Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: October 28, 2006
Publication Date: December 1, 2006
Citation: Keen, J.E., Durso, L.M., Bono, J.L., Laegreid, W.W. 2006. Oral neomycin therapy reduces shiga-toxigenic E. coli (STEC) O157 fecal shedding in naturally-infected beef cattle [abstract]. 2006 Conference of Research Workers in Animal Disease. p.148. Technical Abstract: Reducing the infection prevalence in livestock of zoonotic food-borne enteric pathogens such as STEC O157 has been largely intractable to date in spite of an intense research effort over the past decade. Based on in vitro antibiotic resistance data generated from diverse bovine STEC O157 isolates suggesting pan-susceptibility to the aminoglycoside neomycin, a field trial using neomycin sulfate at label dose was designed and executed. In August 2004, 100 finishing feedlot steers containing naturally STEC O157-infected cattle were randomized into 20 isolated pens of five cattle each. Ten pens were randomly assigned as controls (untreated) and ten pens were similarly assigned to oral neomycin therapy (label dose of 22 mg/kg PO/day in water from day 0 to day 3). Rectal feces, dorsal midline hide swabs, and oral cavity swabs were collected on days 0, 3, 6 and 9 and cultured for STEC O157. The number of control steers (out of 50) that were fecal STEC O157-positive on days 0, 3, 6 and 9 were 18, 10, 4 and 4, respectively; the respective isolation numbers in 50 neomycin-treated steers were 16, 0, 1 and 1. Using multivariable logistic regression for correlated data to adjust for clustering of steers in pens, untreated control steers were twice as likely to shed STEC O157 vs. neomycin-treated steers during the trial duration (odds ratio = 2.2, 1.1 to 4.4 95% CI). There was a statistically significant decrease in shedding over time in both treatment and control steers. Hide and mouth swab STEC O157 isolation rates were much lower than fecal isolation rates, and were higher (non-significantly) in control compared to neomycin-treated steers. These findings suggest that antibiotic therapy with neomycin sulfate may have utility for targeted late pre-harvest or peri-harvest reduction of STEC O157 infection and contamination in cattle.