The effectiveness of current antimicrobial interventions used in reducing the prevalence or load of Escherichia coli O157 and indicator organisms on cattle hides and carcasses at two commercial beef processing plants was evaluated. Sponge sampling of beef cattle was performed at ve locations from the initial entry of the animals to the slaughter oor to the exit of carcasses from the ''hotbox'' cooler. For each sample, E. coli O157 prevalence was determined and total aerobic bacteria, Enterobacteriaceae, and E. coli O157 were enumerated. E. coli O157 was found on 76% of animal hides coming into the plants, but no carcasses leaving the cooler were identi ed as contaminated with E. coli O157. A positive relationship was seen between the incidence of E. coli O157 in hide samples and that in preevisceration samples. Aerobic plate counts and Enterobacteriaceae counts averaged 7.8 and 6.2 log CFU/100 cm 2 , respectively, on hides, and 1.4 and 0.4 log CFU/100 cm 2 , respectively, on chilled carcasses. Aerobic plate counts and Enterobacteriaceae counts on preevisceration carcasses were signi cantly related to the respective levels on the corresponding hides; the carcasses of animals whose hides carried higher numbers of bacteria were more likely to carry higher numbers of bacteria. Implementation of the sampling protocol described here would allow processors to evaluate the ef cacy of on-line antimicrobial interventions and allow industrywide benchmarking of hygienic practices.Escherichia coli O157:H7 has been a pathogen of concern to the meat processing industry for two decades. Cases of hemorrhagic colitis caused by E. coli O157:H7 were associated with consumption of undercooked ground beef in the early 1980s (26). In the United States during 1992 and 1993, an outbreak of E. coli O157:H7 infection associated with consumption of ground beef caused hundreds of illnesses and four deaths (31). These events led the Food Safety and Inspection Service (FSIS) to declare the E. coli O157:H7 organism an adulterant in ground beef and to require that meat processors establish hazard analysis and critical control point (HACCP) plans for their plants (12). Since this time, numerous intervention strategies focusing on prevention of carcass contamination and decontamination of carcasses have been designed, tested, and put into practice at commercial processing plants.Recent studies have demonstrated that combinations of antimicrobial interventions are more effective at reducing * Author for correspondence. Tel: 402-762-4227; Fax: 402-762-4149; E-mail: arthur@email.marc.usda.gov. † Names are necessary to report factually on available data; however, the U.S. Department of Agriculture neither guarantees nor warrants the standard of the product, and the use of the name by the U.S. Department of Agriculture implies no approval of the product to the exclusion of others that may also be suitable. ‡ Present address: Room 119, Veterinary Diagnostic Center, East Campus, University of Nebraska, Lincoln, NE 68583-0907, USA.surface contami...

Lactic acid bacteria (LAB) were selected on the basis of characteristics indicating that they would be good candidates for a competitive exclusion product (CEP) that would inhibit Escherichia coli O157:H7 in the intestinal tract of live cattle. Fecal samples from cattle that were culture negative for E. coli O157:H7 were collected. LAB were isolated from cattle feces by repeated plating on deMan Rogosa Sharpe agar and lactobacillus selection agar. Six hundred eighty-six pure colonies were isolated, and an agar spot test was used to test each isolate for its inhibition of a four-strain mixture of E. coli O157:H7. Three hundred fifty-five isolates (52%) showed significant inhibition. Seventy-five isolates showing maximum inhibition were screened for acid and bile tolerance. Most isolates were tolerant of acid at pH levels of 2, 4, 5, and 7 and at bile levels of 0.05, 0.15, and 0.3% (oxgall) and were subsequently identified with the API system. Lactobacillus acidophilus, Lactobacillus fermentum, Lactobacillus delbreukii, Lactobacillus salivarius, Lactobacillus brevis, Lactobacillus cellobiosus, Leuconostoc spp., and Pediococcus acidilactici were the most commonly identified LAB. Nineteen strains were further tested for antibiotic resistance and inhibition of E. coli O157:H7 in manure and rumen fluid. Four of these 19 strains showed susceptibility to all of the antibiotics, 13 significantly reduced E. coli counts in manure, and 15 significantly reduced E. coli counts in rumen fluid (P < 0.05) during at least one of the sampling periods. One of the strains, M35, was selected as the best candidate for a CEP. A 16S rRNA sequence analysis of M35 revealed its close homology to Lactobacillus crispatus. The CEP developed will be used in cattle-feeding trials.

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A trial was conducted to study the effects of strain, age, and diet on egg production, egg composition, and yolk fatty acid incorporation. Three strains (six pens of eight hens per strain), [DeKalb Delta (D); Babcock B 300 (B); and Hy-Line W-36 (H)], were subjected to a 10% flax diet + oats from 30 to 50 wk of age. At 50 wk, hens were divided into two groups and one half were kept on flax + oats diets (three pens) or assigned to a second diet of flax - oats (three pens) to 60 wk of age. Eggs were collected at 36 and 58 wk of age for fatty acid and lipid analysis. Strain had an early effect (30 to 50 wk) on egg production with B (85.3) exceeding the other two strains D (81.0) and H (79.1). Strain D had greater feed consumption and egg weight than either B or H. Flax - oats increased percentage shell compared to flax + oats. Strain effect was significant for percentage albumin, which was greatest for D (61.2%) vs H (59.5%) and B (59.4%). Strain D had significantly lower total and percentage yolk lipids than the other two strains. Strain B eggs had more C16:0, but less C18:0 and C18:1 than D and H. No significant effect of strain on C18:2, C18:3, and C22:6 deposition was observed. Percentage C18:0 and C18:1 in the yolk was significantly affected by strain, diet, and strain x diet interaction. Dietary flax + oats increased C18:0 and C18:1 in all strains except H. A significant diet by strain interaction effect occurred such that C18:3 increased in D yolk but decreased in B yolk when flax + oats were fed. Deposition of C18:3 was greater at 58 wk (5.61%) than at 36 wk (2.52%) of age across all strains. Results from these trials indicate that strain, diet, and age can affect yolk lipids and composition.