<p>Beef steaks between 1 cm and 3 cm-thick were inoculated with <em>Escherichia coli </em>O157:H7 and/or temperature histories were collected at steak centres, at points initially below the central plane, and/or at points 1 cm or 2 cm from steak edges. The steaks were turned over once during grilling when temperatures at the centres reached 30°C or 50°C, or at specified times once, twice or several times during cooking to specified temperatures between 60and 71°C. When steaks were turned over at centre temperature of 30 or 50°C, some points in some steaks did not reach the temperatures specified for steak centres. When steaks turned over at 50°C were cooked to 60, 63 or 65°C, <em>E. coli </em>O157:H7 inoculated at ? 5 log cfu at each point survived at some points in some steaks at numbers ?3 log cfu. When steaks were turned over once during cooking to 71°C, <em>E. coli </em>O157:H7 survived at some points in some steaks turned over after ? 8 min. When steaks were turned over frequently, or twice at appropriate times during cooking to 63°C, no <em>E. coli </em>O157:H7 were recovered from any inoculated steak. Thus, cooking steaks to 71°C may sometimes have only relatively small effects on <em>E. coli </em>O157:H7 in steaks turned over once. However, turning steaks over twice or more during cooking to 63°C can ensure inactivation of large numbers of <em>E. coli</em> O157:H7 at all points in mechanically tenderized steaks.</p>
Rapid Method for Screening Large Numbers of Escherichia coli Colonies for Production of Plasmid-Mediated -Lactamases