In vivo assessment of effect of fermented milk diet on course of infection in mice with bioluminescent Salmonella

A novel method for assessing the effect of fermented milk and its components on the course of Salmonella infection in live mice is described. Following a period of feeding with whole fermented milk (group W), a cell-free fraction of fermented milk (group S), or saline (group C, control), mice were challenged by oral gavage with a bioluminescent strain of Salmonella Enteritidis. Colonization of the gastrointestinal tract and subsequent infection could be followed by bioluminescent imaging of live mice with a cooled slow-scan CCD camera. Each group of mice was fed for 7 days with the appropriate product. On the eighth day, all mice were orally infected with 10(6) Salmonella cells. On the sixth day after infection, mice in groups W and C showed evidence of disease. No bioluminescent signal was observed for any of the mice in group S. The physical condition of the mice in groups W and S was normal, but some deterioration in the health of the mice in the control group (group C) occur-red. On the eighth day after infection, a weak bioluminescence signal was observed for the mice in group W, but still no signal was observed for any of the mice in group S. Mice in both of these groups appeared normal, but the mice in group C showed strong evidence of infection and marked deterioration in their physical condition accompanied by a bioluminescence signal. This method allows the assessment of the effects of potential nutraceutical agents on the course of infection by foodborne pathogens in live animals in real time.