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Applied and Environmental Microbiology, July 2003, p. 4103-4110, Vol. 69, No. 7
0099-2240/03/$08.00+0 DOI: 10.1128/AEM.69.7.4103-4110.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.
Ingestion of Salmonella enterica Serotype Poona by a Free-Living Nematode, Caenorhabditis elegans, and Protection against Inactivation by Produce Sanitizers
Krishaun N. Caldwell,1 Barbara B. Adler,1 Gary L. Anderson,2 Phillip L. Williams,2 and Larry R. Beuchat1*Center for Food Safety and Department of Food Science and Technology, University of Georgia, Griffin, Georgia 30223-1797,1 Department of Environmental Health Science, University of Georgia, Athens, Georgia 30602-21022
Received 22 November 2002/ Accepted 23 April 2003
Free-living nematodes are known to ingest food-borne pathogens and may serve as vectors to contaminate preharvest fruits and vegetables. Caenorhabditis elegans was selected as a model to study the effectiveness of sanitizers in killing Salmonella enterica serotype Poona ingested by free-living nematodes. Aqueous suspensions of adult worms that had fed on S. enterica serotype Poona were treated with produce sanitizers. Treatment with 20 µg of free chlorine/ml significantly (
= 0.05) reduced the population of S. enterica serotype Poona compared to results for treating worms with water (control). However, there was no significant difference in the number of S. enterica serotype Poona cells surviving treatments with 20 to 500 µg of chlorine/ml, suggesting that reductions caused by treatment with 20 µg of chlorine/ml resulted from inactivation of S. enterica serotype Poona on the surface of C. elegans but not cells protected by the worm cuticle after ingestion. Treatment with Sanova (850 or 1,200 µg/ml), an acidified sodium chlorite sanitizer, caused reductions of 5.74 and 6.34 log10 CFU/worm, respectively, compared to reductions from treating worms with water. Treatment with 20 or 40 µg of Tsunami 200/ml, a peroxyacetic acid-based sanitizer, resulted in reductions of 4.83 and 5.34 log10 CFU/worm, respectively, compared to numbers detected on or in worms treated with water. Among the organic acids evaluated at a concentration of 2%, acetic acid was the least effective in killing S. enterica serotype Poona and lactic acid was the most effective. Treatment with up to 500 µg of chlorine/ml, 1% hydrogen peroxide, 2,550 µg of Sanova/ml, 40 µg of Tsunami 200/ml, or 2% acetic, citric, or lactic acid had no effect on the viability or reproductive behavior of C. elegans. Treatments were also applied to cantaloupe rind and lettuce inoculated with S. enterica serotype Poona or C. elegans that had ingested S. enterica serotype Poona. Protection of ingested S. enterica serotype Poona against sanitizers applied to cantaloupe was not evident; however, ingestion afforded protection of the pathogen on lettuce. These results indicate that S. enterica serotype Poona ingested by C. elegans may be protected against treatment with chlorine and other sanitizers, although the basis for this protection remains unclear.
* Corresponding author. Mailing address: Center for Food Safety and Department of Food Science and Technology, University of Georgia, 1109 Experiment St., Griffin, GA 30223-1797. Phone: (770) 412-4740. Fax: (770) 229-3216. E-mail: lbeuchat{at}uga.edu.
Applied and Environmental Microbiology, July 2003, p. 4103-4110, Vol. 69, No. 7
0099-2240/03/$08.00+0 DOI: 10.1128/AEM.69.7.4103-4110.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.
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