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ARS Home » Plains Area » College Station, Texas » Southern Plains Agricultural Research Center » Food and Feed Safety Research » Research » Publications at this Location » Publication #208929

Title: Isolation of Salmonella spp. and bacteriophage active against Salmonella spp. from commercial swine

item Callaway, Todd
item Edrington, Thomas
item Nisbet, David
item McReynolds, Jackson
item Anderson, Robin
item Genovese, Kenneth - Ken
item Harvey, Roger

Submitted to: Safepork
Publication Type: Proceedings
Publication Acceptance Date: 4/18/2007
Publication Date: 5/9/2007
Citation: Callaway, T.R., Edrington, T.S., Brabban, A., Kutter, E., Karriker, L., Stahl, C., Wagstrom, L., Anderson, R.C., Genovese, K.J., McReynolds, J., Harvey, R.B., Nisbet, D.J. 2007. Isolation of Salmonella spp. and bacteriophage active against Salmonella spp. from commercial swine. In: Proceedings of 7th International Safepork Symposium, May 9-11, 2007, Verona, Italy. p. 275-279.

Interpretive Summary: Bacteriophage are bacterial viruses that kill bacteria and are specifically active against certain species or even strains. The food-borne pathogenic bacteria Salmonella lives in the intestinal tract of swine, as do bacteriophage that target Salmonella. However, the incidence of these Salmonella targeting phage in commercial swine is unknown. In the present study we isolated Salmonella from 6.6% of the 360 fecal samples from commercial finishing swine in the central U.S. Phage targeting Salmonella were found on 5 of the 6 farms in 43% of the 360 individual fecal samples. Our results indicate that such phages are widespread in feedlot swine, suggesting that further research into the ecological role of bacteriophage in the gastrointestinal tract is needed.

Technical Abstract: Bacteriophage are viruses that prey on bacteria and may be a potential strategy to reduce foodborne pathogenic bacteria in the gastrointestinal tract of food animals. Phages are fairly common in the gastrointestinal microbial ecosystem of mammals, but the incidence is unknown. If phage are to be effectively ultrabred an intervention strategy, we must understand their role in the microbial ecology of the gut. From a regulatory perspective, knowing incidence of phage is crucial. Therefore the current study was designed to determine the incidence of phage active against Salmonella spp. in the feces of commercial finishing swine in the United States. Fecal samples (n=60) were collected from each of six commercial swine finishing operations. Samples were collected from 10 randomly selected pens throughout each operation. Total number of fecal samples collected in this study was n=360. Salmonella spp. were found in 6.6% of the fecal samples. Salmonella spp. were isolated from only 2 farms and the serotypes represented were Schwarzengrund, Anatum, Ohio and Heidelberg. Bacteriophages were isolated from fecal sample through 2 parallel methods, 1) initial enrichment in Salmonella Typhimurium, or 2) initial enrichment in E. coli B (a strain very sensitive to phages); followed by direct spot-testing against Salmonella Typhimurium. Bacteriophages active against Salmonella Typhimurium were isolated from 1.1% (4/360) of the individual fecal samples when initially enriched in Salmonella Typhimurium. E. coli B-killing phages were isolated from 43.8% (158/360) of the fecal samples but only 2 of these isolates were capable of killing Salmonella Typhimurium. Our results indicate that bacteriophage capable of killing Salmonella Typhimurium are fairly widespread across commercial swine production facilities but may be present at relatively low populations. These results indicate that phage (predator) populations may vary along with Salmonella (prey) populations and that phage could potentially be used as a food safety pathogen reduction strategy.