Preliminary Study On The Sensitivity Of Enterococcus Faecium To New Macrolide Drugs Solithromycin And New Psoralen Isoflavones

【Objects】1.To evaluate the in vitro antimicrobial activity of new class of macrolide Solithromycin as well as the association between the antibiotic susceptibility and the presence of resistance genes(erm A,erm B and erm C)in Enterococcus faecium isolates collected in our hospital.2.To investigate the antimicrobial activity of Neobavaisoflavone against clinical Enterococcus faecium isolates preliminarily.【Method】1.Source of Clinical Bacterial Strains: A total of 122 non-duplicate Enterococcus faeciumisolates were collectedfrom different inpatients at Huazhong University of Science and Technology Union Shenzhen Hospitalfrom 2011 to 2017.The isolates were identified by standard methods using the BD PHOENIX automated microbiology system and mass spectrometry system.2.Measurement of MIC value by agar dilution method:Antimicrobial susceptibility of the Enterococcus faecium isolates to erythromycin and Solithromycin was evaluated by the agar dilution method according to Clinical and Laboratory Standards Institute guidelines.3.Detection of drug-resistant genes: Resuscitate the stored clinical Enterococcus faecium isolates and increase the bacteria by culturing.After 12-16 hours,the genomic DNA of the strains were extracted with DNA extraction reagents according to the operating method of the instructions.The presence of resistance genes in Enterococcus faecium isolates including erm A,erm B and erm C were investigated by PCR and sequence alignment.4.Measurement of MIC value by broth dilution method:MICs of azithromycin 、Solithromycin、linezolid、vancomycin、and Neobavaisoflavone for seven selected clinical strains were determined by the broth dilution method.5.Study of the synergistic effect of Neobavaisoflavone combined with other antibiotics against Enterococcus faecium: The combined antibacterial effect of Neobavaisoflavone with other antibiotics were characterized by growth curves in response to combinations of corresponding drugs.【Result】1.The data of our experiments indicated that 104(85.2%)of the 122 clinical Enterococcus faecium isolates were not susceptible to erythromycin,while 69(56.6%)of the isolates showed an MIC value of 4μg/ml for Solithromycin.2.The carrying rate of resistance genes erm A、B、C were 9.8%、32.7%、45.9% respectively;and 56.6%(64/94)of erm(+)Enterococcus faecium showed an MIC value of 4μg/ml for Solithromycin.3.The MIC values of Neobavaisoflavone were not below 50μmol/ml.The growth curve analysis indicated that Neobavaisoflavone have acceptable antibacterial activities against Enterococcus faecium at the concentration of 1/2 MIC.The Neobavaisoflavone had a preliminary synergy with Solithromycin and linezolid.【Conclusion】1.The overall MICs of Solithromycin against clinical Enterococcus faecium isolates were not above 4μg/ml,the antibacterial activity of Solithromycin is stronger than erythromycin.whether Solithromycin can overcome the erm resistance mechanism in Enterococcus faecium need to be further researched.2.Neobavaisoflavone exhibited preliminary inhibitory activities against Enterococcus faecium.The Neobavaisoflavone had a preliminary synergistic effect combined with Solithromycin and linezolid,which may enhance the antibacterial activity of these antibacterial drugs,but there is no obvious synergistic effect when combined with vancomycin.The antibacterial mechanism of Neobavaisoflavone need to be further researched.