The release of endotoxin from antibiotic-treated Escherichia coli and the production of tumour necrosis factor by human monocytes

Abstract

The influence of antibiotic-induced release of endotoxin from in-vitro grown Escherichia coli on the production of tumour necrosis factor-alpha (TNF) by human monocytes was studied. Antibiotics tested were: cefuroxime (7.5 and 75 mg/L); ceftazidime (10 and 100 mg/L); aztreonam (10 and 100 mg/L); imipenem (10 and 100 mg/L); and tobramycin (8 mg/L). The effect of the combination of cefuroxime plus tobramycin, and the effect of taurolidine, an endotoxin-binding agent, on TNF production was also tested. After incubation for 4 h, all antibiotic-treated cultures (high-dose) induced a similar rise in extracellular TNF production when compared to the controls. However, after incubation for 24 h, a significant rise in TNF production was noticed in the cefuroxime and aztreonam-treated cultures (6440 and 5969 ng/L, respectively) compared to the ceftazidime and imipenem-treated cultures (846 and 381 ng/L, respectively). The cefuroxime-induced release of TNF could be reduced by addition of tobramycin (from 6440 to 1615 ng/L). Similar differences in TNF production were noticed in cell-associated TNF. Dose-response curves did not demonstrate differences in TNF production in aztreonam or imipenem-treated cultures. However, for both cefuroxime and ceftazidime-treated cultures, low-dose treatment resulted in significantly higher production of TNF. The differences in TNF production between these antibiotics could be explained by the production of filaments following treatment with cefuroxime, aztreonam and low-dose ceftazidime, resulting in late bacterial lysis with high levels of endotoxin, whereas treatment with imipenem or high-dose ceftazidime resulted in the formation of spheroplasts, resulting in early lysis of the bacteria and much lower levels of endotoxin. The addition of taurolidine to either imipenem or aztreonam-treated cultures prevented a rise in TNF production as a result of nearly complete neutralization of the released endotoxin. It was concluded that the observed differences in TNF production by human monocytes in vitro were related to differences in the mechanisms and amount of antibiotic-induced release of endotoxin.

Clinical relevance of antibiotic-induced endotoxin release

“…No important differences in the capacity to cause endotoxin release were noticed between the antibiotics. As was seen in some in vitro studies, maximal bacterial lysis preceded a maximal increase in endotoxin levels by 1 (24,25). This decrease was also found when amikacin was added to ampicillin or cefotaxime monotherapy (9).…”

“…At 0.5 to 50 times the MIC, i.e., much lower concentrations than those used in the studies of Dofferhoff et al (24,25), ceftazidime released much more endotoxin than imipenem (44).…”

“…Treatment with ciprofloxacin gave intermediate levels of TNF release (70). In a comparable study, cefuroxime, low-dose ceftazidime, and aztreonam induced greater production of extracellular TNF than high-dose ceftazidime, imipenem, or tobramycin (24). High concentrations of cephalosporins resulted in less TNF production than low concentrations (24).…”

“…In a comparable study, cefuroxime, low-dose ceftazidime, and aztreonam induced greater production of extracellular TNF than high-dose ceftazidime, imipenem, or tobramycin (24). High concentrations of cephalosporins resulted in less TNF production than low concentrations (24). TNF production by human whole blood ex vivo was measured during antibiotic killing of H. influenzae type b (5).…”

Comparable Endotoxic Properties of Lipopolysaccharides Are Manifest in Diverse Clinical Isolates of Gram-Negative Bacteria

“…More recently, correlative data from in vitro, ex vivo, and in vivo studies using viable intact gram-negative microorganisms all provide strong indications that the production of cytokines depends, to at least some extent, on the degree to which various antibiotics induce the release of LPS from gram-negative bacteria (3,5,6,15,29). Furthermore, the amount of LPS released is now recognized to depend, at least in part, on the differential binding of various ␤-lactam antibiotics to selective penicillin-binding proteins (3,15).…”