Effects of very high antibiotic concentrations on human intervertebral disc cell proliferation, viability, and metabolism in vitro

Study Design. Four antibiotics commonly used during spinal surgery (cefazol in, gentamycin, cefamandole, and vancomycin) were tested for their effects on cultured human disc cells from the anulus. Objective. To determine the viability, proliferation, and metabolism of cel ls cultured from the human anulus after they were exposed to four antibioti cs. Summary of Background Data. Previous studies concerning the effect of antib iotics on the disc have used animal models or explanted discs, but little i s understood about the effect of antibiotics on the proliferation, viabilit y, and metabolism of cells from the anulus. Methods. In this study, H-3-thymidine incorporation, trypan blue exclusion, and cell metabolism were determined using cells from the human anulus grow n in monolayer culture. The latter measurement used a cytosensor microphysi ometer to monitor the rate at which cells acidified their microenvironment, an event that is proportional to cellular metabolism because it reflects t he excretion over time of acidic products such as lactic acid from glycolys is and CO, from cellular respiration. Results. After 48 hours of antibiotic exposure, cell viability was signific antly lower as a result of all four antibiotics at the highest concentratio n tested. Cell proliferation was lower after exposure to cefazolin and cefa mandole, During a B-hour antibiotic exposure, anulus cells in the highest c oncentration of cefamandole or vancomycin displayed a significantly decreas ed rate of cell metabolism. Conclusions. These findings show that high doses of antibiotics can have di rect, deleterious effects on cultured disc cell survival, cell proliferatio n, and metabolic rates. Discitis is a serious primary or postoperative comp lication that often requires prolonged antibiotic treatment. Studies such a s the current investigation with cultured cells from the anulus show the im portance of a greater understanding concerning antibiotic effects on disc c ell proliferation and metabolism.