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This Article Full Text (PDF) All Versions of this Article: jas.2008-1470v1 87/7/2239    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Moulton, K. Articles by Willard, S. Search for Related Content PubMed PubMed Citation Articles by Moulton, K. Articles by Willard, S.

Postmortem photonic imaging of lux-modified Salmonella typhimurium within the gastrointestinal tract of swine following oral inoculation in vivo

K. Moulton^*, P. Ryan^*, D. Lay and S. Willard^*

^* Department of Animal and Dairy Sciences, Mississippi State University, Mississippi State, MS 39762 Livestock Behavior Research Unit, USDA-ARS, West Lafayette, IN 47907

swillard{at}ads.msstate.edu

Abstract

The study objective was to monitor Salmonella progression by photonic detection through segments of the gastrointestinal tract following oral inoculation. Pigs (~80 kg) were inoculated orally with 3.1 or 4.1 x 10¹⁰ colony forming units (cfu) of Salmonella typhimurium transformed with plasmid pAK1-lux (S. typh-lux) for a 6-h (n = 6) or 12-h (n = 6) incubation in vivo, and then were euthanized for tissue harvest. Intestinal regions (duodenum, jejunum, ileum, large intestine) were divided into 5 replicates of 4 segments (5 cm) each for imaging. For each replicate, n = 2 segments of each region were intact, while n = 2 segments were opened to expose the digesta. Subsamples of digesta were analyzed to determine actual cfu, and images were analyzed for relative light units per second (RLU/s). At 6 h, a higher (P < 0.05) concentration of emitting bacteria, and consequently a higher (P < 0.05) detection of photonic emissions, was observed in the small intestine than in the large intestine. The correlations (6 h) of photonic emissions in exposed segments to bacterial cfu were r = 0.73, 0.62, 0.56, and 0.52 (P < 0.05) in duodenum, jejunum, ileum, and large intestine, respectively. Photonic emissions were higher (P < 0.05) in intact jejunum, ileum, and large intestine than in the duodenum following a 6-h incubation. At 12 h, a higher (P < 0.05) concentration of emitting bacteria in jejunum and ileum of exposed segments was observed than in duodenum and large intestine of exposed segments. Photonic emissions were higher in ileum than duodenum, jejunum, and large intestine of exposed segments (P < 0.05). The correlations (12-h) of photonic emissions in exposed segments to bacterial cfu were r = 0.71 and 0.62 for jejunum and ileum, respectively (P < 0.05). At 12 h, a higher (P < 0.05) concentration of emitting bacteria in jejunum and ileum of intact segments was observed than in duodenum and large intestine. These data indicate that cfu of introduced bacteria remained higher in the small intestine after 6 and 12 h incubations; we have determined that a minimum of 2.0 x 10⁵ cfu generates detection through these tissues (~1.0 to 21.0 RLU/s). This study demonstrates the feasibility of using biophotonics in research models ex vivo for monitoring the pathogenicity of Salmonella in swine, in place of, or in conjunction with, traditional microbiological assessments and whether a greater level of sensitivity of detection and correlation to actual bacterial concentrations can be achieved.

Key Words: biophotonics • gastrointestinal tract • Salmonella typhimurium • swine