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

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 s tudied 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 p lantarum in reducing fecal shedding of E. coli O157:H7 by sheep experimenta lly 10(10) CFU of E. coli infected with the pathogen prior to administratio n with the microbials. Following oral inoculation with 10 O157:H7, 30 Suffo lk ram lambs were blocked by body weight (six blocks of five lambs each) an d lambs within the block randomly assigned to five groups. The lamb groups were fed daily for 7 weeks a basal diet without microbial supplement (contr ol) or the basal diet with L. acidophilus or with S. faecium or with a mixt ure of L. acidophilus and S. faecium or with a mixture of L. acidophilus, S . faecium, L. casei, L. fermentum and L. plantarum. The microbial supplemen ts contained stabilized live naturally occurring bacteria and were mixed wi th the diet at the rare of 6.0 x 10(6) CFU per- kilogram of diet. Fecal sam ples were collected weekly and analyzed for E. coli O157:H7 using modified tryptic soy broth with novobiocin as a pre-enrichement broth and cefixim-te llurite sorbitol MacConkey agar (CT-SMAC) as a selective media. E. coli O15 7: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. pla ntarum 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 co mparable (P = 0.0884) to lambs fed a mixture of L. acidophulus and S. faeci um in fecal shedding of the pathogen (3.5 versus 4.4 log(10) CFU per gram o f feces) but significantly lower (P = 0.0001) than the control lambs (5.6 l og(10) CFU per gram of frees) and those supplemented with L. acidophilus (5 .5 log(10) CFU per gram of feces). Average daily gain (ADG) and gain to fee d 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. acid ophulus, 168.2 g and 0.36 for S. faecium, 213.6 g and 0.46 for L. acidophul us and S. faecium, and 219.1 g and 0.44. respectively for L. acidophulus, 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. acidophulus, L. casei, L. fermen tum 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. (C) 2001 Elsevier Science B.V All rights reserved.