BIOLOGICAL CHARACTERIZATION OF ENDOTOXINS RELEASED FROM ANTIBIOTIC-TREATED PSEUDOMONAS-AERUGINOSA AND ESCHERICHIA-COLI

The supernatants taken from Pseudomonas aeruginosa and Escherichia col i cultures in human sera or chemically defined M9 medium in the presen ce of ceftazidime (CAZ) contained high levels of endotoxin, while thos e taken from the same cultures in the presence of imipenem (IPM) yield ed a very low level of endotoxin. The biological activities of endotox in in the supernatants were compared with those of phenol water-extrac ted lipopolysaccharide (LPS), The endotoxin released from the organism s as a result of CAZ treatment (CAZ-released endotoxin) contained a la rge amount of protein. The protein, however, lacked endotoxic activity , since the endotoxin did not show any in vivo toxic effects in LPS-hy poresponsive C3H/HeJ mice sensitized with D-(+)-galactosamine (GalN) o r any activation of C3H/HeJ mouse macrophages in vitro. The activities of CAZ- and IPM-released endotoxin (as assessed by a chromogenic Limu lus test) were fundamentally the same as those of P. aeruginosa LPS, s ince their regression lines were parallel. The CAZ-released endotoxin was similar to purified LPS with respect to the following biological a ctivities in LPS-responsive C3H/HeN mice and LPS-hyporesponsive C3H/He J mice: lethal toxicity in GalN-sensitized mice, in vitro induction of tumor necrosis factor-and NO production by macrophages, and mitogen-a ctivated protein kinase activation in macrophages. The macrophage acti vation by CAZ-released endotoxin as well as LPS was mainly dependent o n the presence of serum factor and CD14 antigen. Polymyxin B blocked t he activity. These findings indicate that the endotoxic activity of CA Z-released endotoxin is due primarily to LPS (lipid A).