Submitted to: Applied and Environmental Microbiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/22/2004
Publication Date: 5/1/2005
Citation: Gibbs, D.S., Anderson, G.L., Beuchat, L.R., Carta, L.K., Williams, P.L. 2005. Potential role of diploscapter, a bacterivorous nematode from soil, as a vector of foodborne pathogenic bacteria to pre-harvest fruits and vegetables. Applied and Environmental Microbiology 71: 2433-2347. Interpretive Summary: Foodborne illness is a public health problem affecting millions of people each year. Three kinds of bacteria that may cause human illness include Salmonella, Listeria and a dangerous population of E. coli that may live in manure used for farm fertilizer. One problem is identifying animals or other transporters that may carry these dangerous bacteria from water or manure to fruits and vegetables in contact with field soil. Therefore, this paper provides the first confirmation of the ability of a heat-tolerant roundworm often found in agricultural soil and manure to be attracted to, grow on, and disperse these pathogenic bacteria. The work also shows that this particular roundworm, also known as a nematode, is a hundred times more sensitive to copper than a closely related roundworm commonly used to test environmental poisons. The results are significant because this is the first indication that this kind of roundworm that is difficult to kill by heat may be easy to kill with commonly used copper-containing pesticides. This information may be used by other food safety researchers and regulators to help growers and protect consumers.
Technical Abstract: Diploscapter, a thermotolerant, free-living bacterial-feeding soil nematode commonly found in compost, sewage, and agricultural soil in the United States, was studied to determine its potential role as a vehicle of Salmonella enterica serotype Poona, enterohemorrhagic Escherichia coli O157:H7, and Listeria monocytogenes in contaminating pre-harvest fruits and vegetables. The ability of Diploscapter to survive on agar media, in cow manure, and in composted turkey manure, and to be attracted to, ingest, and disperse foodborne pathogens inoculated into soil or a mixture of soil and composted turkey manure was investigated. Worms survived and reproduced in lawns of S. enterica serotype Poona, E. coli O157:H7, and L. monocytogenes on agar media and in cow manure and composted turkey manure. Attraction of Diploscapter to colonies of pathogenic bacteria on tryptic soy agar within 10, 20, 30, and 60 min and 24 h was determined. At least 85% of the worms initially placed 0.5 - 1 cm away from bacterial colonies migrated to the colonies within 1 h. Within 24 h, at least 90% of the worms were embedded in colonies. The potential of Diploscapter to disperse pathogenic bacteria after exposure to bacteria inoculated into soil or a mixture of soil and composted turkey manure was investigated. Results indicate that Diploscapter can disperse pathogenic bacteria after exposure to pathogens in these milieus and demonstrate its potential to serve as a vector of foodborne pathogenic bacteria in soil, with or without amendment with compost, to the surface of pre-harvest fruits and vegetables in contact with soil.