Cordycepin affects Streptococcus mutans biofilm and interferes with its metabolism

Streptococcus mutans (S. mutans) contributes to caries. The biofilm formed by S. mutans exhibits greater resistance to drugs and host immune defenses than the planktonic form of the bacteria. The objective of this study was to evaluate the anti-biofilm effect of cordycepin from the perspective of metabolomics.BACKGROUNDStreptococcus mutans (S. mutans) contributes to caries. The biofilm formed by S. mutans exhibits greater resistance to drugs and host immune defenses than the planktonic form of the bacteria. The objective of this study was to evaluate the anti-biofilm effect of cordycepin from the perspective of metabolomics.The minimum inhibitory concentration (MIC) was determined to evaluate the antimicrobial effect of cordycepin on planktonic S. mutans. The 24-h biofilm was treated with 128 µg/mL of cordycepin for 10 min at the 8- or 20-h time points. Biofilm biomass and metabolism were assessed using crystal violet and MTT assays and cordycepin cytotoxicity was evaluated in human oral keratinocytes (HOK) using CCK-8 assays. The live bacterial rate and the biofilm volume were assessed by confocal laser scanning microscopy. Metabolic changes in the biofilm collected at different times during with cordycepin were analyzed by metabolomics and verified by quantitative real-time PCR.METHODSThe minimum inhibitory concentration (MIC) was determined to evaluate the antimicrobial effect of cordycepin on planktonic S. mutans. The 24-h biofilm was treated with 128 µg/mL of cordycepin for 10 min at the 8- or 20-h time points. Biofilm biomass and metabolism were assessed using crystal violet and MTT assays and cordycepin cytotoxicity was evaluated in human oral keratinocytes (HOK) using CCK-8 assays. The live bacterial rate and the biofilm volume were assessed by confocal laser scanning microscopy. Metabolic changes in the biofilm collected at different times during with cordycepin were analyzed by metabolomics and verified by quantitative real-time PCR.The results showed that treatment with 128 µg/mL cordycepin reduced both the biomass and metabolic activity of the biofilm without killing the bacteria, and cordycepin at this concentration showed good biocompatibility. Metabolomics analysis showed that differentially abundant metabolites following cordycepin treatment were mainly related to purine and nucleotide metabolism. After immediate treatment with cordycepin, genes related to purine and nucleotide metabolism were downregulated, and the levels of various metabo