Effect of Thickening Agents on the In Vitro Antibacterial Activity of Vancomycin Hydrochloride Powder

When vancomycin hydrochloride (VCM) powder mixes with xanthan gum-based thickening agents in food, lumps or other property-related changes may occur. Previous studies have reported delayed disintegration and elution of the drug and its adsorption on to xanthan gum, which is the main ingredient of thickened food products. If the addition of thickening agents can affect the antimicrobial activity of VCM powder as previously reported, it might interfere with the treatment of Clostridioides difficile infection (CDI). In this study, we investigated the effect of the addition of xanthan gum-based thickening agents on the antibacterial activity of VCM against Clostridioides difficile in vitro. The VCM concentration at 0 min after adding 3% Tsururinko Quickly (Clinico, Tokyo) to VCM powders (Shionogi, Osaka and Meiji Seika Pharma, Tokyo) was lower than that of the control [Shionogi: 65.15±35.57%, Meiji Seika Pharma: 77.00±15.81% (mean±standard deviation), ** p<0.01, Dunnet's test]. However, the VCM concentration at 30 min after the addition recovered to the control level. The drug susceptibility tests for C. difficile and Staphylococcus aureus using the disk diffusion method showed no effect of addition of 3% Tsururinko Quickly. Our in vitro evaluations showed that the addition of xanthan gum-based thickeners to VCM powders had a negligible effect on the treatment of CDI.