Antibiotic-induced release of endotoxin: in-vitro comparison of meropenem and other antibiotics

The influence of meropenem, a new carbapenem antibiotic, on cell morphology and in-vitro lipopolysaccharide (LPS) release from Escherichia coli was compared with that of imipenem, ceftazidime, tobramycin and ciprofloxacin. Free and cell-associated LPS was quantified by means of a capture ELISA method based on the recognition of E. coli LPS by monoclonal antibodies. Microscopically, meropenem was found to induce spheroplast formation similar to that seen with imipenem, while ceftazidime and ciprofloxacin induced filament formation. Free and cell-associated LPS levels were low in the presence of meropenem, imipenem, ciprofloxacin and tobramycin, but high in the presence of ceftazidime. Reduced endotoxin release appears to be a common property of carbapenem antibiotics. Morphological changes in bacteria in the presence of antibiotics do not predict their LPS-liberating effect since ciprofloxacin induced low levels of LPS despite causing filament formation.