The effects of tobramycin on MG63 cell viability and function

Management of bone infection and resulting bony defects is one of the major issues in Orthopaedic surgery. Systemic antibiotic therapy alone does not usually eradicate bacteria because of poor penetration into bone. Therefore, local application of aminoglycoside antibiotics at the site of infection can provide high drug concentrations to eradicate the bacteria. Aminoglycosides have been shown to be toxic to certain cells in the ears and in the kidneys. Approximately 5-10% of the people who are treated with aminoglycosides experience some side effect, affecting their hearing, sense of balance, or kidneys. Little information exists in the literature addressing the effects of the aminoglycoside, Tobramycin, on osteoblast cells. MG63 osteoblast-like cell line, were treated with varying concentrations of Tobramycin (0, 10, 50, 100microM) over a period of 24, 48 and 72 hours, harvesting them after each time period and performing assays to test their metabolic function (Glutathione assay) and cell membrane viability (MDA). The results show that Tobramycin at concentrations greater than the minimum inhibitory concentration (MIC) caused marked reductions in cell number with increased membrane damage as early as 48 hours. Glutathione levels within the cells were increased in the 50uM and 100uM treatments as early as 24 hours indicating impaired metabolic function. These results may have implications for using Tobramycin as antibacterial prophylaxis in Orthopaedic surgery, as its toxic effects may interfere with the osteoblasts ability to form bone, and delay healing.