Potency Of Antimicrobial Peptides Research Articles

A novel antimicrobial peptide MP-4: Insights into its antimicrobial properties and intestinal regulation on E. coli-infected mice

The quest for novel, potent antimicrobial agents with low resistance potential poses a significant challenge for the advancement of the food and medical sectors. This study aimed to elucidate the antibacterial potency of antimicrobial peptides derived from koumiss in a murine model. Leveraging an antimicrobial peptide database, six peptides (MP-1 to MP-6) were meticulously predicted and screened for their antibacterial properties. These peptides were subsequently synthesized using chemical solid-phase methods and their antibacterial activities were rigorously validated. Remarkably, among the six peptides, MP-4 demonstrated a profound antibacterial effect against E. coli, achieving rapid bacterial eradication within 240 min. Flow cytometry analysis further corroborated its significant bactericidal activity. In vivo experiments conducted on mice infected with E. coli revealed that oral administration of MP-4 significantly ameliorated symptoms such as lethargy, anorexia, and weight loss. Additionally, it effectively reduced the colonic E. coli burden, attenuated inflammatory responses, and favorably modulated the intestinal microbiota composition. This study not only validates the robust antibacterial activity of the koumiss-derived antimicrobial peptide MP-4, but also underscores its potential therapeutic application in mitigating E. coli infections and promoting intestinal health.

A Robust Strategy Against Multi-Resistant Pathogens in Oral Health: Harnessing the Potency of Antimicrobial Peptides in Nanofiber-Mediated Therapies

A Robust Strategy Against Multi-Resistant Pathogens in Oral Health: Harnessing the Potency of Antimicrobial Peptides in Nanofiber-Mediated Therapies

Dissecting the Therapeutic Potency of Antimicrobial Peptides Against Microbial Biofilms.

Microbial resistance to conventional therapeutics has become a significant threat to human society. Biofilms serve as the major virulence factor for the microorganisms by resisting the antibiotics and host innate immune system. Antimicrobial peptides (AMPs) have emerged as a potential alternative to conventional therapeutics due to their exceptional anti-biofilm and broad-spectrum antimicrobial property. Researchers have applied bioinformatics, genetic engineering, tissue culture, and drug delivery approaches to enhance the production and therapeutic efficacy of antimicrobial peptides. This review comprehensively describes the various aspects of AMPs with particular focus on their anti-biofilm potential. Other detailed information highlighted in this review includes different classes of AMPs, their mode of action, and anti-biofilm activity both alone and in synergy with other AMPs or conventional antibiotics. Further, challenges and opportunities of AMPs based drug delivery systems such as nano-formulations, polymeric micelles, and vesicles are also summarized.

Enhancing Antimicrobial Peptide Potency through Multivalent Presentation on Coiled-Coil Nanofibrils.

Antibiotic-resistant microbes have become a global health threat. New delivery systems that enhance the efficacy of antibiotics and/or overcome the resistances can help combat them. In this context, we present FF03, a fibril-forming α-helical coiled-coil peptide that functions as an efficient scaffold for the multivalent presentation of the weakly cationic antimicrobial peptide (AMP) IN4. The resulting IN4-decorated FF03 coiled-coil fibrils (FF03 + IN4) are nonhemolytic and noncytotoxic and show enhanced antimicrobial activity relative to unconjugated IN4 and standard antibiotics against several bacterial strains. Scanning electron microscopy analysis shows that FF03 + IN4 nanofibers disrupt methicillin-resistant Staphylococcus aureus membranes, indicating a surface-level mode of action. Furthermore, transmission electron microscopy and circular dichroism studies indicate that decoration of the FF03 scaffold with IN4 does not alter the secondary-structure propensity or fibril-forming properties of FF03. Thus, the approach reported herein provides a new peptidic scaffold for the multivalent presentation of AMPs to obtain nonhemolytic and noncytotoxic antimicrobial systems with improved efficacy relative to the unconjugated AMP analogues.

Purification and characterization of antimicrobial peptide fractions of Junipers seravschanica

Abstract The emergence of antibiotic resistance among bacteria leads to the urge of finding an alternative solution. Therefore, antimicrobial peptides (AMPs) have emerged as a promisingly new group of therapeutic agents for managing infectious diseases. This research was designed to explore the potency of antimicrobial peptides from Omani Juniperus seravschanica plant and their mode of action. The isolated AMPs showed to have inhibitory activity towards pathogenic bacteria namely Bacillus subtilis, Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Micrococcus luteus, Methicillin-resistant Staphylococcus aureus (MRSA) and fungi such as Aspergillus flavus, and Cladosporium herbarum. The isolated AMPs showed noticeable changes in OD, illustrating clearly the pore formation. Scanning electron microscope showed significant membrane disruption of the bacteria. The three AMP fractions displayed to be heat stable and functioned well at low pH (2–6). Therefore, further studies are recommended to explore the real potential of immobilized AMPs in health applications as antimicrobial coatings of medical devices.

Computational Peptide Engineering Approach for Selection the Best Engendered Camel Lactoferrin-Derive Peptide with Potency to Interact with DNA

Antimicrobial peptides (AMPs) are native and safe short peptides with valuable biological effects. Nowadays, these components and their importance have attracted the attention of many researchers to determine their mode of action. Computational peptide engineering can donate a useful insight for investigating the stability and potency of AMPs. In the present study, to improve the effect of CLF36, a chimeric peptide derived camel lactoferrin, the atomic insight into peptide-DNA interaction was analyzed using MD simulation. Targeted mutants were performed in wild type amino acid sequences and obtained engineered peptides were homology modeled for peptide-DNA interaction analysis. SASA, Hydrogen binding and free binding energy analyses revealed that all changes in wild type of peptide in this study improved the peptide-DNA interaction. Our in silico results showed that simultaneous substitution of GLU12 with ALA and also removing SER36 in wild type had more substantial effects on complex formation with DNA. The obtained result of this study could be useful to improve the stability and potency of engineered peptides to use of in the experimental study.

Temporin L and aurein 2.5 have identical conformations but subtly distinct membrane and antibacterial activities

Frogs such as Rana temporaria and Litoria aurea secrete numerous closely related antimicrobial peptides (AMPs) as an effective chemical dermal defence. Damage or penetration of the bacterial plasma membrane is considered essential for AMP activity and such properties are commonly ascribed to their ability to form secondary amphipathic, α-helix conformations in membrane mimicking milieu. Nevertheless, despite the high similarity in physical properties and preference for adopting such conformations, the spectrum of activity and potency of AMPs often varies considerably. Hence distinguishing apparently similar AMPs according to their behaviour in, and effects on, model membranes will inform understanding of primary-sequence-specific antimicrobial mechanisms. Here we use a combination of molecular dynamics simulations, circular dichroism and patch-clamp to investigate the basis for differing anti-bacterial activities in representative AMPs from each species; temporin L and aurein 2.5. Despite adopting near identical, α-helix conformations in the steady-state in a variety of membrane models, these two AMPs can be distinguished both in vitro and in silico based on their dynamic interactions with model membranes, notably their differing conformational flexibility at the N-terminus, ability to form higher order aggregates and the characteristics of induced ion conductance. Taken together, these differences provide an explanation of the greater potency and broader antibacterial spectrum of activity of temporin L over aurein 2.5. Consequently, while the secondary amphipathic, α-helix conformation is a key determinant of the ability of a cationic AMP to penetrate and disrupt the bacterial plasma membrane, the exact mechanism, potency and spectrum of activity is determined by precise structural and dynamic contributions from specific residues in each AMP sequence.

Modulation of Antimicrobial Peptide Potency in Stressed Lipid Bilayers.

It is shown that the tendency of an archetypal antimicrobial peptide to insert into and perforate a simple lipid bilayer is strongly modulated by tensile stress in the membrane. The results, obtained through molecular dynamics simulations, have been demonstrated with several lipid compositions and appear to be general, although quantitative details differ. The findings imply that the potency of antimicrobial peptides may not be a purely intrinsic chemical property and, instead, depends on the mechanical state of the target membrane.

Topological effects on the designability and bactericidal potency of antimicrobial peptides

New ideas and methods are being developed to generate highly designable small functional protein folds beyond the confines of natural structures, from secondary to quaternary level. Highly designable folds can have multiple sequence solutions, which are thermodynamically and kinetically stable. We have previously described how short syndiotactic helices can be exceptionally stable energetically, and how they can be used as a template for designing antibacterial agents. In this work, we have designed four syndiotactic, single turn, amphipathic; cationic 7-mer peptides which are the sequence and structural subset of earlier published 12-mer sequences. We examined the stability of the designed structures and its effects on the biological activity of such short peptide sequences. This was achieved by making objective comparisons between 12-mer and 7-mer sequences in terms of their antibacterial activity. Further, we investigated the mechanistic origins of clearly different bactericidal potency of single (7-mer) and double (12-mer) turn syndiotactic helices using molecular dynamics simulations. Our results suggest that conformationally constrained stable short double turn peptide scaffolds are highly designable, whereas single turn structures are more likely to be disordered. The stability of the designed peptide structure provides a platform for inclusion of multiple sequence variables and defined electrostatic fingerprints. Therefore, a stable peptide scaffold along with pre-defined electrostatic signatures can together be utilized for the design of novel antimicrobial peptides.

Enhancing the Potency of Antimicrobial Peptides through Molecular Engineering and Self-Assembly.

Healthcare-associated infections resulting from bacterial attachment and biofilm formation on medical implants are posing significant challenges in particular with the emergence of bacterial resistance to antibiotics. Here, we report the design, synthesis and characterization of self-assembled nanostructures, which integrate on their surface antibacterial peptides. The antibacterial WMR peptide, which is a modification of the native sequence of the myxinidin, a marine peptide isolated from the epidermal mucus of hagfish, was used considering its enhanced activity against Gram-negative bacteria. WMR was linked to a peptide segment of aliphatic residues (AAAAAAA) containing a lipidic tail (C19H38O2) attached to the ε-amino of a terminal lysine to generate a peptide amphiphile (WMR PA). The self-assembly of the WMR PA alone, or combined with coassembling shorter PAs, was studied using spectroscopy and microscopy techniques. The designed PAs were shown to self-assemble into stable nanofiber structures and these nanoassemblies significantly inhibit biofilm formation and eradicate the already formed biofilms of Pseudomonas aeruginosa (Gram-negative bacteria) and Candida albicans (pathogenic fungus) when compared to the native WMR peptide. Our results provide insights into the design of peptide based supramolecular assemblies with antibacterial activity, and establish an innovative strategy to develop self-assembled antimicrobial materials for biomedical applications.

Correlation of an Antimicrobial Peptide's Potency and Its Influences on Membrane Elasticity

The killing power of membrane-active antimicrobial peptides (AMPs) lies in their ability to disrupt the structures of pathogenic membranes. While understanding the AMPs' mechanisms of action is key to realizing their therapeutic potentials, how the AMPs modulate membrane elasticity and thereby affect membrane structure remains an open question, even though the AMP-induced variations in membrane curvature are widely considered to be crucial. Here, we exploit the x-ray diffraction technique to examine how the dominant bacterial lipid, phosphatidylethanolamine, varies its monolayer elastic properties upon interacting with six artificial peptides mimicking the AMPs' common amino acid content. Remarkably, the monolayer spontaneous curvature ${C}_{0}$ is unaffected by any of the peptides. In contrast, the peptides designated as ${(\mathrm{K}2\mathrm{W})}^{2}$, K4W2, R6, and R9, mimicking the AMP mutants with microbicidal potency, are able to modify the monolayer bending moduli ${K}_{cp}$, while those derived from the impotent mutants cannot. The results are consistent with the scenario that the AMPs disrupt the structure of pathogenic monolayers by, additionally if not exclusively, modulating their ${K}_{cp}$'s, with stiffening and softening leading to two different modes of disruption, that is, toroidal pore formation and membrane micellation, respectively.

Correlation of an antimicrobial peptide's potency and its influences on membrane elasticity

The killing power of membrane-active antimicrobial peptides (AMPs) lies in their ability to disrupt the structures of pathogenic membranes. While understanding the AMPs' mechanisms of action is key to realizing their therapeutic potentials, how the AMPs modulate membrane elasticity and thereby affect membrane structure remains an open question, even though the AMP-induced variations in membrane curvature are widely considered to be crucial. Here, we exploit the x-ray diffraction technique to examine how the dominant bacterial lipid, phosphatidylethanolamine, varies its monolayer elastic properties upon interacting with six artificial peptides mimicking the AMPs' common amino acid content. Remarkably, the monolayer spontaneous curvature ${C}_{0}$ is unaffected by any of the peptides. In contrast, the peptides designated as ${(\mathrm{K}2\mathrm{W})}^{2}$, K4W2, R6, and R9, mimicking the AMP mutants with microbicidal potency, are able to modify the monolayer bending moduli ${K}_{cp}$, while those derived from the impotent mutants cannot. The results are consistent with the scenario that the AMPs disrupt the structure of pathogenic monolayers by, additionally if not exclusively, modulating their ${K}_{cp}$'s, with stiffening and softening leading to two different modes of disruption, that is, toroidal pore formation and membrane micellation, respectively.

Designing Antibacterial Peptides with Enhanced Killing Kinetics.

Antimicrobial peptides (AMPs) are gaining attention as substitutes for antibiotics in order to combat the risk posed by multi-drug resistant pathogens. Several research groups are engaged in design of potent anti-infective agents using natural AMPs as templates. In this study, a library of peptides with high sequence similarity to Myeloid Antimicrobial Peptide (MAP) family were screened using popular online prediction algorithms. These peptide variants were designed in a manner to retain the conserved residues within the MAP family. The prediction algorithms were found to effectively classify peptides based on their antimicrobial nature. In order to improve the activity of the identified peptides, molecular dynamics (MD) simulations, using bilayer and micellar systems could be used to design and predict effect of residue substitution on membranes of microbial and mammalian cells. The inference from MD simulation studies well corroborated with the wet-lab observations indicating that MD-guided rational design could lead to discovery of potent AMPs. The effect of the residue substitution on membrane activity was studied in greater detail using killing kinetic analysis. Killing kinetics studies on Gram-positive, negative and human erythrocytes indicated that a single residue change has a drastic effect on the potency of AMPs. An interesting outcome was a switch from monophasic to biphasic death rate constant of Staphylococcus aureus due to a single residue mutation in the peptide.

Biological consequences of improving the structural stability of hairpins that have antimicrobial activity.

Designing new antimicrobial peptides (AMPs) focuses heavily on the activity of the peptide and less on the elements that stabilize the secondary structure of these peptides. Studies have shown that improving the structure of naturally occurring AMPs can affect activity and so here we explore the relationship between structure and activity of two non-naturally occurring AMPs. We have used a backbone-cyclized peptide as a template and designed an uncyclized analogue of this peptide that has antimicrobial activity. We focused on beta-hairpin-like structuring features. Improvements to the structure of this peptide reduced the activity of the peptide against gram-negative, Escherichia coli but improved the activity against gram-positive, Corynebacterium glutamicum. Distinctions in structuring effects on gram-negative versus gram-positive activity were also seen in a second peptide system. Structural improvements resulted in a peptide that was more active than the native against gram-positive bacterium but less active against gram-negative bacterium. Our results show that there is not always a correlation between improved hairpin-structuring and activity. Other factors such as the type of bacteria being targeted as well as net positive charge can play a role in the potency of AMPs. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd.

Antimicrobial Peptides of Meat Origin - An In silico and In vitro Analysis.

The aim of this study was to evaluate the antimicrobial activity of meat protein-derived peptides against selected Gram-positive and Gram-negative bacteria. The in silico and in vitro approach was combined to determine the potency of antimicrobial peptides derived from pig (Sus scrofa) and cow (Bos taurus) proteins. The in silico studies consisted of an analysis of the amino acid composition of peptides obtained from the CAMPR database, their molecular weight and other physicochemical properties (isoelectric point, molar extinction coefficient, instability index, aliphatic index, hydropathy index and net charge). The degree of similarity was estimated between the antimicrobial peptide sequences derived from the slaughtered animals and the main meat proteins. Antimicrobial activity of peptides isolated from dry-cured meat products was analysed (in vitro) against two strains of pathogenic bacteria using the disc diffusion method. There was no evidence of growthinhibitory properties of peptides isolated from dry-cured meat products against Escherichia coli K12 ATCC 10798 and Staphylococcus aureus ATCC 25923.

Antimicrobial Peptide Potency is Facilitated by Greater Conformational Flexibility when Binding to Gram-negative Bacterial Inner Membranes.

The interaction of antimicrobial peptides (AMPs) with the inner membrane of Gram-negative bacteria is a key determinant of their abilities to exert diverse bactericidal effects. Here we present a molecular level understanding of the initial target membrane interaction for two cationic α-helical AMPs that share structural similarities but have a ten-fold difference in antibacterial potency towards Gram-negative bacteria. The binding and insertion from solution of pleurocidin or magainin 2 to membranes representing the inner membrane of Gram-negative bacteria, comprising a mixture of 128 anionic and 384 zwitterionic lipids, is monitored over 100 ns in all atom molecular dynamics simulations. The effects of the membrane interaction on both the peptide and lipid constituents are considered and compared with new and published experimental data obtained in the steady state. While both magainin 2 and pleurocidin are capable of disrupting bacterial membranes, the greater potency of pleurocidin is linked to its ability to penetrate within the bacterial cell. We show that pleurocidin displays much greater conformational flexibility when compared with magainin 2, resists self-association at the membrane surface and penetrates further into the hydrophobic core of the lipid bilayer. Conformational flexibility is therefore revealed as a key feature required of apparently α-helical cationic AMPs for enhanced antibacterial potency.

Mechanical properties that influence antimicrobial peptide activity in lipid membranes.

Antimicrobial peptides are small amphiphilic proteins found in animals and plants as essential components of the innate immune system and whose function is to control bacterial infectious activity. In order to accomplish their function, antimicrobial peptides use different mechanisms of action which have been deeply studied in view of their potential exploitation to treat antibiotic-resistant bacterial infections. One of the main mechanisms of action of these peptides is the disruption of the bacterial membrane through pore formation, which, in some cases, takes place via a monomer to oligomer cooperative transition. Previous studies have shown that lipid composition, and the presence of exogenous components, such as cholesterol in model membranes or carotenoids in bacteria, can affect the potency of distinct antimicrobial peptides. At the same time, considering the membrane as a two-dimensional material, it has been shown that membrane composition defines its mechanical properties which might be relevant in many membrane-related processes. Nevertheless, the correlation between the mechanical properties of the membrane and antimicrobial peptide potency has not been considered according to the importance it deserves. The relevance of these mechanical properties in membrane deformation due to peptide insertion is reviewed here for different types of pores in order to elucidate if indeed membrane composition affects antimicrobial peptide activity by modulation of the mechanical properties of the membrane. This would also provide a better understanding of the mechanisms used by bacteria to overcome antimicrobial peptide activity.

Towards infection resistant surfaces: Polymer brush chemistry and peptide structure modulate the potency of antimicrobial peptides

Event Abstract Back to Event Towards infection resistant surfaces: Polymer brush chemistry and peptide structure modulate the potency of antimicrobial peptides Kai Yu1*, Joey Lo2*, Yan Mei1*, Evan Haney3*, Robert Hancock3*, Dirk Lange2* and Jayachandran Kizhakkedathu1* 1 University of British Columbia, Department of Pathology and lab Medicine & Centre for Blood Research, Canada 2 University of British Columbia, Department of Urologic Sciences, Canada 3 University of British Columbia, Department of Microbiology and Immunology, Canada Introduction: Implanted device associated bacterial infection greatly compromises the long-term performance and stability of the implant, and is associated with increased morbidity and mortality[1]. Antibacterial coatings based on immobilizing antimicrobial peptides (AMPs) into the polymer brush provide a robust anti-infection method which can not only prevent bacterial adhesion but also kill the adhered bacteria on the surface and prevent biofilm formation[2]. However, there is limited information available on how brush chemistry and structure contribute to the interaction of conjugated AMPs, and how these parameters influence the overall antimicrobial activity of the AMP conjugated surfaces. Thus, we investigated the influence of polymer brush chemistry and peptide structure on the antimicrobial activity of peptides conjugated to various polymer brush coated surfaces. Materials and Methods: Polymer brushes containing, DMA:N,N-dimethylacrylamide, MPC:2-methacryloyloxyethyl phosphorylcholine, MPDSAH:[3-(methacryloylamido)propyl)dimethyl(3-sulfopropyl)ammonium hydroxide), APMA: N-(3-Aminopropyl)methacrylamide, P(DMA-co-APMA), P(MPC-co-APMA) and P(MPDSAH-co-APMA), were generated on polystyrene nanoparticles (NPs) and titanium substrate by surface initiated atom transfer radical polymerization[3]. Two cathelicidin-derived peptides, E6 (RRWRIVVIRVRRC) or Tet20 (KRWRIRVRVIRKC), were conjugated to the brushes to construct different combinations of AMPs tethered polymer brush coating. The antimicrobial activity of surface tethered AMPs on three polymer brush systems against Gram-positive (S. aureus) and Gram-negative bacteria (E. coli and P. aeruginosa) was determined. Live/Dead BacLight bacterial viability kit was used to determine bacterial cell viability and adhesion on AMP-brush grafted substrate. Result and Discussion: The successful grafting polymer brushes onto the polystyrene NPs and conjugation of peptides were confirmed by FTIR spectra. The antimicrobial activity of tethered AMPs against E. coli was tested as a function of peptide concentration (Figure 1). As shown, E6 and Tet20 were more effective on PDMA brushes in comparison to PMPC or PMPDSAH brushes at similar AMP concentrations demonstrating the influence of polymer brush chemistry. The observed effect was confirmed for other bacterial species with different outer envelopes, specifically the Gram-positive S. aureus and Gram-negative P. aeruginosa. In addition, polymer brush tethered E6 was more active than tethered Tet20 at all peptide concentrations, confirming the importance of peptide sequence on the activity of tethered peptides. The influence of polymer brush chemistry on antimicrobial activity of tethered peptides and their anti-adhesion properties were further validated by using AMP-brush grafted Ti surface. Figure 2 shows the merged fluorescence images of live and dead bacteria on different polymer brush tethered E6 after incubating with S. aureus. The greater intensity of yellow color on E6 tethered PDMA brush indicated that the percentages of dead bacteria on this surface was much higher than that on E6 conjugated PMPC and PMPDSAH brushes. These results were corroborated with changes in peptide secondary structure analyzed by surface specific CD spectroscopy of AMP tethered brushes in presence of biomembranes. Conclusions: Our results show that the brush chemistry is an important parameter that determines the overall antimicrobial activity of surface conjugated AMPs. These results will have important implications in the design of novel infection-resistant coatings utilizing tethered AMP technology with potent antimicrobial and antifouling characteristics. This research was funded by the Canadian Institutes of Health Research (CIHR) and Natural Science and Engineering Research Council (NSERC) of Canada.

Toward Infection-Resistant Surfaces: Achieving High Antimicrobial Peptide Potency by Modulating the Functionality of Polymer Brush and Peptide.

Bacterial infection associated with indwelling medical devices and implants is a major clinical issue, and the prevention or treatment of such infections is challenging. Antimicrobial coatings offer a significant step toward addressing this important clinical problem. Antimicrobial coatings based on tethered antimicrobial peptides (AMPs) on hydrophilic polymer brushes have been shown to be one of the most promising strategies to avoid bacterial colonization and have demonstrated broad spectrum activity. Optimal combinations of the functionality of the polymer-brush-tethered AMPs are essential to maintaining long-term AMP activity on the surface. However, there is limited knowledge currently available on this topic. Here we report the development of potent antimicrobial coatings on implant surfaces by elucidating the roles of polymer brush chemistry and peptide structure on the overall antimicrobial activity of the coatings. We screened several combinations of polymer brush coatings and AMPs constructed on nanoparticles, titanium surfaces, and quartz slides on their antimicrobial activity and bacterial adhesion against Gram-positive and Gram-negative bacteria. Highly efficient killing of planktonic bacteria by the antimicrobial coatings on nanoparticle surfaces, as well as potent killing of adhered bacteria in the case of coatings on titanium surfaces, was observed. Remarkably, the antimicrobial activity of AMP-conjugated brush coatings demonstrated a clear dependence on the polymer brush chemistry and peptide structure, and optimization of these parameters is critical to achieving infection-resistant surfaces. By analyzing the interaction of polymer-brush-tethered AMPs with model lipid membranes using circular dichroism spectroscopy, we determined that the polymer brush chemistry has an influence on the extent of secondary structure change of tethered peptides before and after interaction with biomembranes. The peptide structure also has an influence on the density of conjugated peptides on polymer brush coatings and the resultant wettability of the coatings, and both of these factors contributed to the antimicrobial activity and bacterial adhesion of the coatings. Overall, this work highlights the importance of optimizing the functionality of the polymer brush to achieve infection-resistant surfaces and presents important insight into the design criteria for the selection of polymers and AMPs toward the development of potent antimicrobial coating on implants.

Susceptibility of Intracellular Coxiella burnetii to Antimicrobial Peptides in Mouse Fibroblast Cells

Q fever is a zoonotic disease caused by Coxiella burnetii, an obligate intracellular bacterium that resides inside a phagolysosome-like niche. Chronic Q fever is typified by endocarditis, and is treated with multiple antibiotics for at least 18 months. The discovery of clinical C. burnetii isolates resistant to the first-line antibiotic doxycycline, and the problematic nature of chronic Q fever treatment have demonstrated the need for improved treatment regimes. To search for alternative antimicrobial agents, we assessed the effect of 26 antimicrobial peptides (AMPs) on the intracellular growth of C. burnetii in L929 cells at a concentration of 25 µM or their maximal non-cytotoxic concentration. Among the peptides tested, A3-APO, Cath-BF, δ-Hemolysin, Octa-1, P5 and Pleurocidin were able to significantly reduce both the total bacterial cell number and the host cell bacterial burden (average bacterial number per host cell). Combining selected AMPs with Chariot, a non-covalent carrier peptide, did not increase treatment potency when non-cytotoxic concentrations were used, with the exception of P5, which remained active at a concentration of 1.6 µM (1.8 µg/mL). Combining AMPs with each other did not further improve AMP potency, with some treatment combinations increasing the growth rate of C. burnetii by >3-fold. This is the first description of AMP cellular penetration to exhibit inhibitory affect on intracellular C. burnetii growth. These results are the first step in the development of a non-traditional antibiotic treatment for Q fever.