In vivo bioluminescent imaging of a new model of infectious complications in head-injury rats.

Infectious complications are responsible for 10-25% of mortality in head-injured patients. In the present work we developed a model of infectious complications in head-injury rats using Escherichia coli (E. coli) with a stable copy of the lux operon, and monitored the infection in vivo by optical imaging. Rats were randomized into three groups: AL (healthy rats), HI (head-injury rats), and HI-EC (HI rats+single enteral bolus of E. coli, 1.3×10(9)/rat given 2 days after HI). Infection was evaluated with a camera at 2 and 6 h after E. coli challenge. Blood and organs were sampled to assess biological parameters. HI was associated with body weight loss, muscle atrophy, and plasma amino acid disturbances, in particular glutamine depletion (AL 919±37 versus HI 647±25 and HI-EC 717±20 μmol/L; p<0.05). In the HI-EC rats, the luminescence signal was observed at T+2 (mean [range]: 34,778 cpm [1617-2,918,810]), and was significantly decreased at T+6 (0 cpm [0-847,922]; p<0.05). Bacterial challenge was associated with a specific body weight loss and a decrease in gastrocnemius protein content, in alanine (AL 512±41 versus HI-EC 395±29 μmol/L; p<0.05), and in sulfur plasma amino acids. In conclusion, we propose a controlled model of HI with infectious complications characterized by specific metabolic alterations. Combined with the in vivo monitoring of the infection by bioluminescence, this model offers a valuable tool to evaluate specific strategies for HI patients.