Enhancement of the antimicrobial activity and selectivity of GNU7 against Gram-negative bacteria by fusion with LPS-targeting peptide

Antimicrobial peptides (AMPs) provide a potential source of new antimicrobial therapeutics for the treatment of multidrug-resistant pathogens. To develop Gram-negative selective AMPs that can inhibit the effects of lipopolysaccharide (LPS)-induced sepsis, we added various rationally designed LPS-targeting peptides [amino acids 28–34 of lactoferrin (Lf28–34), amino acids 84–99 of bactericidal/permeability increasing protein (BPI84–99), and de novo peptide (Syn)] to the potent AMP, GNU7 (RLLRPLLQLLKQKLR). Compared to our original starting peptide GNU7, hybrid peptides had an 8- to 32-fold improvement in antimicrobial activity against Gram-negative bacteria, such as Escherichia coli and Salmonella typhimurium. Among them, Syn-GNU7 showed the strongest LPS-binding and -neutralizing activities, thus allowing it to selectively eliminate Gram-negative bacteria from within mixed cultures. Our results suggest that LPS-targeting peptides would be useful to increase the antimicrobial activity and selectivity of other AMPs against Gram-negative bacteria.     

Antimicrobial activity of an abiotic host defense peptide mimic

Bacterial drug resistance is emerging as one of the most significant challenges to human health. Antimicrobial peptides (AMPs), which are produced by many tissues and cell types of invertebrates, insects, and humans, as part of their innate immune system, have attracted considerable interest as alternative antibiotics. Interest in novel mimics of AMPs has increased greatly over the last few years. This report details a new AMP mimic, based on phenylene ethynylene, with improved antimicrobial activity and selectivity. Screening against a large set of bacterial and other organisms demonstrates broad spectrum antimicrobial activity including activity against antibiotic resistant bacterial like methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococci (VRE) as well as activity against yeast (Candida albicans) and fungus (Stachybotrys chartarum). Bacterial resistance development studies using Staphylococcus aureus show a rapid increase in MIC for conventional antibiotics, ciprofloxacin and norfloxacin. In sharp contrast, no change in MIC was observed for the AMP mimic. Cytotoxicity experiments show that the AMP mimic acts preferentially on microbes as opposed to mammalian red blood cells, 3T3 fibroblasts, and HEPG2 cells. In vivo experiments determined the maximum tolerated dose (MTD) to be 10 mg/kg suggesting a therapeutic window is available. These studies indicate that nonpeptidic amphiphilic AMP mimics could be developed as potential new treatments for antibiotic-resistant bacterial infections.     

Methodology for identification of pore forming antimicrobial peptides from soy protein subunits β-conglycinin and glycinin

Antimicrobial peptides (AMPs) inactivate microbial cells through pore formation in cell membrane. Because of their different mode of action compared to antibiotics, AMPs can be effectively used to combat drug resistant bacteria in human health. AMPs can also be used to replace antibiotics in animal feed and immobilized on food packaging films. In this research, we developed a methodology based on mechanistic evaluation of peptide-lipid bilayer interaction to identify AMPs from soy protein. Production of AMPs from soy protein is an attractive, cost-saving alternative for commercial consideration, because soy protein is an abundant and common protein resource. This methodology is also applicable for identification of AMPs from any protein. Initial screening of peptide segments from soy glycinin (11S) and soy β-conglycinin (7S) subunits was based on their hydrophobicity, hydrophobic moment and net charge. Delicate balance between hydrophilic and hydrophobic interactions is necessary for pore formation. High hydrophobicity decreases the peptide solubility in aqueous phase whereas high hydrophilicity limits binding of the peptide to the bilayer. Out of several candidates chosen from the initial screening, two peptides satisfied the criteria for antimicrobial activity, viz. (i) lipid-peptide binding in surface state and (ii) pore formation in transmembrane state of the aggregate. This method of identification of antimicrobial activity via molecular dynamics simulation was shown to be robust in that it is insensitive to the number of peptides employed in the simulation, initial peptide structure and force field. Their antimicrobial activity against Listeria monocytogenes and Escherichia coli was further confirmed by spot-on-lawn test.     

Escherichia coli Cell Surface Perturbation and Disruption Induced by Antimicrobial Peptides BP100 and pepR

The potential of antimicrobial peptides (AMPs) as an alternative to conventional therapies is well recognized. Insights into the biological and biophysical properties of AMPs are thus key to understanding their mode of action. In this study, the mechanisms adopted by two AMPs in disrupting the Gram-negative Escherichia coli bacterial envelope were explored. BP100 is a short cecropin A-melittin hybrid peptide known to inhibit the growth of phytopathogenic Gram-negative bacteria. pepR, on the other hand, is a novel AMP derived from the dengue virus capsid protein. Both BP100 and pepR were found to inhibit the growth of E. coli at micromolar concentrations. Zeta potential measurements of E. coli incubated with increasing peptide concentrations allowed for the establishment of a correlation between the minimal inhibitory concentration (MIC) of each AMP and membrane surface charge neutralization. While a neutralization-mediated killing mechanism adopted by either AMP is not necessarily implied, the hypothesis that surface neutralization occurs close to MIC values was confirmed. Atomic force microscopy (AFM) was then employed to visualize the structural effect of the interaction of each AMP with the E. coli cell envelope. At their MICs, BP100 and pepR progressively destroyed the bacterial envelope, with extensive damage already occurring 2 h after peptide addition to the bacteria. A similar effect was observed for each AMP in the concentration-dependent studies. At peptide concentrations below MIC values, only minor disruptions of the bacterial surface occurred.     

Piscidin,Fish Antimicrobial Peptide: Structure,Classification, Properties,Mechanism, Gene Regulation and Therapeutical Importance

Antimicrobial peptides (AMPs) are short molecules produced by almost all organisms. Fish AMPs contain innate immune components as their primary immune molecules. The fish AMPs include piscidins, hepcidins, defensins, cathelicidins and histone-derived peptides. Piscidin is potent and broad-spectrum; this peptide was conserved among Acanthopterygii superorder and is therapeutically important among other AMPs. It was present mainly in the tissues of gills, muscle, head-kidney, skin and intestine of teleost. Piscidin AMP family includes piscidin, moronecidin, pleurocidin, epinecidin, gaduscidin, misgurin, dicentracin, chrysophsin and myxinidin. This review reports the structural properties of various piscidin and their mode of action as it is important to know their mechanism how the peptide involved in antimicrobial activity. In addition, the gene expression of piscidin which influenced the immune responses, their pharmaceutical importance and biological applications were described. Overall, the review explains a broad spectrum of knowledge on piscidin, its classes and types, structure, cytotoxicity, membrane permeabilization, properties and therapeutical implications.

     

Two novel families of antimicrobial peptides from skin secretions of the Chinese torrent frog, Amolops jingdongensis

The characterization of new natural antimicrobial peptides (AMPs) can help to solve the serious problem of bacterial resistance to currently used antibiotics. In the current study, we analyzed two families of AMPs from the Chinese torrent frog Amolops jingdongensis with a range of bioactivities. The first family of peptides, named jindongenin-1a, is 24 amino acids in length; a BLAST search of jindongenin-1a revealed no sequence similarity with other AMPs. The second family consists of two peptides containing 29 amino acid residues each. These peptides have high sequence similarity with the AMPs of palustrin-2 and are therefore designated palustrin-2AJ1 and palustrin-2AJ2. The cDNA sequences encoding these AMPs have been cloned and the deduced protein sequence of each AMP has been determined by protein sequencing. Sequence and structural analysis showed that each precursor is composed of a putative signal peptide, an N-terminal spacer, a processing site and a disulfide-bridged heptapeptide segment at the C-terminus. We synthesized jindongenin-1a and palustrin-AJ1 to test their antimicrobial, hemolytic, antioxidative and cytotoxic activities. These two peptides showed broad-spectrum antimicrobial activity to standard and clinically isolated strains of bacteria. In addition, they exhibited weak hemolytic activity to human and rabbit erythrocytes under our experimental conditions. Moreover, these peptides also displayed cytotoxic activity against the K562 and HT29 mammalian cell lines and low anti-oxidant activity. These findings provide helpful insight that will be useful in the design of anti-infective peptide agents.     

Studies on anticancer activities of antimicrobial peptides

In spite of great advances in cancer therapy, there is considerable current interest in developing anticancer agents with a new mode of action because of the development of resistance by cancer cells towards current anticancer drugs. A growing number of studies have shown that some of the cationic antimicrobial peptides (AMPs), which are toxic to bacteria but not to normal mammalian cells, exhibit a broad spectrum of cytotoxic activity against cancer cells. Such studies have considerably enhanced the significance of AMPs, both synthetic and from natural sources, which have been of importance both for an increased understanding of the immune system and for their potential as clinical antibiotics. The electrostatic attraction between the negatively charged components of bacterial and cancer cells and the positively charged AMPs is believed to play a major role in the strong binding and selective disruption of bacterial and cancer cell membranes, respectively. However, it is unclear why some host defense peptides are able to kill cancer cells when others do not. In addition, it is not clear whether the molecular mechanism(s) underlying the antibacterial and anticancer activities of AMPs are the same or different. In this article, we review various studies on different AMPs that exhibit cytotoxic activity against cancer cells. The suitability of cancer cell-targeting AMPs as cancer therapeutics is also discussed.     

In vitro activity of novel in silico‐developed antimicrobial peptides against a panel of bacterial pathogens

Antimicrobial‐peptide‐based therapies could represent a reliable alternative to overcome antibiotic resistance, as they offer potential advantages such as rapid microbicidal activity and multiple activities against a broad spectrum of bacterial pathogens. Three synthetic antimicrobial peptides (AMPs), AMP72, AMP126, and also AMP2041, designed by using ad hoc screening software developed in house, were synthesized and tested against nine reference strains. The peptides showed a partial β‐sheet structure in 10‐mM phosphate buffer. Low cytolytic activity towards both human cell lines (epithelial, endothelial, and fibroblast) and sheep erythrocytes was observed for all peptides. The antimicrobial activity was dose dependent with a minimum bactericidal concentration (MBC) ranging from 0.17 to 10.12 μM (0.4–18.5 µg/ml) for Gram‐negative and 0.94 to 20.65 μM (1.72‐46.5 µg/ml) for Gram‐positive bacteria. Interestingly, in high‐salt environment, the antibacterial activity was generally maintained for Gram‐negative bacteria. All peptides achieved complete bacterial killing in 20 min or less against Gram‐negative bacteria. A linear time‐dependent membrane permeabilization was observed for the tested peptides at 12.5 µg/ml. In a medium containing Mg²⁺ and Ca²⁺, the peptide combination with EDTA restores the antimicrobial activity particularly for AMP2041. Moreover, in combination with anti‐infective agents (quinolones or aminoglycosides) known to bind divalent cation, AMP126 and AMP2041 showed additive activity in comparison with colistin. Our results suggest the following: (i) there is excellent activity against Gram‐negative bacteria, (ii) there is low cytolytic activity, (iii) the presence of a chelating agent restores the antimicrobial activity in a medium containing Mg²⁺ and Ca²⁺, and (iv) the MBC value of the combination AMPs–conventional antibiotics was lower than the MBC of single agents alone. Copyright © 2013 European Peptide Society and John Wiley & Sons, Ltd.     

Evaluation of antibacterial activity induced by Staphylococcus aureus and Ent A in the hemolymph of Spodoptera littoralis

The problem of antibiotic resistance considers one of the most dangerous challenges facing the medical field. So, it is necessary to find substitutions to conventional antibiotics. Antimicrobial peptides (AMPs) are a bio-functional derivative that have been observed as one of the important solutions to such upcoming crisis. Owing to their role as the first line of defense against bacteria, fungi, and viruses. This study was conducted to induce the immune response of Spodoptera littoralis larvae by inoculation of sub lethal doses of Staphylococcus aureus and its enterotoxin. Since Staphylococcal enterotoxin A (SEA) considers the major causative agents of Staphylococcal food poisoning, our study oriented to purify and characterize this toxin to provoke its role in yielding AMPs with broad spectrum antimicrobial activity. A great fluctuation was recorded in the biochemical properties of immunized hemolymph not only in the total protein content but also protein banding pattern. Protein bands of ∼22 kDa (attacin-like) and ∼15 kDa (lysozyme-like) were found to be common between the AMPs induced as a result of both treatments. While protein bands of molecular weight ∼70 kDa (phenoloxidase-like) and ∼14 kDa (gloverin-like) were found specific for SEA treatment. Chromatographic analysis using HPLC for the induced AMPs showed different types of amino acids appeared with differences in their quantities and velocities. These peptides exhibited noticeable antimicrobial activity against certain Gram-positive and Gram-negative bacteria. In conclusion, the antimicrobial potential of the antimicrobial peptides (AMP) induced in the larval hemolymph of S. littoralis will be a promising molecule for the development of new therapeutic alternatives.     

Outer membrane lipoprotein Lpp is Gram-negative bacterial cell surface receptor for cationic antimicrobial peptides

Antimicrobial peptides/proteins (AMPs) are important components of the host innate defense mechanisms. Here we demonstrate that the outer membrane lipoprotein, Lpp, of Enterobacteriaceae interacts with and promotes susceptibility to the bactericidal activities of AMPs. The oligomeric Lpp was specifically recognized by several cationic α-helical AMPs, including SMAP-29, CAP-18, and LL-37; AMP-mediated bactericidal activities were blocked by anti-Lpp antibody blocking. Blebbing of the outer membrane and increase in membrane permeability occurred in association with the coordinate internalization of Lpp and AMP. Interestingly, the specific binding of AMP to Lpp was resistant to divalent cations and salts, which were able to inhibit the bactericidal activities of some AMPs. Furthermore, using His-tagged Lpp as a ligand, we retrieved several characterized AMPs, including SMAP-29 and hRNase 7, from a peptide library containing crude mammalian cell lysates. Overall, this study explores a new mechanism and target of antimicrobial activity and provides a novel method for screening of antimicrobials for use against drug-resistant bacteria.     

Stepwise identification of potent antimicrobial peptides from human genome

The increasing incidence of hospital acquired infections caused by antibiotic resistant pathogens has led to an increase in morbidity and mortality, finding alternative antibiotics unaffected by resistance mechanisms is fundamentally important for treating this problem. Naturally occurring proteins usually carry short peptide fragments that exhibit noticeable biological activity against a wide variety of microorganisms such as bacteria, fungi and protozoa. Traditional discovery of such antimicrobially active fragments (i.e. antimicrobial peptides, AMPs) from protein repertoire is either random or led by chance. Here, we report the use of a rational protocol that combines in silico prediction and in vitro assay to identify potential AMPs with high activity and low toxicity from the entire human genome. In the procedure, a three-step inference strategy is first proposed to perform genome-wide analysis to infer AMPs in a high-throughput manner. By employing this strategy we are able to screen more than one million peptide candidates generated from various human proteins, from which we identify four highly promising samples, and subsequently their antibacterial activity on five strains as well as cytotoxicity on human myoblasts are tested experimentally. As a consequence, two high-activity, low-toxicity peptides are discovered, which could be used as the structural basis to further develop new antibiotics. In addition, from 1491 known AMPs we also derive a quantitative measure called antibacterial propensity index (API) for 20 naturally occurring amino acids, which shows a significant allometric correlation with the theoretical minimal inhibitory concentration of putative peptides against Gram-positive and Gram-negative bacteria. This study may provide a proof-of-concept paradigm for the genome-wide discovery of novel antimicrobial peptides by using a combination of in silico and in vitro analyses.     

Inhibition and destruction of Pseudomonas aeruginosa biofilms by antibiotics and antimicrobial peptides

Pseudomonas aeruginosa is one of the major nosocomial pathogen that can causes a wide variety of acute and chronic infections P. aeruginosa is a dreaded bacteria not just because of the high intrinsic and acquired antibiotic resistance rates but also the biofilm formation and production of multiple virulence factors. We investigated the in vitro activities of antibiotics (ceftazidime, tobramycin, ciprofloxacin, doripenem, piperacillin and colistin) and antimicrobial cationic peptides (AMPs; LL-37, CAMA: cecropin(1–7)-melittin A(2–9) amide, melittin, defensin and magainin-II) alone or in combination against biofilms of laboratory strain ATCC 27853 and 4 clinical strains of P. aeruginosa. The minimum inhibitory concentrations (MIC), minimum bactericidal concentration (MBC) and minimum biofilm eradication concentrations (MBEC) were determined by microbroth dilution technique. The MBEC values of antibiotics and AMPs were 80–>5120 and 640–>640 mg/L, respectively. When combined with the LL-37 or CAMA at 1/10× MBEC, the MBEC values of antibiotics that active against biofilms, were decreased up to 8-fold. All of the antibiotics, and AMPs were able to inhibit the attachment of bacteria at the 1/10× MIC and biofilm formation at 1× or 1/10× MIC concentrations. Time killing curve studies showed 3-log₁₀ killing against biofilms in 24 h with almost all studied antibiotics and AMPs. Synergism were seen in most of the studied combinations especially CAMA/LL-37 + ciprofloxacin against at least one or two strains’ biofilms. Since biofilms are not affected the antibiotics at therapeutic concentrations, using a combination of antimicrobial agents including AMPs, or inhibition of biofilm formation by blocking the attachment of bacteria to surfaces might be alternative methods to fight with biofilm associated infections.     

Antimicrobial properties of membrane-active dodecapeptides derived from MSI-78

Antimicrobial peptides (AMPs) are a class of broad-spectrum antibiotics known by their ability to disrupt bacterial membranes and their low tendency to induce bacterial resistance, arising as excellent candidates to fight bacterial infections. In this study we aimed at designing short 12-mer AMPs, derived from a highly effective and broad spectrum synthetic AMP, MSI-78 (22 residues), by truncating this peptide at the N- and/or C-termini while spanning its entire sequence with 1 amino acid (aa) shifts. These designed peptides were evaluated regarding antimicrobial activity against selected gram-positive Staphylococcus strains and the gram-negative Pseudomonas aeruginosa (P. aeruginosa).The short 12-mer peptide CEM1 (GIGKFLKKAKKF) was identified as an excellent candidate to fight P. aeruginosa infections as it displays antimicrobial activity against this strain and selectivity, with negligible toxicity to mammalian cells even at high concentrations. However, in general most of the short 12-mer peptides tested showed a reduction in antimicrobial activity, an effect that was more pronounced for gram-positive Staphylococcus strains. Interestingly, CEM1 and a highly similar peptide differing by only one aa-shift (CEM2: IGKFLKKAKKFG), showed a remarkably contrasting AMP activity. These two peptides were chosen for a more detailed study regarding their mechanism of action, using several biophysical assays and simple membrane models that mimic the mammalian and bacterial lipid composition.We confirmed the correlation between peptide helicity and antimicrobial activity and propose a mechanism of action based on the disruption of the bacterial membrane permeability barrier.     

改良型抗菌肽的研究进展

长期滥用抗生素导致了耐药菌株“超级细菌”的出现,增加了动物、人类健康和环境污染风险．寻找抗生素替代品正成为全球研究热点,抗菌肽因其高效抗菌效果和不同于抗生素的独特作用机制引起了各国研究者的关注,并进行了相关研究．然而抗菌肽的安全性、稳定性、生产成本等问题限制了其生产与应用．为了克服这些不利因素,研究者们对抗菌肽进行了多种方式的改造,产生了模拟型、同源型、杂合型、轭合型、稳定型和固位型等改良型抗菌肽,并有望在畜牧业、食品业、医药业等领域得到广泛的应用．本文主要综述了这些改良型抗菌肽近年来的研究进展．     

Flexibility is a mechanical determinant of antimicrobial activity for amphipathic cationic α-helical antimicrobial peptides

Antimicrobial peptides (AMPs) are recognized as the potential substitutions for common antibiotics. Flexibility has been demonstrated to be a dominant on antimicrobial activity of an AMP, similar to the structural parameters such as hydrophobicity and hydrophobic moment as well as positive charge. To better understand the effect of flexibility on antimicrobial activity, we herein examined seventy-eight peptides derived from nine different species. Defined as a weighted average of amino acid flexibility indices over whole residue chain of AMP, flexibility index was used to scale the peptide flexibility and indicated to be a reflection of mechanical properties such as tensile and flexural rigidities. The results demonstrated that flexibility index is relevant to but different from other structural properties, may enhance activity against Escherichia coli for stiff clustered peptides or reduce activity against E. coli for flexible clustered peptides, and its optimum occurs at about − 0.5. This effect of flexibility on antimicrobial activity may be involved to the antimicrobial actions, such as stable peptide-bound leaflet formation and sequent stress concentration in target cell membrane, mechanically. The present results provide a new insight in understanding antimicrobial actions and may be useful in seeking for a new structure–activity relationship for cationic and amphipathic α-helical peptides.     

A Novel Antimicrobial Peptide Derived from the Insect Paederus dermatitis

Much research has been focused on antimicrobial peptides (AMPs) derived from insect immune defense reactions due to their potential in the development of new antibiotics. In this study, a new AMP from the insect Paederus dermatitis, named sarcotoxin Pd was identified and purified using gel filtration and reverse-phase high-performance liquid chromatography. Our results showed that this peptide has broad-spectrum inhibitory effects on examined microbes. Sarcotoxin Pd is composed of 34 amino acids and its molecular weight was estimated to be 3613.26 ± 0.5 Da. Minimum inhibitory concentration (MIC) values of sarcotoxin Pd against Gram-negative bacteria were lower than Gram-positive bacteria and fungi. The identified peptide showed the highest antimicrobial effect against Klebsiella pneumonia and Escherichia coli. This peptide did not reveal significant hemolytic activity against human red blood cells particularly in the range of MIC values. Confirming the potential antimicrobial activities of synthetic peptide, this paper addresses the role of sarcotoxin Pd in the treatment of systemic microbial illnesses.     

Broad activity against porcine bacterial pathogens displayed by two insect antimicrobial peptides moricin and cecropin B

In response to infection, insects produce a variety of antimicrobial peptides (AMPs) to kill the invading pathogens. To study their physicochemical properties and bioactivities for clinical and commercial use in the porcine industry, we chemically synthesized the mature peptides Bombyx mori moricin and Hyalophora cecropia cecropin B. In this paper, we described the antimicrobial activity of the two AMPs. Moricin exhibited antimicrobial activity on eight strains tested with minimal inhibitory concentration values (MICs) ranging between 8 and 128 μg/ml, while cecropin B mainly showed antimicrobial activity against the Gramnegative strains with MICs ranging from 0.5 to 16 μg/ml. Compared to the potent antimicrobial activity these two AMPs displayed against most of the bacterial pathogens tested, they exhibited limited hemolytic activity against porcine red blood cells. The activities of moricin and cecropin B against Haemophilus parasuis SH 0165 were studied in further detail. Transmission electron microscopy (TEM) of moricin and cecropin B treated H. parasuis SH 0165 indicated extensive damage to the membranes of the bacteria. Insights into the probable mechanism utilized by moricin and cecropin B to eliminate pathogens are also presented. The observations from this study are important for the future application of AMPs in the porcine industry.     

Predicting Therapeutic Template by Evaluating the Structural Stability of Anti-Cancer Peptides—A Computational Approach

Clinically significant antibiotic resistance has evolved against virtually every antibiotic deployed. Yet the development of new classes of antibiotics has lagged far behind our growing need for such drugs. Antimicrobial peptides (AMPs) have emerged as novel therapeutics hailed for their bactericidal and immunomodulatory properties. However, the process of optimizing antimicrobial peptide stability, using large peptide libraries is both tedious and expensive. The intent of this study is to analyze computationally the stability of anti-cancer peptides (ACPs) and to discover a potential template from a pool of ACPs for therapeutic use. Consequently we highlighted that ACP, NK-Lysin appears advantageous over the other ACPs with respect to stability, and may provide a convenient platform for the development of anticancer therapeutic peptide.     

In silico design of polycationic antimicrobial peptides active against <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis> and <Emphasis Type="Italic">Staphylococcus aureus</Emphasis>

Antimicrobial peptides (AMPs) have the potential to become valuable antimicrobial drugs in the coming years, since they offer wide spectrum of action, rapid bactericidal activity, and low probability for resistance development in comparison with traditional antibiotics. The search and improvement of methodologies for discovering new AMPs to treat resistant bacteria such as Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii and Pseudomonas aeruginosa are needed for further development of antimicrobial products. In this work, the software Peptide ID 1.0^® was used to find new antimicrobial peptide candidates encrypted in proteins, considering the physicochemical parameters characteristics of AMPs such as positive net charge, hydrophobicity, and sequence length, among others. From the selected protein fragments, new AMPs were designed after conservative and semi-conservative modifications and amidation of the C-terminal region. In vitro studies of the antimicrobial activity of the newly designed peptides showed that two peptides, P3-B and P3-C, were active against P. aeruginosa Escherichia coli and A. baumannii with low minimum inhibitory concentrations. Peptide P3-C was also active against K. pneumoniae and S. aureus. Furthermore, bactericidal activity and information on the possible mechanisms of action are described according to the scanning electron microscopy studies.