Figure 1.

Densities of total bacteria and resistance determinants in feces from beef cattle administered chlortetracycline and sulfamethazine (AS700) or no antibiotics in feed, and housed in a beef cattle confined feeding operation for 32 weeks. After 28 weeks, administration of AS700 ceased for 4 weeks to meet mandatory withdrawal requirements. Densities of total bacteria (A), tetB (B), tetC (C), tetL (D), tetM (E), tetO (F), tetW (G), and sul2 (H). Black histogram bars are Campylobacter jejuni densities. Vertical lines with histogram bars represent standard errors of the mean (n = 5). AS700 treatment histogram bars indicated with an asterisk (*) differ (p < 0.050) from the control treatment at the corresponding sample time.