treatment, was also added to a 4-ml bacterial solution. The control and treatment groups were both incubated at 25°C, and the bacterial counts were quantified at various time points (0, 1, 2, and 4 h) during the incubation. Bacterial counts were quantified on Sorbitol MacConkey agar (BD, Franklin Lakes, NJ, United States) overlayered with thin Tryptic soy agar (TSA) (Thin Agar Layer Method, TAL) (Wu, 2008 (link)).