Antibacterial Effect Of Isopropoxy Benzene Guanidine Against Two Gram-positive Bacteria

In recent years,the spread of multi-drug resistant bacteria between bacterial pathogens poses a serious threat to global public health.Methylillin-resistant Staphylococcus aureus（methicillin-resistant Staphylococcus aureus,MRSA）is one of the main pathogens in hospital,community and animal infections,and its pathogenicity ranks first among Gram-positive bacteria.The pathogenicity of Enterococcus is second only to Staphylococcus aureus in Gram-positive bacteria,and the intrinsic resistance of MRSA and Enterococcus produces varying degrees of resistance to most antibiotics.With the successive reporting of vancomycin-resistant Staphylococcus aureus strains and enterococci strains,vancomycin is at risk as a"last line of defense"against Gram-positive bacteria.The use of existing compounds as antibacterial agents has become a hot topic,and current research progress includes the re-use of known safe compounds as new uses and the discovery of new antibacterial mechanisms.Substituted benzoquinone derivatives as a polymyxin antibiotic synergist,isopropoxy benzene guanidine（isopropoxy benzene guanidine,IBG）is one of the substituted phenylhydrazine derivatives,and IBC is found in bacteriostatic tests in vitro.The positive bacteria Staphylococcus aureus and Enterococcus have good antibacterial effects.In this study,Staphylococcus aureus standard strain(ATCC^?29213),Enterococcus faecium standard strain(ATCC^?219212)and clinical isolates were studied in vitro,by in vitro susceptibility,combination susceptibility,in vivo efficacy and bacterial cell membrane potential test.In vitro and in vivo antibacterial action and mechanism of action of IBG.The minimum inhibitory concentration（MIC）,minimum bactericidal concentration（MBC）and anti-mutation concentration（MPC）of the drug were determined by micro-broth dilution method.The dynamic in vitro bactericidal effect and mutation selection window of IBG were evaluated according to MIC,MBC and MPC.The bactericidal curve determines the concentration and time at which it exerts optimal efficacy.Taking ATCC^?29213 and methicillin-resistant Staphylococcus aureus 2-15 as research objects,IBG and ciprofloxacin（CIP）were used for drug resistance mutation experiments.The results showed that ciprofloxacin resistance gradually increased and continued.On the 14th day of subculture,the MIC of ciprofloxacin against Staphylococcus aureus ATCC^?29213 and methicillin-resistant Staphylococcus aureus 2-15 increased 512 times,and there was no significant change in MIC of IBG within 30 days.It indicates that the IBG compound has no resistance mutation to Staphylococcus aureus.A combination of IBG and gentamicin（GEN）,fosfomycin（FOS）,neomycin（NEO）and amikacin（AMK）for the in vitro antibacterial activity of Staphylococcus aureus using a checkerboard dilution method Has a synergistic effect.The in vivo pharmacodynamic effect of IBG was evaluated by establishing a model of mouse sepsis infection.Mice were infected with S.aureus strains containing the virulence gene sec A,sec C,and YXMC004P,and infected mice were inoculated by tail vein.The method is treated to comprehensively evaluate the in vivo antibacterial effect of IBG.The results show that IBG has certain anti-MRSA activity in vivo.At the same time,we used a fluorescence spectrophotometer to measure the changes in membrane potential of bacterial cells.It was determined that the target site of IBG was the bacterial cell membrane,and IBG destroyed the normal membrane potential of the cell membrane.The above results indicate that IBG has significant anti-S.aureus and Enterococcus activity in vitro and has certain anti-MRSA activity in vivo.The mechanism of action may be that after IBG destroys the normal membrane potential of bacteria,material exchange can not occur inside and outside the bacterial membrane,leading to bacterial death.At the same time,IBG is difficult to cause bacterial resistance mutations,and it has synergistic antibacterial effect in combination with some commonly used drugs.