In Vitro Antibacterial Effect Of Sodium Houttuyfonate Combined With Penicillin G On Methicillin-resistant Staphylococcus Aureus And Its Mechanism

Objective:To investigate the in vitro antibacterial effect of Sodium houttuyfonate combined with penicillin G on methicillin-resistant Staphylococcus aureus(MRSA).The expression of MRSA-related drug resistance genes mecA,mecR1 and blaR1 was detected to explore the mechanism of Sodium houttuyfonate reversing MRSA resistance.Methods:1.Twenty isolated and identified MRSA strains were collected from the microbiology laboratory of the Affiliated Hospital of North Sichuan Medical College,and the quality control strains were ATCC25923 standard strains stored in the microbiology laboratory of the Affiliated Hospital of North Sichuan Medical College.2.The drug sensitivity of MRSA clinical isolates was identified by k-B method.The minimum inhibitory concentration(MIC)of Sodium houttuyfonate and penicillin G alone on MRSA was detected by microbroth dilution method and AGAR dilution method.The MIC of Sodium houttuyfonate and penicillin G alone on MRSA was detected by checkerboard dilution method,and the fractional inhibitory concentration index(FICI)was calculated to judge the combined antibacterial effect of the drugs.The OD value of 96-well plate at wavelength 490nm was measured with a microplate reader,and the average inhibition rate of the drug on bacteria was calculated.3.PCR method was used to screen out 20 clinical strains of MRSA carrying related genes.MRSA strains were treated with Sodium houttuyfonate and penicillin G alone or in combination,respectively,and the expression of related drug resistance genes mecA,mecR1 and blaR1 were detected by RT-QPCR.Results:1.The MIC values of Sodium houttuyfonate and penicillin G alone were 60～80 μg/mL and 40～70U/mL by microbroth dilution method,respectively,with FICI=0.375～0.5625.14 strains showed synergistic effect and 6 strains showed additive effect.The MIC of Sodium houttuyfonate and penicillin G were 90～100μg/mL and 70～80 U/mL by AGAR dilution method,respectively.FICI of the two drugs combined were 0.375～0.625.12 strains showed synergistic effect and 8 strains showed additive effect.According to the measured OD value,the inhibition rate of Sodium houttuyfonate with 1/2MIC concentration and penicillin G with different concentrations was significantly higher than that of penicillin G alone(P<0.001).2.Rt-qPCR results showed that there was no significant difference in the expression of mecA,mecR1 and blaR1 genes before and after Sodium houttuyfonate and penicillin G alone or in combination(P>0.05).Conclusion:1.Sodium houttuyfonate has inhibitory effect on MRSA growth in vitro,and it can enhance the antibacterial effect of penicillin G,showing synergistic and additive effects.2.The expression of mecA,mecRl and blaR1 genes was not significantly affected by Sodium houttuyfonate.