The Study On Combined Antimicrobials Test Agaisnt Methicillin-resistant Staphylococcus Aureus(MRSA) And The Mutagenesised Strains In Vitro

Purpose:Methicillinresistantstaphylococcus aureus(MRSA)often leads to the community infection and the hospital infection.At the same time,it is acritical pathogenic bacteria causing human disease.MRSA is called the super bacteria,which has a strong ability to adapt to the environment and the complexity of the mechanism of drug resistance.Besides,it is highly resistant to most antibacterial agents.Strains that have decreased sensitivity to vancomycin which is known as the last line of defense for the treatment of MRSA infection have appeared,which brings serious challenges to clinical treatment.The selective pressure of antibiotics on bacteria is an important factor for the generation of drug-resistant bacteria.There are several heterogeneous vancomycin mediated drug resistance abroad,which are hVISA and VISA,even VRSA.A crucial factor for the resistance of Staphylococcus aureus to vancomycin is the cumulative mutation of the gene under the selective pressure of antibiotics,and which can gradually develops into a vancomycin insensitive strain.It is of great significance to explore a treatment plan that reduces the sensitivity of vancomycin.In this study,the MIC values of vancomycin,ceftazidime,ceftriaxone were tested.,and vancomycin were combined with ceftazidime and ceftriaxone to determine the FIC index of in vitro susceptibility testing.The combined effect of the application of clinical MRSA infection to provide new ideas.Method:1.Strains collection: The 21 isolations of MRSA from blood infection of hospitalized patients who suffered from blood flow infection in the first hospital affiliated of China Medical University in 2013-2016 was selected.2.Drug sensitivity test: the broth microdilution method was used to detect the MICvalue of vancomycin,Ceftriaxone and ceftazidime.The chessboard was used to detect the effect of combined use of vancomycin with ceftriaxone and ceftazidime.3.It induced two strains of MRSA strains through the use of vancomycin monotherapy,vancomycin and ceftriaxone,vancomycin combined with piperacillin / tazobactam and observed the effects of several schemes on the changes of vancomycin MIC value for a long time.4.The effect of combined use of ceftriaxone and ceftazidime with vancomycin were detected by chessboard design of minim broth.Result:1.Ceftriaxone combined with vancomycin effect: vancomycin combined with ceftriaxone had mostly no Synergieseffect onMRSA strains of the low MIC value.,Only a few strains have an additive effect.2.ceftazidime combined with vancomycin effect: vancomycin combined with ceftazole had mostly no Synergieseffect onMRSA strains of the low MIC value.,Only a few strains have an additive effect.3.The MIC value changeof MRSA strainsamong the antibiotic exposure environment in vitro: among vancomycin exposure environment,the MIC value of MRSA strains were induced to increase.vancomycin combined with ceftriaxone vancomycin combined with Piperacillin/tazobactam had a preventive effect of preventing increased vancomycin MIC value increase.4.The Combined use of vancomycin combined with ceftriaxone agaisnt the MRSA strains which mutagenesised: vancomycin combined with ceftriaxone showed synergistic effect and additive effect on MIC=2?g /m L and MIC=4?g /m L respectively.5.The Combined use of vancomycin combined with ceftazidime agaisnt the MRSA strains which mutagenesised: Vancomycin comined with ceftazidime on MIC=2?g /mL strain MRSA showed an additive effect.Conclusion:1.There is no antagonism between vancomycin and ceftriaxone,vancomycin and ceftazidime in vitro combined susceptibility testing,mainly irrelevant effects,and individual strains are additive or synergistic.2.In the environment of vancomycin in vitro,vancomycin can induce the elevation of vancomycin MIC of MRSA strains.Vancomycin combined with ceftriaxone,vancomycin combined with piperacillin/tazobactam can effectively delay the increase of vancomycin MIC value of MRSA.3.With the increase of MIC value of MRSA vancomycin,the effects of vancomycin and ceftriaxone,vancomycin and ceftazidime combined drug sensitivity test are different:As the MIC of vancomycin increases,the results of the combined drug susceptibility test change from irrelevant to additive or synergistic effects.