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 (cefazolin, 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 cells cultured from the human anulus after they were exposed to four antibiotics. Summary of Background Data. Previous studies concerning the effect of antibiotics on the disc have used animal models or explanted discs, but little is understood about the effect of antibiotics on the proliferation, viability, 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 grown in monolayer culture. The latter measurement used a cytosensor microphysiometer to monitor the rate at which cells acidified their microenvironment, an event that is proportional to cellular metabolism because it reflects the excretion over time of acidic products such as lactic acid from glycolysis and CO, from cellular respiration. Results. After 48 hours of antibiotic exposure, cell viability was significantly lower as a result of all four antibiotics at the highest concentration tested. Cell proliferation was lower after exposure to cefazolin and cefamandole, During a B-hour antibiotic exposure, anulus cells in the highest concentration of cefamandole or vancomycin displayed a significantly decreased rate of cell metabolism. Conclusions. These findings show that high doses of antibiotics can have direct, deleterious effects on cultured disc cell survival, cell proliferation, and metabolic rates. Discitis is a serious primary or postoperative complication that often requires prolonged antibiotic treatment. Studies such as the current investigation with cultured cells from the anulus show the importance of a greater understanding concerning antibiotic effects on disc cell proliferation and metabolism.