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Antimicrob. Agents Chemother. doi:10.1128/AAC.00729-05
Copyright (c) 2006, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Influence on Mitochondria and Cytotoxicity of Different Antibiotics in High Concentrations on Primary Human Osteoblasts and Cell Lines

Department of Orthopedic Surgery, Cologne University Hospitals, Cologne, Germany; Institute for Medical Microbiology, Immunology, and Hygiene, Cologne University Hospitals, Cologne, Germany

^* To whom correspondence should be addressed. Email: Nicole.Duewelhenke{at}uk-koeln.de,

	Abstract

Osteomyelitis, osteitis, spondylodiscitis, septic arthritis and prosthetic-joint infections still represent the worst complications of orthopedic surgery and traumatology. Successful treatment requires, besides surgical débridement, long term systemic and high concentration local antibiotic therapy, with possible local antibiotic concentrations of 100 µg/ml and more. In this study we investigated the effect of 20 different antibiotics on primary human osteoblasts (PHO), the osteosarcoma cell line MG63 and the epithelial cell line HeLa. High concentrations of fluoroquinolones, macrolides, clindamycin, chloramphenicol, rifampin, tetracycline and linezolid during 48h of incubation inhibited proliferation and metabolic activity, whereas aminoglycosides and inhibitors of bacterial cell wall synthesis did not. IC₂₀ values for proliferation of PHO were determined as 20 - 40 µg/ml for macrolides, clindamycin, and rifampin, 60 - 80 µg/ml for chloramphenicol, tetracylin, and fluoroquinolones, and 240 µg/ml for linezolid. The proliferation of the cell lines was always less inhibited. We established the measurement of extracellular lactate concentration as an indicator of glycolysis using inhibitors of the respiratory chain (antimycin A, rotenone, sodium azide) and glycolysis (iodoacetic acid) as reference compounds, whereas inhibition of the respiratory chain increased and inhibition of glycolysis decreased lactate production. The measurement of extracellular lactate concentration revealed that fluoroquinolones, macrolides, clindamycin, rifampin, tetracycline and especially chloramphenicol and linezolid, impaired mitochondrial energetics in high concentrations. This explains partly the observed inhibition of metabolic activity and proliferation in our experiments. Because of differences in the energy metabolism, PHO provided a more sensitive model for orthopedic antibiotic usage than stable cell lines.

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