Total alkaloids of Sophora alopecuroides- and matrine-induced reactive oxygen species impair biofilm formation of Staphylococcus epidermidis and increase bacterial susceptibility to ciprofloxacin

OBJECTIVE: To investigate the mechanism by which total alkaloids of Sophora alopecuroides (TASA) and matrine (MT) impair biofilm to increase the susceptibility of Staphylococcus epidermidis (S. epidermidis) to ciprofloxacin. METHODS: The minimum biofilm inhibitory concentration (mBIC) was determined using a 2-fold dilution method. Structure of biofilm of S. epidermidis was examined by Confocal Laser Scanning Microscope (CLSM). The cellular reactive oxygen species (ROS) was determined using a DCFH-DA assay. The key factors related to the regulation of ROS were accessed using respective kits. RESULTS: TASA and MT were more beneficial to impair biofilm of S. epidermidis than ciprofloxacin (CIP) (P < 0.05). TASA and MT were not easily developed resistance to biofilm-producing S. epidermidis. The mBIC of CIP decreased by 2–6-fold following the treatment of sub-biofilm inhibitory concentration (sub-BIC) TASA and MT, whereas the mBIC of CIP increased by 2-fold following a treatment of sub-BIC CIP from the first to sixth generations. TASA and MT can improve the production of ROS in biofilm-producing S. epidermidis. The ROS content was decreased 23%−33% following the treatment of sub-mBIC CIP, whereas ROS content increased 7%−24% following treatment with TASA + CIP and MT + CIP combination from the first to sixth generations. Nitric oxide (NO) as a ROS, which was consistent with the previously confirmed relationship between ROS and drug resistance. Related regulatory factors-superoxide dismutase (SOD) and glutathione peroxidase (GSH) could synergistically maintain the redox balance in vivo. CONCLUSION: TASA and MT enhanced reactive oxygen species to restore the susceptibility of S. epidermidis to ciprofloxacin.