Abstract
This study was designed to determine the efficacy of probiotics mixture in the control of Shiga-toxin Escherichia coli (STEC) O157:H7 in experimentally infected lambs. Fifteen Yankassa breed of lambs aged between 3-4 weeks old were used. The lambs were divided into three groups of five lambs each (n=5). Group A: Neither probiotics nor STEC O157:H7 were administered (control), Group B: lambs were administered viable STEC O157:H7 cells at 6 x 108CFU/ml together with daily administration of probiotics mixture at 4.5 x108 CFU/ml, Group C: lambs were administered only viable STEC O157:H7 cells at 6x108 CFU/ml without probiotics. Faecal samples from all the experimental lambs were screened for the presence of STEC O157:H7 before the commencement of this study using Tryptone soy broth (TSB) as an enrichment media and Cefixine-tellurite sorbitol MacConkey agar (CT-SMAC) as a selective media. Following oral inoculation of the lambs with STEC cells, faecal samples were collected once weekly for six weeks, for STEC O157:H7 isolation and enumeration. STEC O157:H7 was confirmed by its reaction with O157 and H7 anti-sera (Wellcomexr). STEC O157:H7 was not shed by lambs in group A (control). However, Group B lambs administered a mixture of probiotics shed significantly lower (P<0.05) counts of STEC cells in the six weeks post-infection than Group C lambs that received only STEC cells without probiotics. In conclusion, the use of probiotics mixture significantly (P<0.05) reduced the faecal shedding of STEC O157:H7. It was therefore recommended that probiotics should be administered to lambs to help control these pathogens. Key words: Shiga-toxin producing Escherichia coli O157:H7, probiotics mixture, cefixime-tellurite Sorbitol MacConkey Agar, tryptone soy broth, anti-sera.  
Highlights
Shiga-toxin-producing Escherichia coli O157:H7 (STEC) is a food borne pathogen primarily transmitted to humans through the consumption of contaminated water or food (Caprioli et al, 2005)
Faecal samples from all the experimental lambs were screened for the presence of Shiga-toxin Escherichia coli (STEC) O157:H7 before the commencement of this study using Tryptone soy broth (TSB) as an enrichment media and Cefixine-tellurite sorbitol MacConkey agar (CT-Sorbitol MacConkey agar (SMAC)) as a selective media
The mean STEC O157:H7 isolates recovered from group B lambs increased significantly (P0.05) to 1.1 x 104 CFU/g during the second week, and progressively decreased to 8 x 103 CFU/g in the third week, 6 x 103 CFU/g in the fourth week, 4 x 103 CFU/g in the fifth week and 2 x 103 CFU/g in the sixth week post-infection (Figure 1)
Summary
Shiga-toxin-producing Escherichia coli O157:H7 (STEC) is a food borne pathogen primarily transmitted to humans through the consumption of contaminated water or food (Caprioli et al, 2005). Pathogenic group of E. coli that has a definite zoonotic origin, not all the STEC strains have been demonstrated to cause disease in humans. Six nonO157 groups have been identified by CDC (2008) to be responsible for over 70% of non-O157 STEC-associated illness (Bosilevac and Koohmaraie, 2011). The predominant STEC serotype associated with outbreaks and sporadic cases of serious STEC illnesses is STEC O157 (Karmali et al, 2010)
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