ARS | Publication request: DEVELOPMENT OF A NOVEL PARADIGM FOR THE REAL-TIME MONITORING OF BACTERIAL PATHOGENICITY IN SWINE

Submitted to: American Society of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: July 22, 2002
Publication Date: July 22, 2002
Citation: WILLARD, S., RYAN, P., BAILEY, R., LAWRENCE, M., ESTILL, C., GANDY, S., LAY JR, D.C. DEVELOPMENT OF A NOVEL PARADIGM FOR THE REAL-TIME MONITORING OF BACTERIAL PATHOGENICITY IN SWINE. AMERICAN SOCIETY OF ANIMAL SCIENCE. V. 85(SUPPL 1): ABSTRACT P. 31.

Technical Abstract: The objective of this study was to evaluate whether photonic reporters (e.g., luciferase) incorporated into relevant Salmonella strains could be used as indicators of bacterial infection (both in incidence and severity) within the living pig. To develop this paradigm, neonatal pigs (n = 12) were removed from the sow between 1 and 7 days of age, and placed on an antibiotic-free milk replacer for the duration of the trial. Pigs were anaesthetized for whole body imaging using a Telazol-xylazine-ketamine cocktail, placed in dorsal recumbency and the ventral surface of non-infected pigs imaged (10 min) using a photon counting camera (background image). Following this, one of two experiments were conducted. In Experiment 1, a dose response study was conducted in which pigs were challenged via esophageal intubation with increasing doses of a Salmonella anatum bacterial isolate engineered to express the luciferase protein (Salmonella-lux; 1.5, 4.5 and 7.5 billion CFU). This was done to determine the level of photonic activity (relative units; RU) detectable through the stomach and ventral surfaces of the living pig. In Experiment 2, pigs were imaged (10 min accumulation of photons) pre- and post-challenge (Time 0: Salmonella-lux at 2 billion CFU), the pigs were then recovered and re-imaged at 24, 48 and 72 h post-Salmonella-lux challenge. A 17.7-fold increase (P < .05) in photonic emissions from the addition of 1.5 billion CFU (14,882.7 + 3,965.5 RU) to 7.5 billion CFU (263,596.8 + 95,905.6 RU) of Salmonella-lux was noted in the dose response study. Detectable photonic emissions in the stomach were highest (P < .05) immediately post-infusion (2.5-fold above pre-challenge), while photonic emission from the lower gastrointestinal tract were highest (P < .05) at 24 h (43.7-fold above pre-challenge). By 72 h post-challenge, no difference (P > .10) between the 72 h post-challenge and pre-challenge (background) photonic emissions were noted from infected pigs. In summary, photon-emitting bacteria can be detected through the ventral surfaces of the neonatal pig, providing a unique model from which to assess bacterial pathogenesis in the living pig.