MATERIALS AND METHODS
Microorganism
E. coli O157:H7 (ATCC 35150) was obtained from the
Department of Food and Nutrition at Chung-Ang University Stock cultures were made in tryptic soy broth (TSB;
Difco Laboratories, Detroit, MI) with 20% glycerol (v/v)
and stored at −80C. Active cultures for experiments were
prepared by streaking material from the frozen cultures
onto trypticase soy agar (TSA; Difco Laboratories) plates,
which were incubated for 24 h at 37C. Single colonies were
transferred to TSB and incubated for 24 h at 37C, followed
by a subsequent loop transfer into TSB and overnight incubation
at 37C.Working cultures were maintained on a slant
of TSA and stored at 4C.