FIG. 1.

Effect of diet on the duration for which E. coli O157:H7 is shed from cattle. Shown is the first day that each of the cattle tested culture negative for E. coli O157:H7 while being fed grain or hay (alfalfa or grass). Each dot represents an individual animal. The inoculum was E. coli O157:H7 strain ATCC 43894 (American Type Culture Collection, Manassas, Va.). Animals were considered culture negative for the bacteria after three consecutive culture-negative analyses, spanning 10 days.