A rat model of septic shock using live Escherichia coli and response to Noradrenaline

Popular animal models of septic shock involve injections of endotoxin (bacterial lipopolysaccharide). Other methods that induce sepsis are often time-consuming and require long-term monitoring facilities. Further, individual models using different bacterial strains can deepen our understanding of sepsis pathophysiology. Hence, our objective was to develop an acute and functional Wistar rat model of septic shock using live strains of Escherichia coli and then administer Noradrenaline, a known sympathomimetic drug, to study if the response is along expected lines. After random allocation to one of three groups (Group 1 – E. coli alone, n=7; Group 2 – E. coli followed by Noradrenaline, n = 7 and Group 3 – control (n = 4), which received saline injections), Wistar rats were anesthetised and intra-arterial pressure was recorded from carotid artery catheter. Live E. coli suspended in normal saline (5 Mcfarland concentration; dose – 650 uL/100 g body weight) was injected through the tail vein to induce sepsis. When mean arterial pressure dropped to 50% of its value before E. coli injection, Noradrenaline was injected in Group 2. The average time (t1, n = 14) for the septic shock to set in was about 1.94 ± 0.97 h. Six out of seven rats (Group 1) died within 60 min without intervention. The addition of Noradrenaline after hypotension in Group 2 prolonged the time to death significantly by about 170 min. The rat septic shock model using E. coli described in the study is an acute, stable, and functional model to study various aspects of septic shock. Administration of Noradrenaline prolonged the animal’s life in septic shock as expected. Future studies using other common sepsis agents encountered in clinics can be undertaken similarly.