Wild legume root nodules as a potential reservoir for human pathogenic bacteria.

A previous finding by our group (Benhizia et al., 2004) shows that root nodules from wild legumes, besides their natural rhizobium symbionts, can host and multiply bacteria belonging to species pathogenic to humans. These include Enterobacter cloacae, Enterobacter kobei, Escherichia vulneris, Leclercia adecarboxylata, Pantoea agglomerans. As these taxa were repeatedly found in nodules from three plant species, differing by habitat ecophysiology, and harvested in independent natural sites which are spaced apart up to 150 Km from each other, we believe that the phenomenon can be a general feature and have potentially significant impacts for the epidemiology of bacteria of clinical interest. In the sole Italian territory nearly four hundred species of wild leguminous plants are known, whose microbiological interactions are largely unknown. These plants can nevertheless develop abundant root nodules, which are optimal sites for bacterial multiplication. Wild legume distribution can span over a series of habitats, ranging from urban-synanthropic, to agricultural, and to the majority of natural habitats. In light of the above findings, yielding five Enterobacterial taxa of potential danger to humans from the analysis of only three species of wild plants, one could envisage the biomass of wild legumes as possible strategic niche for the survival and active multiplication of clinical pathogens in hosts alternative to mammals.