Fig. 6

Pingwei Pill potentiated the activity of colistin in Salmonella sp. strain HYM2 cell membrane injury without inducing drug resistance. Following treatment with sub-MICs of colistin, Pingwei Pill or combination therapy, the morphological changes and viability of Salmonella sp. strain HYM2 were visualized using SEM (A–D) and a LIVE/DEAD BacLight Bacterial Viability Kit (E–H). A, E Bacteria without treatment. B, F Bacteria treated with sub-MICs of colistin (2 μg/mL). C, G Bacteria treated with Pingwei Pill (1.024 mg/mL). D, H Bacteria treated with the combination of colistin (2 μg/mL) and Pingwei Pill (1.024 mg/mL). The resistance development of various bacterial strains by serial passaging with the indicated treatment. I K. pneumoniae ZJ02 without any treatment as control, colistin (sub-MIC16μg/mL), Pingwei Pill (1.024 mg/mL), Pingwei Pill (1.024 mg/mL) plus colistin (0.5 μg/mL); J Salmonella sp. strain HYM2 without any treatment as control, colistin (sub-MIC 4 μg/mL), Pingwei Pill (1.024 mg/mL), Pingwei Pill (1.024 mg/mL) plus colistin (0.25 μg/mL); K E. coli ZJ478 without any treatment as control, colistin (sub-MIC 4 μg/mL), Pingwei Pill (1.024 mg/mL), Pingwei Pill (1.024 mg/mL) plus colistin (0.5 μg/mL); L E. coli DH5α (pUC19-mcr-1 without any treatment as control, colistin (sub-MIC 2 μg/mL), Pingwei Pill (1.024 mg/mL), Pingwei Pill (1.024 mg/mL) plus colistin (0.5 μg/mL); The y axis indicates the MIC measured directly from the tubes during the serial passages (mg/L), and the x axis is the number of passages. Colistin used as comparison was indicated. **P < 0.01