Pseudomonas aeruginosa Compared with Escherichia coli Produces Less Endotoxemia: Results (4)

Pseudomonas aeruginosa Compared with Escherichia coli Produces Less Endotoxemia: Results (4)Pseudomonas aeruginosa-infected dogs had markedly lower endotoxin levels compared with the E coli groups (p<0.0001). Eleven of 32 animals died in the P aeruginosa group compared with none of the nonirradiated E coli dogs (7 and 14 x 109 CFU/kg), despite circulating endotoxin concentrations that were more than tenfold lower in the P aeruginosa-infected dogs (Table 2). Other parameters (Table 3) also pointed to a pattern of greater severity of illness in the setting of relatively low levels of endotoxemia in P aeruginosa vs E coli groups. As shown, P aeruginosa (14 X 109 CFU/ kg) produced greater falls in MAP and LVEF (p<0.05) than E coli (7 X109 CFU/kg), despite the higher endotoxin concentrations produced by the latter.
This disparity between endotoxin concentrations and clinical end points in the P aeruginosa group could not be explained by additive toxicity from exotoxin A, a potent toxin thought to be important in Pseudomonas infections. The P aeruginosa strain used in these experiments released no detectable exotoxin A as measured by Western blot after overnight growth in high-yield media (Fig 4). Further, the endotoxin content per bacterium, as determined by LAL assay, was similar for the E coli and P aeruginosa used in this study, 25.5 fg/CFU and 26.6 fg/CFU, respectively (in equivalent weight of US standard endotoxin). buy ortho tri-cyclen online
As stated above, radiation-induced leukopenia increased mortality from 0 to 60 percent in E coli-infected dogs, but it did not affect the pattern or severity of the hemodynamic abnormalities (Fig 2 and 3, and Table 3). The increased mortality seen in irradiated, E coZt-infected dogs was not caused by higher concentrations of circulating endotoxin (Table 2), despite the marked immune suppression.

Table 3—Mean Decreases in Mean Arterial Pressure and Left Ventricular Ejection Fraction

Study Group Decrease in MAP, mm Hg Decrease in LVEF
1. Ecoli
7X10° — 24 ±6 — 0.16±0.03
14X10* — 30 ±5 -0.27 ±0.03
14 x 10” (with radiation) — 32 ±4 -0.25 ±0.02
2. P aeruginosa^ — 41 ±3 -0.24 ±0.02


Figure 4. Western blot of supernatants from P aeruginosa stained for exotoxin A. P aeruginosa strain PA103, a known exotoxin A producer, is shown in lane 1. The dark band at a MW of approximately 71,000 represents intact monomeric exotoxin A (see purified exotoxin A standard in lane 4). Bands above and below this point represent exotoxin A aggregates and partially digested exotoxin A, respectively. Concentrated supernatant from the P aeruginosa strain used in this study was run in lanes 2 and 3. No exotoxin A was detected.

Category: Pseudomonas aeruginosa

Tags: aeruginosa, endotoxin, sepsis, septic shock