An evaluation of the use of probiotics and manure composting as strategies to reduce levels of Shiga toxin-producing Escherichia coli in sheep

Healthy ruminants appear to be the main reservoir of Shiga toxin-producing Escherichia coli (STEC). Importantly, this pathogen is shed in faeces of sheep and can cause outbreaks of human illness ranging from diarrhea to hemorrhagic colitis (HC) and hemolytic uremic syndrome (HUS) caused by Shiga toxin-producing E. coli (STEC) have been reported worldwide. The manure of ruminants when used as agricultural fertilizer can serve as a vehicle for STEC contamination of fruits, vegetables, water and soil. The aim of the present study was to evaluate whether the use of probiotic strains of Ruminobacter amylophilus, Ruminobacter succinogenes, Succinovibrio dextrinosolvens, Bacillus cereus sub toyoi, Lactobacillus acidophilus and Enterococcus faecium, supplemented to the daily oral food ration provided to sheep, together with composting of their feces, may be used as a strategy to reduce STEC levels on a farm. The first stage of the present study was performed during a six-week period with a total of 160 sheep distributed among four groups comprised of 40 sheep each. Group A did not receive either STEC or probiotic, Group B received probiotic alone, Group C received STEC plus probiotic and Group D received STEC alone. After the sheep were inoculated, samples of their feces were collected and the number of STEC and E. coli were counted. In the second stage of the study, after the six-week period, all fecal material was composted into four separate heaps. A possible protective effect of the probiotic strains against colonization by STEC was observed. It was also observed that composting was very efficient at eliminating or decreasing the STEC population. Although the number of STEC isolates was effectively decreased in all compost heaps, the Group C derived compost heap was found to have a lower amount of STEC than the Group D derived compost heap. These findings suggest that the use of probiotics, such as lactic bacteria, together with composting manure may be an efficient strategy to decrease the STEC population on a farm.