Checkoff-funded Research Shows Dramatic Results of Pre-harvest E. coli O157:H7 Interventions

(DALLAS, Texas) All three E. coli O157:H7 interventions – a microbial feed, an antimicrobial feed additive and a vaccine – evaluated in a checkoff-funded live animal trial at Colorado State University demonstrated reductions in E. coli O157:H7 prevalence on hides or in fecal materials.

The study tested Lactobacillus acidophilus probiotic (Bovamine, Nutrition Physiology Corp.), neomycin sulfate (NEOMIX^®, Pfizer Animal Health) and an E. coli O157:H7 bacterin (FDAH Vaccine, Fort Dodge Animal Health). “Eight variations on the treatments were studied since the three interventions were tested singularly and sequentially,” said Dr. Keith Belk, Colorado State University researcher.

The study was conducted in a commercial feedlot located in Eastern Colorado from March 1, 2003 through May 26, 2003.  Researchers collected 1,172 fecal and hide samples from 24 pens of cattle [approximately 200 head of (925 lb) cattle per pen], which were randomly allocated to allow for eight treatment groups, replicated three times.

“The live animal management challenges of this pathogen are complex and enormously different from post-harvest management, and this research moves us one step closer to overcoming these challenges,” said Mike Engler, Ph.D., National Cattlemen’s Beef Association (NCBA) Beef Safety Research Subcommittee Chair and Cactus Feeders President. “This research will lead to a variety of interventions beef producers can use as part of the industry-wide fight against E. coli O157:H7.”

Research Results: Fecal Samples

In the cattle control group, 45.8 percent of the fecal samples tested positive for E. coli O157. After treatment with neomycin sulfate, no fecal samples tested positive for E. coli O157. The Lactobacillus acidophilus and the bacterin vaccine, when administered singularly, resulted in only 13.3 and 14.7 percent of positive tests, respectively. Only 1.3 percent of fecal samples tested positive for E. coli O157 after a combined treatment of neomycin sulfate and Lactobacillus acidophilus.  See attached table.

Research Results:  Hide Samples

In the cattle control group, 40.3 percent of hide samples tested positive for E. coli O157. After treatment with all three interventions (Lactobacillus acidophilus probiotic, neomycin sulfate and E. coli O157:H7 bacterin), only 6.7 percent of the hide samples tested positive for E. coli O157. The same percent (6.7) of samples tested positive following a combined treatment of neomycin sulfate and E. coli O157:H7 bacterin. When treated with neomycin sulfate and Lactobacillus acidophilus in combination, just 7.1 percent of the hide samples tested positive for E. coli O157. See attached table.

Treatment and Status of Interventions

Lactobacillus acidophilus probiotic (Bovamine) was fed for 90 days prior to slaughter. This product can be implemented immediately as an intervention strategy.

Neomycin sulfate (NEOMIX^® AG 325 Medicated Premix ) was fed, according to label, in Type C medicated solid feed at slightly below the recommended dosage. It was fed for three days, then removed from the ration at least 24 hours before harvest to meet the withdrawl requirements.  Neomix is currently approved for treatment and control of colibacillosis (bacterial enteritis). The Food and Drug Administration needs to give direction as to whether control of E. coli O157:H7 would be considered an “extralabel drug use” under a valid veterinarian/client/patient relationship.

E. coli O157:H7 bacterin was administered two times during the study, 30 days apart. Since the vaccine is still in the experimental stage, USDA-FSIS granted slaughter permits for the cattle vaccinated in this study. The checkoff-funded research builds the case for a possible vaccine solution using E. coli O157:H7 bacterin.

Additionally, four treatments using intervention strategies in combination also were evaluated.

“This checkoff-funded research shows some of the most dramatic pre-harvest reductions of E. coli O157:H7 to date and it supports building multiple interventions and hurdles against this pathogen,” said Dr. Bo Reagan, vice president of research and knowledge management, National Cattlemen’s Beef Association, which manages safety research on behalf of the Cattlemen’s Beef Board. At least $65 million in pre- and post-harvest pathogen intervention research and strategies have been conducted by industry and government since the first major E. coli O157:H7 outbreak ten years ago.

TABLE:   Percent prevalence (and parenthetically, percent less than control)
of positive E. coli O157 isolates from hide or fecal samples collected from cattle exposed to one of eight treatments.