An Experimental Study on the Addition of Bacteria to Residual Anticancer Drugs: Evaluation of the Effect on Bacterial Growth

Abstract

Using anticancer drugs as an example, we examined the possibility of reusing residual drugs. The use of residual drugs is not widespread because of concerns regarding bacterial contamination. We mixed anticancer drugs with bacteria and investigated their effects on bacterial growth. The anticancer drugs carboplatin, paclitaxel, etoposide, irinotecan, methotrexate, and 5-fluorouracil (5-FU) were mixed with Staphylococcus aureus, Enterococcus faecalis, Serratia marcescens, and Escherichia coli. After a certain period, the number of bacteria was counted. Irinotecan showed no antibacterial activity, whereas 5-FU showed high antibacterial activity against the bacteria tested. The 5-FU also showed a minimum inhibitory concentration value in the range of 8-80 μg/mL, depending on the bacterial species. The 5-FU dose-dependently inhibited S. aureus growth at more than 0.8 µg/mL. Since protein synthesis systems are reportedly antibiotic targets, we used a cell-free protein synthesis system to confirm the mechanism of the anticancer agent's antibacterial activity. The 5-FU and methotrexate had direct inhibitory effects on protein synthesis. It is suggested that even if the residual drugs are contaminated with bacteria, there will be no microbial growth or microbes will be killed by the drug. With careful monitoring, the 5-FU could potentially be used for antimicrobial purposes.