Fig. 1.

Shedding of E. coli O157:H7 (FRIK47) by two Holstein calves and the impact of feed supplemented with chitosan microparticles (CM). Two calves, animal 15 (A) and animal 75 (B), were test negative for E. coli O157:H7 on three consecutive sample days prior to inoculation. CM were fed to the cows for 6 days starting 1 day before inoculation. The numbers of E. coli O157:H7 bacteria were determined by direct plating. Samples negative by direct plating were tested by immunomagnetic separation (IMS) specific for E. coli O157. Numbers of FRIK47 bacteria in feces (red squares) and swabs of the rectal-anal junction (blue triangles) are plotted. The dashed lines indicate the minimum detection levels of direct plating for fecal (red) and rectal swab (blue) samples. Symbols on the x axis indicate a positive IMS test on the respective days. Arrows indicate inoculation with FRIK47. C designates a day that CM were added to feed.