Effects of Sophora alopecuroides L. extract on AcrAB-TolC pump inhibition in E. coli

Gram-negative multi-drug resistant bacteria cause untreatable infections. Efflux pumps have a key role in generation of multi-drug resistant bacteria. The inhibition of this pump is a strategy against drug resistance. The aim of this research was to study the effect of Sophorea alopecuroides L. extract on inhibition of AcrAB-TolC pump in E. coli mutants. The extract containing total alkaloids, was used to measure minimum inhibitory concentration (MIC) of extract alone and in combination with ciprofloxacin. Resistant mutants were pretreated with a concentration lower than MIC for different time periods and then MIC was measured for ciprofloxacin. The expression of acrA in mutants treated or untreated with the extract in present and absent of ciprofloxacin was assayed. Results showed that the extract had antibacterial activity by itself and in a concentration lower than MIC in combination with ciprofloxacin had synergistic effect. Meanwhile, a 36-hour pretreatment caused decrease in MIC of ciprofloxacin. Results of real time PCR showed that treatment with extract led to decrease in acrA expression. In conclusion, the extract of Sophorea alopecuroides in E. coli multi drug resistant mutants possibly acts as a pump inhibitor. Therefore, better isolation of plant alkaloids and study their effects could provide a strategy for the synthesis of new drug.