Migration of Caenorhabditis elegans to manure and manure compost and potential for transport of Salmonella newport to fruits and vegetables Stephen J. Kenney a , Gary L. Anderson b , Phillip L. Williams b , Patricia D. Millner c , Larry R. Beuchat a, * a Center for Food Safety and Department of Food Science and Technology, University of Georgia, 1109 Experiment Street, Griffin, GA 30223-1797, USA b Department of Environmental Health Science, University of Georgia, Athens, GA 30602-2102, USA c USDA-ARS, BA, ANRI, SASL, Bldg. 001, Rm. 140, 10300 Baltimore Avenue, Beltsville, MD 20705-2350, USA Received 30 January 2005; received in revised form 11 April 2005; accepted 12 May 2005 Abstract A study was done to determine if a free-living, bacterivorous nematode, Caenorhabditis elegans , migrates to bovine manure, turkey manure, composted bovine manure, composted turkey manure, and manure-amended soil inoculated with Salmonella Newport . Movement of the worm to lettuce, strawberries, and carrots was also studied. C. elegans moved most rapidly to turkey manure and strawberries, with 35% and 60% of worms, respectively, associating with samples within 30 min. Survival and reproduction of C. elegans in test materials were not affected by the presence of S. newport . Bovine manure and bovine manure compost inoculated with S. newport (8.6 log 10 CFU/g) were separately placed in the bottom of a glass jar and covered with a layer of soil (5 cm) inoculated (50 worms/g) or not inoculated with C. elegans . A piece of lettuce, strawberry, or carrot was placed on top of the soil before jars were sealed and held at 20 -C for up to 10 days. In the system using soil inoculated with C. elegans , S. newport initially in bovine manure was detected on the surface of lettuce, strawberry, and carrot samples within 3, 1, and 1 days, respectively. The pathogen was detected on lettuce, strawberry, and carrot within 1, 7, and 1 days, respectively, when initially present in bovine manure compost. With one exception, the pathogen was not detected on the produce over the 10-day incubation period when C. elegans was not present in the soil. Results indicate that C. elegans has the potential for transporting S. newport in soil to the surface of preharvest fruits and vegetables in contact with soil. D 2005 Elsevier B.V. All rights reserved. Keywords: Salmonella newport ; Nematode; Caenorhabditis elegans ; Manure; Compost; Fruit; Vegetable 1. Introduction Numerous outbreaks of foodborne illness associated with the consumption of raw or minimally processed fruits and vegetables contaminated with human enteric pathogens have been documented (Beuchat, 2002; IFT/FDA, 2001; NACMCF, 1999). It is often difficult to determine if contamination is a preharvest or postharvest event. These outbreaks have raised interest in identifying processes through which preharvest fruits and vegetables can become contaminated with food- borne pathogens. Escherichia coli O157:H7, Listeria monocytogenes (Ander- son et al., 2003; Caldwell et al., 2003b), several serotypes of Salmonella enterica (Aballay et al., 2000; Caldwell et al., 2003b; Kenney et al., 2005), Bacillus cereus (Anderson et al., 2003), and Staphylococcus aureus (Sifri et al., 2003) have been reported to be ingested by Caenorhabditis elegans , a free-living, bacterivorous nematode found in soils of temperate regions. The cuticle of live or dead intact worms is thought to provide a physical barrier to protect bacterial cells present in the gut against chemical cleaners and sanitizers applied to processing equipment and some types of raw fruits and vegetables (Caldwell et al., 2003a; Kenney et al., 2004). Chang et al. (1960) reported that chlorinated water is ineffective at killing salmonellae, Shigella sonnei , and viruses in the gut of nematodes isolated from water. It is not uncommon for animal manure and manure compost to be applied to cropland soil as fertilizers. E. coli 0168-1605/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.ijfoodmicro.2005.05.011 * Corresponding author. Tel.: +1 770 412 4740; fax: +1 770 229 3216. E-mail address: lbeuchat@uga.edu (L.R. Beuchat). International Journal of Food Microbiology 106 (2006) 61 – 68 www.elsevier.com/locate/ijfoodmicro