Effect of Bacterial Media on the Evaluation of the Antibacterial Activity of a Biomaterial Containing Inorganic Antibacterial Reagents or Antibiotics

Several studies have been performed to assess the effectivesness of the antibacterial coating of a biomaterial to reduce surgical site infection. However, evaluations of these materials are inconsistent, and therefore it is difficult to compare their antibacterial performance. In this study, we evaluated the influence of different media such as nutrient broth (NB), Mueller-Hinton broth (MHB) and fetal bovine serum (FBS) on the antibacterial activity of AgNO3- or gentamicin-added bone cement using a modified ISO 22196 standard to devise a method to evaluate the antibacterial activity of biomaterials in vitro. The antibacterial activity results against Staphylococcus aureus and Escherichia coli were different in each medium. The antibacterial activity of AgNO3 in FBS was lower than the other media, whereas the antibacterial activity of gentamicin in FBS was higher than in the other media. It was assumed that the fluctuating antibacterial activity was influenced by serum components. The results showed that the ISO 22196 antibacterial evaluation method is suitable to evaluate antibacterial biomaterials after modifying the medium to FBS.