A preliminary study of age-related difference in resistance to sepsis in the rat model.

Although the pathophysiology of intraabdominal sepsis is well established in the adult animal, there is a paucity of similar information in the newborn animal. Using the Wichterman (K.A. Wichterman, A.E. Baue, and I.H. Chaudry, Journal of Surgical Research 29: 189, 1980) model of intraabdominal sepsis, 42 Sprague-Dawley suckling rat pups and 42 adults underwent cecal ligation followed by a single needle puncture of the cecum. Whereas a mortality of 47.6% was noted in the adult animals, only 7.1% of the suckling animals succumbed by the end of 1 week. After the ip LD50 of Escherichia coli was determined independently in each age group, appropriate doses of the bacteria were injected into the peritoneums of 36 suckling and 30 adult rats. The peritoneal fluid was aspirated at 0, 2, 4, 8, 24, and 48 hr and the bacterial concentration in the suspension was determined. The rate of bacterial clearance from the peritoneum of the suckling rats was found to be significantly greater at 2, 4, and 8 hr as compared with the adult animal. In vitro assay of the phagocytic activity of the peritoneal macrophages demonstrated a significantly higher activity in the cells obtained from the suckling rats than in those from the adult (P less than 0.05). A more efficient bacterial clearance and a higher phagocytic activity in the peritoneal macrophages of the suckling rats may contribute to the difference in the mortality between the two age groups.