In Vitro and In Vivo Investigations of Antimicrobial Treatments to Reduce Escherichia coli O157:H7 in Cattle Manure

In Exp. 1, acetic acid, aluminum sulfate, cetylpyridinium chloride (CPC), lactic acid (LAC), or granulated sulfuric acid was applied to autoclaved manure inoculated with Escherichia coli O157:H7 carrying plasmids encoding green-fluorescent protein (1mL E. coli O157:H7 culture/50 g manure). Treatment with LAC and CPC reduced E. coli O157:H7 by 1.98 and 1.99 log10 cfu/g, respectively. In Exp. 2, LAC or CPC was applied to unautoclaved, inoculated manure incubated at either 5 or 37°C. Regardless of incubation temperature, CPC was most effective at reducing E. coli O157:H7, whereas LAC reduced E. coli O157:H7, but only 48h after treatment application. In Exp. 3, 90 crossbred heifers were blocked by BW and assigned to 15 separate pens (6 heifers/pen). Within blocks, pens (5 pens/treatment) were allocated randomly to 1) untreated pens; 2) pens treated with 1% CPC; or 3) pens treated with 5% LAC. One day after pen treatment and cattle placement, E. coli O157:H7 was reduced by almost 2.0 log10 most probable number/m2 by treating pens with either CPC or LAC, but E. coli O157:H7 counts were similar 28, 50, and 55 d after initial sanitation (treatment × sampling time, P < 0.01). Interestingly, 14 and 28 d after pen placement, heifers in LAC-treated pens tended to have greater (P ≤ 0.10) ADG than heifers in CPC-treated pens. Thus, results of this series of experiments suggest that sanitizing drylot pens before cattle placement may reduce the potential of animal contamination with E. coli O157:H7.