The effect of Vancomycin and Gentamicin antibiotics on human osteoblast proliferation, metabolic function and bone mineralisation

Study Design. This study investigates the effect of Vancomycin and Gentamicin antibiotics on primary human osteoblasts. Osteoblasts were incubated with vancomycin, gentamicin or with Povidone-Iodine (PVI), at concentrations advocated for wound irrigation. Osteoblast proliferation, metabolic function and bone mineralisation were measured.

Objective. To model Gentamicin and Vancomycin wound irrigation in vitro and examine the effect on osteoblast viability and cellular function in comparison to 0.35% PVI.

Summary of Background Data. Vancomycin, Gentamicin and dilute PVI are employed as wound irrigants in spinal surgery to reduce infection. However, we have recently demonstrated that 0.35% PVI has a detrimental effect on osteoblast cellular function and bone mineralisation. Studies to determine the effects of antibiotic wound irrigation solutions on osteoblasts and bone mineralisation are therefore warranted.

Methods. Primary human osteoblasts were exposed for 20 min to either PBS control, Vancomycin (35 mM or 3.5 mM), Gentamicin (34 mM or 3.4 mM) or 0.35% PVI for 3 min. Cellular proliferation was measured over 7 days by MTS assay. Osteoblast metabolic function was determined using a Seahorse XFe24 Bioanalyzer. Mineralised bone nodules were quantified using Alizarin red.

Results. At concentrations advocated for wound irrigation, both Gentamicin (3.4 mM) and Vancomycin (3.5 mM) induced a transient 15-20% reduction in osteoblast proliferation, which returned to control values within 72 h. This was in marked contrast to the effect of 0.35% PVI which resulted in a sustained reduction in osteoblast proliferation of between 40-50% over 7 days. Neither Gentamicin nor Vancomycin at concentrations up to 10x clinical dose had any effect on osteoblast oxygen consumption rate, or significantly affected mineralised bone nodule formation.

Conclusion. Vancomycin and Gentamicin solutions, at concentrations advocated for intrawound application in spinal surgery have a small but transient effect on osteoblast proliferation, and no effect on either osteoblast metabolic function or bone nodule mineralisation.