| The continuous spread and growth of bacterial resistance has evolved into a major public health problem worldwide.Methicillin-resistant Staphylococcus aureus(MRSA)is an important pathogen causing nosocomial infections and veterinary clinical infections due to its multiple drug resistance,It is highly infectious and difficult to control.Diseases such as sepsis,pneumonia or cow mastitis caused by infection have caused serious trauma to the animal husbandry industry and caused public health problems to the society.Some of the active ingredients of traditional Chinese medicine have the characteristics of high safety,resistance to drug resistance,and strong antibacterial activity.They have been explored by researchers as inhibitors of drug-resistant bacteria.The antibacterial effect of flavonoids in Chinese herbal medicines is particularly outstanding and the antibacterial spectrum is broad.Therefore,this study intends to screen out 78 kinds of flavonoids of Chinese medicine monomers that can enhance the sensitivity of Staphylococcus aureus resistant strains to ceftiofur sodium.To investigate its antibacterial effect in the body and preliminary study its synergistic antibacterial mechanism,to provide safe,reliable and effective new drugs for the treatment of S.aureus infectious diseases in veterinary clinics.In this study,78 kinds of flavonoids of Chinese medicine monomers were screened by the checkerboard method of drug susceptibility experiments to screen out proanthocyanidins that are synergistic with ceftiofur sodium against resistant Staphylococcus aureus,that is,25 μg/mL proanthocyanidins can make ceftiofur sodium against MRSA standards The minimum inhibitory concentration(MIC)of strain ATCC33591 was reduced from 32 μg/mL to 4 μg/mL,and the combined inhibitory index(FICI)was 0.375,showing a synergistic antibacterial effect.That is,the combined application of ceftiofur sodium and proanthocyanidin reversed the effect of ATCC33591 on cephalosporin.The drug resistance of Thiofu,the combination of the two also shows a synergistic antibacterial effect on clinical strains of MRSA(8 out of 10 strains),and the FICI is 0.3125 ～ 0.5.The minimum bactericidal concentration(MBC)determination showed that 12.5 μg/mL proanthocyanidin can reduce the MBC value of ceftiofur sodium against ATCC33591 from 64 μg/mL to 16 μg/mL;the growth curve measurement shows that 100 μg/mL proanthocyanidin has a significant effect on the growth of ATCC33591 Inhibition;Proanthocyanidins can enhance the antibacterial post-bacterial effect(PAE)of ceftiofur sodium and extend the PAE against ATCC33591 from 1.3 h to 3.5 h.The CCK-8 assay is used to detect the toxicity of proanthocyanidins to porcine testicular cells(ST).The results showe that proanthocyanidins have no effect on cell viability and have no cytotoxicity.Furthermore,the thigh muscle model of mice infected against ATCC 33591 is established,and the survival rate and bacterial colonization rate are taken as indexes.It is observed that the combination of proanthocyanidin and ceftiofur sodium has significant therapeutic effect on mice,which is better than single drug treatment.In this article,the synergistic antibacterial mechanism of proanthocyanidin and ceftiofur sodium is initially explored.The effect of proanthocyanidin on cephalosporinase activity was determined,and the results showed that proanthocyanidin can protect ceftiofur sodium by inhibiting cephalosporinase activity.Through scanning electron microscopy,it can be seen that proanthocyanidins can destroy the integrity of bacterial cell membranes,showing antibacterial activity against Staphylococcus aureus.In summary,the combined application of proanthocyanidins and ceftiofur sodium obtained by the screening has a synergistic antibacterial effect on drug-resistant Staphylococcus aureus both in vivo and in vitro,providing a new idea for the research and development of inhibitors of drug-resistant bacteria,as well as traditional Chinese medicine.The development of antibacterial agents combined with western medicine provides basic data and theoretical support. |
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