Abstract:

Five minutes after spraying of 5 mL of 1 × 104 CFU/mL E. coli K99, 5 mL of 1 × 109 PFU/mL its phage,
EK99-C, was sprayed into the polluted air and the residual number of viable E. coli K99 was examined at 0.5, 1 h and 2 h
after spraying of phage EK99-C to evaluate the efficacy of phage EK99-C to kill E. coli K99. Meanwhile, the sterilization
efficiencies of five other foodborn pathogens (E. coli K88, Salmonella enteritidis ATCC13076, Salmonella pullorum Spu-16,
Shigella sonnet CMCC51592 and Listeria 2000/47) by their corresponding phages (EK88-4, PSA-6, PSA-116, SS-92 and
FWLLm3) at 2 h after spraying were investigated under the same experimental conditions and concentrations as described
for K99 and EK99-C. The results showed that the residual number of K99 in the plates was close to 0 CFU at 0.5, 1 h and
2 h after spraying, and complete sterilization was achieved at 2 h. Both phage alone and combination could effectively
kill the host bacteria by aerosol spray. Phage PSA-116 had the strongest bactericidal effect, which could kill 100% of the
host bacteria. EK88-4, EK99-C and FWLLm3 killed about 99% of their hosts. However, SS-92 and PSA-6 indicated 80%
bactericidal efficiency on their host bacteria. The residual number of viable bacteria was smaller than 18.50 CFU when the
six phages were mixed in the same volume, providing a bactericidal efficiency above 98.7%.

Key words: phage, cocktail, aerosol spray