Study On Antimicrobial Activity And Mechanism Of Antimicrobial Peptide Chensinin-1b On Multidrug-resistant Pseudomonas Aeruginosa

The emergence of multidrug-resistant bacteria poses a serious threat to human health and is the leading cause of clinical death.Therefore,the development of new mechanisms of action of antibiotics has become a new hot spot.Antimicrobial peptides are a kind of biologically active polypeptide produced by the coding of specific genes in the organism.It is an important member of the innate immune system.It has the advantages of broad antibacterial spectrum and no cytotoxicity to mammalian cells.The unique bactericidal mechanism of antimicrobial peptides makes it difficult for microbes to produce drug resistance and make it the most promising new antibiotic for multidrug resistant bacteria.Chensinin-1b,a derivative peptide of chensinin-1 that isolated and purified from the skin secretions of Rana chensinensis,has 10 positive charges and adopts an atypical conformation.Previous studies have found that chensinin-1b has a broad spectrum of antibacterial activity against a variety of Gram-positive and negative bacteria,including Pseudomonas aeruginosa.In this present study,the antibacterial activity and potential mode-of-action of chensinin-1b against clinically isolated multiple-drug-resistant P.aeruginosa(MRPA 0108)was determined in vivo,and further understand the mechanisms that participate in P.aeruginosa AMP resistance.The results showed that chensinin-1b exhibited antibacterial activity against a multiple-drug-resistant P.aeruginosa strain(MRPA0108)with a MIC of 25 μM;however,this value was significantly(16 times)lower than that observed against the susceptible P.aeruginosa(MIC 1.56 μM),suggesting that the resistance mechanism of multiple-drug-resistant P.aeruginosa affected the antibacterial activity of chensinin-1b.Chensinin-1b was able to disturb the integration of the cytoplasmic membrane of P.aeruginosa and MRPA 0108 cells similarly,but the outer membrane permeability of MRPA0108 cells was significantly lower.Furthermore,when the cell wall of MRPA0108 was removed,the antibacterial activity of chesnisinin-1b on MRPA0108 protoplasts significantly increased,the MIC value was 3.13 μM,close to MIC value against P.aeruginosa.This low permeability was associated with increased expression of LPS in the outer membrane and a decrease in negatively charged phospholipids in the outer membrane leaflet.Through the antibacterial peptide chensinin-1b and bacterial biofilm-related experiments,we found that antibacterial peptide chensinin-1b can inhibit the formation of bacterial biofilm and can also break down biofilm that has been formed,and the role of sensitive Pseudomonas aeruginosa better,And under the same conditions resistant Pseudomonas aeruginosa in thenumber of biofilm formation more advantages.The laser confocal microscopy also intuitively demonstrated that the biofilm of resistant Pseudomonas aeruginosa was thicker and the structure was more dense,Antibacterial peptides are less resistant to their decomposition.We also found that resistant Pseudomonas aeruginosa biofilm polysaccharide psl,pel content more,we can see that biofilm is also one of the main causes of bacterial resistance.