Reduction of fecal shedding of enterohemorrhagic Escherichia coli O157:H7 in lambs by feeding microbial feed supplement

Abstract

Enterohemorrhagic Escherichia coli O157:H7, an emerging food-borne pathogen, has been implicated in several outbreaks in the US. Ruminants, including cattle, sheep and deer are reservoirs of E. coli O157:H7 and fecal shedding of the pathogen forms the vehicle of entry into the human food chain. We studied the efficacy of Lactobacillus acidophilus, Streptococcus faecium, a mixture of L. acidophilus and S. faecium and a mixture of L. acidophilus, S. faecium, Lactobacillus casei, Lactobacillus fermentum and Lactobacillus plantarum in reducing fecal shedding of E. coli O157:H7 by sheep experimentally infected with the pathogen prior to administration with the microbials. Following oral inoculation with 10 10 CFU of E. coli O157:H7, 30 Suffolk ram lambs were blocked by body weight (six blocks of five lambs each) and lambs within the block randomly assigned to five groups. The lamb groups were fed daily for 7 weeks a basal diet without microbial supplement (control) or the basal diet with L. acidophilus or with S. faecium or with a mixture of L. acidophilus and S. faecium or with a mixture of L. acidophilus, S. faecium, L. casei, L. fermentum and L. plantarum. The microbial supplements contained stabilized live naturally occurring bacteria and were mixed with the diet at the rate of 6.0×10 6 CFU per kilogram of diet. Fecal samples were collected weekly and analyzed for E. coli O157:H7 using modified tryptic soy broth with novobiocin as a pre-enrichement broth and cefixim-tellurite sorbitol MacConkey agar (CT-SMAC) as a selective media. E. coli O157:H7 was confirmed by its reaction with O157 and H7 antisera. E. coli O157:H7 was shed continuously and in varying numbers in the feces throughout the 7-week experimental period by all five groups. However, lambs administered a mixture of L. acidophilus, S. faecium, L. casei, L. fermentum and L. plantarum shed significantly lower ( P=0.0211) average number of E. coli O157:H7 (2.3 log 10 CFU per gram of feces per week) than the other lamb groups over the entire experimental period. S. faecium supplemented lambs were comparable ( P=0.0884) to lambs fed a mixture of L. acidophulus and S. faecium in fecal shedding of the pathogen (3.5 versus 4.4 log 10 CFU per gram of feces) but significantly lower ( P=0.0001) than the control lambs (5.6 log 10 CFU per gram of feces) and those supplemented with L. acidophilus (5.5 log 10 CFU per gram of feces) . Average daily gain (ADG) and gain to feed ratio (G:F) were significantly improved ( P=0.0145) by the mixed culture microbials (163.0 g and 0.33 for the control, 186.4 g and 0.37 for L. acidophulus, 168.2 g and 0.36 for S. faecium, 213.6 g and 0.46 for L. acidophulus and S. faecium, and 219.1 g and 0.44, respectively for L. acidophilus, S. faecium, L. casei, L. fermentum and L. plantarum supplemented lambs. The study indicates that supplementing lambs infected with E. coli O157:H7 with S. faecium or a mixture of S. faecium, L. acidophilus, L. casei, L. fermentum and L. plantarum in the diet can reduce total number of E. coli O157:H7 shed in the feces and improve animal meat production performance as well.