Shedding of foodborne pathogens by Caenorhabditis elegans in compost-amended and unamended soil

A study was done to characterize the shedding of foodborne pathogenic bacteria by Caenorhabditis elegans, evaluate the persistence of worm populations cocultured with foodborne pathogens, and determine if C elegans disperses ingested pathogens in soil as a result of shedding. Escherichia. coli O157:H7, Salmonella enterica serotype Poona, and Listeria monocytogenes, as well as E coli OP50, a non-pathogenic strain, were studied. Synchronous populations of C elegans were fed for 24h on confluent lawns of nalidixic acid-adapted bacteria. C elegans shed viable cells of ingested bacteria on tryptic soy agar supplemented with nalidixic acid (50 mu g ml(-1)) (TSAN) throughout a 5-h post-feeding period. C elegans persisted for up to 10 days by feeding on bacteria that had been shed and grew on TSAN. Eggs harvested from C elegans cultured on shed foodborne pathogens had the same level of viability as those collected from C elegans grown on shed E. coli OP50. After 6-7 days, 78%, 64%, 64%, and 76% of eggs laid by C elegans that had fed on E. coli O157:H7, S. Poona, L. inonocytogenes, and E. coli OP50, respectively, were viable. Worms fed on E. coli O15TH7 were inoculated into soil and soil amended with turkey manure compost. Populations of C elegans persisted in compostamended soil for at least 7 days but declined in unamended soil. E. coli O157:H7 was detected at 4 and 6 days post inoculation in compost-amended and unamended soil, and in unamended soil inoculated with E. coli OP50. Populations of E. coli O157:H7 in soil amended with turkey manure compost were significantly(alpha = 0.05) higher than those in unamended soil. Results indicate that C elegans can act as a vector to disperse foodborne pathogens in soil, potentially resulting in increased risk of contaminating the surface of pre-harvest fruits and vegetables. (c) 2005 Elsevier Ltd. All rights reserved.