Low Concentration of Wenyang Tonglin Decoction Promotes Conjugation and Transfer of Drug-Resistant Plasmids among Heterologous Strains.

Objective: To investigate the effect of low concentration of Wenyang Tonglin Decoction (WTD) on the binding conditions of R45 plasmid conjugative transfer under liquid phase conjugation and its mechanism.

Methods: Escherichia coli CP9 (R45) and Staphylococcus aureus RN450RF were cultured in medium containing WTD, and their minimum inhibitory concentration (MIC) values were obtained. Using promoter fusion technology, E. coli CP9 (R45) containing a promoter fusion was obtained. β-Galactosidase activity of TrfAp and TrbBp was tested, and the mRNA expression of regulatory factors (TrbA, KorA, and KorB) was detected by real-time fluorescent quantitative polymerase chain reaction.

Results: The MIC of E. coli CP9 (R45) was 400 g/L and that of S. aureus RN450RF was 200 g/L. When the drug concentration in the culture medium was 200 g/L, the highest number of conjugants was (3.47 ±0.20) × 10⁷ CFU/mL At 90 h of conjugation, the maximum number of conjugants was (1.15 ±0.06) × 10⁸ CFU/mL When the initial bacterial concentration was 10⁸ CFU/mL, the maximum number of conjugants was (3.47 ± 0.20) × 10⁷ CFU/mL. When the drug concentration was 200 g/L, the β-galactosidase activity of TrfAp and TrbBp significantly increased; the relative quantification of TrbA, KorA and KorB were significantly inhibited.

Conclusion: Low concentration of WTD promoted the development of bacterial resistance by affecting promoters and inhibiting the expression of regulatory factors.