Figure 4. Ceftiofur metabolites confer selective advantage to cef^R E. coli by restricting cef^S population in soil.

Mean colony forming units for presumptively ceftiofur sensitive (cef^S) fecal E. coli in a matrix of sandy soil and feces (25∶1) after addition of urine containing 0 ppm (open circles) or 50 ppm (closed circles) CFM and incubated at 23°C. Bars = s.e.m.