Screening Of Effective Drug Combination Against Carbapenem-resistant Acinetobacter Baumannii

ObjectiveTo study the antibacterial effect of the two-drug combination against six strains of Acinetobacter baumannii from the “Laboratory diagnosis,clinical management and infection control of the infections caused by extensively drug-resistant Gram-negative bacilli: a Chinese consensus statement” in 2016.And to compare the antibacterial effects of the program to provide a basis for clinical treatment.It was then determined whether the combination of the non-antibacterial agent ambroxol hydrochloride or amlodipine with the antibacterial agents had the effect of anti-Acinetobacter baumannii and the effect of antibiofilm.MethodsWe studied the following regimens of two drug combination against 6 AB strains(1)recommended in the consensus: use the polymyxin B for the based drug,combined with carbapenem antibiotics(meropenem,imipenem-(2)cilastatin sodium,biapenem);cefoperazone-sulbactam combined with carbapenems and doxycycline(3);tigecycline combined with carbapenems,polymyxin B and cefoperazone-sulbactam.According to the Clinical and Laboratory Standards Institute guidelines(CLSI,document M100-S25),we used microdilution method to determine the MIC of the drugs used in this study.The in vitro interactions of drug combination against AB isolates were determined by the checkerboard method.Drug interactions were interpreted by fractional inhibitory concentration index(FICI)model.In addition,we studied the antibacterial effects of non-antibacterial agents with antibacterial agents.The checkerboard method was also used to determine the antibacterial effect of chitosan,fluoxetine hydrochloride,artemisinin,ambroxol hydrochloride,amlodipine with polymyxin B,imipenem-cilastatin sodium against AB2.The FICI model was used to evaluate the experimental results.Then,we further expanded the number of isolates to study the combination effects of non-antibacterial agents with antibacterial agents.The checkerboard method was used to determine the in vitro antibacterial effects of ambroxol hydrochloride or amlodipine in combination with commonly used antibacterial agents,includeing meropenem,imipenemcilastatin sodium,biapenem,cefoperazone-sulbactam,polymyxin B and tigecycline,against six CRAB isolates.The results were evaluated by the FICI and ?E models.The formation of biofilm is one of the reasons for Acinetobacter Baumanii to becoming resistant,we first measured the ability to formatting biofilm of 6 AB strains using the method of semiquantitative staining with crystal violet.The chessboard method was used to determine the sMIC of polymyxin B with ABH or AML against AB2.The FICI model was used to interpret the interactions.Results 1.The antibacterial effect of the combination drug recommended by the guidelinesThe results showed that the 6 AB isolates used in this study were all resistant to carbapenems.In the consensus recommended above,the combination of polymyxin B with imipenem-cilastatin sodium showed synergistic effects against 2 AB isolates.The combination of cefoperazone-sulbactam with doxycycline showed synergistic effects against 3 isolates.When cefoperazone-sulbactam combined with biapenem or imipenem-cilastatin sodium,there were 2 or 1 isolate showed synergistic effects,respectively.For the combination of tigecycline with biapenem,only 1 isolate showed synergistic effect.The rest of the drug combination groups mainly exhibited additive effects.There was no antagonistic interactions in any of the tested drug combinations.2.Screening of synergistic combination groups of antibacterial with non-antibacterialThe results showed that the non-antibacterial drugs of fluoxetine hydrochloride,ambroxol hydrochloride(ABH)and amlodipine(AML)showed synergistic effects against AB2 when combined with polymyxin B.3.Antibacterial effect of ambroxol hydrochloride or amlodipine in combination with antibioticsIn this study,the combination of PB with AML exhibited synergistic interactions against all tested AB isolates,and PB plus ABH exhibited synergistic interactions against two isolates.The FICI and ?E model correlated very well for the combinations of PB with ABH and PB with AML against AB2.The rest of the drug combination groups mainly exhibited additive effects,such as the combination of carbapenems(MEM,IPM-CS,BPM)and SCF with ABH or AML.The combination of TGC with AML mainly showed additive effects,while the combination effects of TGC with ABH were not satisfying,only 2 strains showed additive effects.There were no antagonistic interactions in any of the tested drug combinations.4.The antibiofilms effects against the Acinetobacter baumannii of the combination group polymyxin B with ambroxol hydrochloride and amlodipineThe experiment results showed that all the 6 strains had strong ability to form biofilm,but AB2 has the strongest ability to form biofilm.And we found that,polymyxin B combined with ABH or AML showed synergistic anti-biofilm effects in different time.Conclusion 1.We studied the antibacterial effect of the two-drug combination against six strains of Acinetobacter baumannii from the “Laboratory diagnosis,clinical management and infection control of the infections caused by extensively drug-resistant Gram-negative bacilli: a Chinese consensus statement” in 2016.The results showed that the combination of polymyxin B plus imipenem-cilastatin sodium,cefoperazone-sulbactam plus doxycycline,biapenem,imipenem-cilastatin sodium,and tigecycline plus biapenem exhibited synergistic to a part of resistant AB,and the rest of the drug combination groups mainly exhibited additive effects.2.The combination of non-antibiotic agents,fluoxetine hydrochloride,ambroxol hydrochloride and amlodipine combined with polymyxin B showed synergistic effect.3.When the non-antibacterial agents ABH and AML combined with antibacterial agents against CRAB isolates,the combination of PB with AML exhibited synergistic interactions against all tested AB isolates,and PB plus ABH exhibited synergistic interactions against two isolates.The rest of the drug combination groups mainly exhibited additive effects.4.We found that,polymyxin B combined with ABH or AML showed synergistic antibiofilm effects in different time.