Persistence of Escherichia coli O157:H7, Salmonella Newport, and Salmonella Poona in the gut of a free-living nematode, Caenorhabditis elegans , and transmission to progeny and uninfected nematodes Stephen J. Kenney a , Gary L. Anderson b , Phillip L. Williams b , Patricia D. Millner c , Larry R. Beuchat a, T 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 3 June 2004; received in revised form 2 September 2004; accepted 1 November 2004 Abstract A study was undertaken to determine the persistence of Escherichia coli O157:H7 and salmonellae in the gut of a free-living nematode, Caenorhabditis elegans , as affected by temperature and relative humidity and to determine if infected worms transmit Salmonella enterica serotype Newport to progeny and uninfected worms. Worms were fed cells of a non-pathogenic strain of E. coli (OP50), E. coli O157:H7, S. enterica serotype Newport, and S. enterica serotype Poona, followed by incubating at 4, 20, or 37 8C for up to 5 days. Initial populations of ingested pathogens significantly increased by up to 2.93 log 10 cfu/worm within 1 day at 20 8C on K agar and remained constant for an additional 4 days. When worms were placed on Bacto agar, populations of ingested pathogens remained constant at 4 8C, decreased significantly at 20 8C, and increased significantly at 37 8C within 3 days. Worms fed E. coli OP50 or S. Newport were incubated at 4 or 20 8C at relative humidities of 33%, 75%, or 98% to determine survival characteristics of ingested bacteria. Fewer cells of the pathogens survived incubation at 33% relative humidity compared to higher relative humidities. Populations of ingested E. coli OP50 and S. Newport decreased by up to 1.65 and 3.44 log 10 cfu/worm, respectively, in worms incubated at 20 8C and 33% relative humidity. Placement together on K agar of adult worms, labeled with green fluorescent protein (gfp) in the pharynx area, that had ingested gfp-labeled S. Newport and uninfected wild type worms resulted in transfer of the pathogen to gut of wild type worms. S. Newport was isolated from C. elegans two generations removed from exposure to the pathogen. Results of these studies show that C. elegans may serve as a temporary reservoir of foodborne pathogens, and could perhaps be a vector for 0168-1605/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.ijfoodmicro.2004.11.043 T 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 101 (2005) 227 – 236 www.elsevier.com/locate/ijfoodmicro