2. Materials and methods
2.1. Bacterial strains and preparation of inocula
Five strains of nalidixic acid-adapted E. coli O157:H7 were used: ATCC 43895 (isolated from raw hamburger meat), E0018 (isolated from bovine faeces), F4546 (isolated from a patient in an alfalfa sprout-associated outbreak), H1730 (isolated from a patient in an outbreak associated with lettuce), and 932 (isolated from a patient with hemorrhagic colitis). Five serovars of S. enterica subsp. enterica were used: Salmonella Enteritidis (isolated from human faeces), Salmonella Typhimurium (isolated from bovine faeces), Salmonella Stanley (isolated from an outbreak associated with alfalfa sprouts), Salmonella Montevideo (isolated from a patient in a tomato-associated outbreak), and Salmonella Newport (isolated from an outbreak associated with alfalfa sprouts).