In Vivo Bioluminescence Imaging for Targeting Acute Hypoxic/Ischemic Small Intestine with Engineered Salmonella Typhimurium

This study aimed at investigating the feasibility of bioluminescence imaging (BLI) with engineered Salmonella typhimurium (Delta ppGpp S. typhimurium) for visualizing acute hypoxic/ischemic bowels. At the start of 12- or 24-h reperfusion, Delta ppGpp S. typhimurium was injected into the lateral tail veins of rats in which three segments of the small intestine were respectively subjected to 2, 3, and 4 h of ischemia. BLI and magnetic resonance imaging were performed at each reperfusion time point. Bioluminescence was exclusively detected in the hypoxic/ischemic segment of the intestine, showing the ability of Delta ppGpp S. typhimurium to specifically target and proliferate in a hypoxic/ischemic area. Serial monitoring of these rat models revealed a progressive increase in bacterial bioluminescence in the ischemic intestines in conjunction with viable bacterial counts. The viable bacterial counts were positively correlated with lactate dehydrogenase levels after 24 h of reperfusion following 3 or 4 h of ischemia as well as interleukin-6 levels after 24 h of reperfusion following 4 h of ischemia. Our findings demonstrated that BLI was able to detect the acute hypoxic/ischemic bowel via monitoring of the distribution, internalization, and activity of administered Delta ppGpp S. typhimurium. These findings may be useful for the early diagnosis of ischemic bowel disease.