Effect of antibiotic class and concentration on the release of lipopolysaccharide from Escherichia coli.
The ability of six antibiotics from different classes to release radiolabeled lipopolysaccharide (LPS) from a phenotypically smooth galE mutant of Escherichia coli O111:B4 was examined. Antibiotic concentrations were 0.0625-512 micrograms/mL. LPS release increased as a function of the antibiotic concentration, reaching a limit at or near the concentration that killed the majority of bacteria. The maximum amount of LPS released by polymyxin B was 40.6% +/- 0.9%, by gentamicin 58.2% +/- 2.5%, by ciprofloxacin 65.8% +/- 2.5%, by ceftazidime 73.1% +/- 0.9%, by tetracycline 75.3% +/- 10.0%, and by imipenem 79.7% +/- 2.3%. In timed experiments, ceftazidime released 61.9% +/- 1.2%, imipenem 51.1% +/- 8.8%, and tetracycline 39.7% +/- 4.4% of the LPS within the first hour of incubation, whereas polymyxin B released 13.5% +/- 1.9%, gentamicin 9.8% +/- 3.6%, and ciprofloxacin 12.7% +/- 2.6% of the LPS (P < .05). Fluoro-radiography and immunoblot analyses revealed similar migration patterns for antibiotic-released and cell-bound LPS on SDS-PAGE gels, suggesting similar O-polysaccharide content in the two LPS fractions. The amount and rate of LPS release from an E. coli strain was dependent upon antibiotic class and concentration.
Department of Medicine, Uniformed Services University of the Health Sciences, F. Edward Hébert School of Medicine, Bethesda, MD 20814-4799.
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Evans
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Pollack
D000900:Anti-Bacterial Agents / Q000145:classification / Q000494:pharmacology*; D002442:Ceftazidime / Q000494:pharmacology; D002939:Ciprofloxacin / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D005839:Gentamicins / Q000494:pharmacology; D015378:Imipenem / Q000494:pharmacology; D015151:Immunoblotting; D008070:Lipopolysaccharides / Q000378:metabolism*; D011112:Polymyxin B / Q000494:pharmacology; D013752:Tetracycline / Q000494:pharmacology
D000900:Anti-Bacterial Agents; D005839:Gentamicins; D008070:Lipopolysaccharides; D002939:Ciprofloxacin; D015378:Imipenem; D002442:Ceftazidime; D013752:Tetracycline; D011112:Polymyxin B