Pathogenic Escherichia coli O157:H7 outbreaks remain a key public health concern, despite continued post-harvest efforts to reduce foodborne pathogens from entering the supply chain. Little research has focused on the potential for biological communities to facilitate the pre-harvest, natural suppression of this pathogen. We combined dung beetle biodiversity sampling, 16S soil community characterization, a large-scale field experiment, and multiple lab microcosm experiments to quantify the relationship between coprophage communities and the biological suppression of pathogenic E. coli. This study took place from 2014 to 2017 on 45 farms throughout CA, OR, and WA, USA.
Results/Conclusions
We found that across 3 different farming systems (conventional, organic, and integrated crop-livestock), dung beetles were ubiquitous at all farms and removed feces from mixed vegetable fields to varying degrees. Furthermore, we found that a more recently introduced invader, Onthophagus nuchicornis, dominates the community when present, and is significantly less effective at both removing feces and suppressing E. coli than other common species. The use of structural equation modeling revealed that organic and integrated crop/livestock farming systems mitigate the landscape level drivers of the invading species. In the lab, beetle species suppressed the pathogen differentially. Additionally, increased soil community diversity was higher on organic and integrated crop/livestock farms than on conventional farms. The differences in these communities, with regards to pathogenic E. coli persistence, will be discussed.