Inhibition of Escherichia coli in cultivated cattle manure.

A common practice on Israeli dairy barns comprises daily cultivation of the manure. Cultivation is a mechanical process used to break up and till the manure bedding and it results in a drier and aerated bedding and cleaner cows, which consequently reduces the incidence of mastitis. Cultivation was associated with a shorter survival of Escherichia coli in cultivated manure as compared with noncultivated manure. The objective of the current study was to elucidate the mechanism responsible for the shorter survival duration of E. coli in the cultivated manure. We hypothesized that microorganisms that are antagonistic to E. coli, developing in the cultivated manure, are responsible for this phenomenon. A cow manure derived E. coli strain expressing the green fluorescence protein and antibiotic resistance markers was used to inoculate cow manure in 1.5-L jars. Manure treatments included cultivated and noncultivated manure. Half the jars of each cultivation treatment were autoclave sterilized at 121°C for 1 h on 3 successive days to eliminate from the manure antagonistic microorganisms. Each cultivation-sterilization treatment was performed in triplicate jars. Following sterilization, E. coli numbers in the cultivated and noncultivated manure were comparable, while in the nonsterilized manure the numbers were lower in the cultivated compared with the noncultivated manure. Several fungi isolated from the cultivated manure samples displayed inhibition effect on the tagged E. coli. Antagonistic fungi were also isolated from large-scale cultivated manure samples collected on several dairy farms in Israel. These findings support the notion that manure cultivation might facilitate the development of microorganisms that are antagonistic to E. coli, thus contributing to the general hygiene of the cattle. Identifying the mechanisms by which the antagonistic fungi affect the survival of E. coli in manure could be exploited for improvement of the animal health and for limiting the transmission of zoonotic pathogens to food and water.