The comparison of susceptibility to endogenous Pseudomonas aeruginosa septicemia between endotoxin responder and non-responder mice

Abstract

Pseudomonas free specific pathogen free (SPF) mice were orally inoculated with Pseudomonas aeruginosa D-4m strain via drinking a 0.45% NaCl solution containing P.aeruginosa. The animals also received ampicillin (ABPC) to promote indigenous colonization. The Pseudomonas colonized mice, rendered neutropenic by cyclophosphamide injection, developed fatal P.aeruginosa bacteremia. Using this model, a comparison of mortality due to P. aeruginosa endogenous septicemia was made between C3H/HeN (endotoxin-sensitive) and C3H/HeJ (endotoxin-resistant) mice. C3H/HeJ mice were hypersusceptible to P. aeruginosa endogenous septicemia, while C3H/HeN mice were resistant. P. aeruginosa levels in the livers were high enough to cause death in C3H/HeJ mice, while the bacteria were eliminated from the livers of C3H/HeN mice. When both strains of mice were also inoculated with P. aeruginosa intravenously, the 50% lethal doses (LD₅₀) of P. aeruginosa D-4m strain were 10^2.4 and 10^2.8 CFU/mouse in C3H/HeJ and C3H/HeN mice, respectively. The clearance rate of P. aeruginosa from blood was similar in the two groups of mice. These results suggest an important difference between endotoxin-sensitive and -resistant mice in endogenous infection.