Lipopolysaccharide Neutralization by Cationic-Amphiphilic Polymers through Pseudoaggregate Formation

Structure optimizing of flavonoids against both MRSA and VRE

Methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococci (VRE) cause more than 100,000 deaths each year, which need efficient and non-resistant antibacterial agents. SAR analysis of 162 flavonoids from the plant in this paper suggested that lipophilic group at C-3 was crucial, and then 63 novel flavonoid derivatives were designed and total synthesized. Among them, the most promising K15 displayed potent bactericidal activity against clinically isolated MRSA and VRE (MICs = 0.25-1.00 μg/mL) with low toxicity and high membrane selectivity. Moreover, mechanism insights revealed that K15 avoided resistance by disrupting biofilm and targeting the membrane, while vancomycin caused 256 times resistance against MRSA, and ampicillin caused 16 times resistance against VRE by the same 20 generations inducing. K15 eliminated residual bacteria in mice skin MRSA-infected model (>99 %) and abdominal VRE-infected model (>92 %), which was superior to vancomycin and ampicillin.

Amphiphilic Dendrimer as Potent Antibacterial against Drug-Resistant Bacteria in Mouse Models of Human Infectious Diseases

Modern medicine continues to struggle against antibiotic-resistant bacterial pathogens. Among the pathogens of critical concerns are the multidrug-resistant (MDR) Pseudomonas aeruginosa, Staphylococcus aureus, and Klebsiella pneumoniae. These pathogens are major causes of nosocomial infections among immunocompromised individuals, involving major organs such as lung, skin, spleen, kidney, liver, and bloodstream. Therefore, novel approaches are direly needed. Recently, we developed an amphiphilic dendrimer DDC18-8A exhibiting high antibacterial and antibiofilm efficacy in vitro. DDC18-8A is composed of a long hydrophobic alkyl chain and a small hydrophilic poly(amidoamine) dendron bearing amine terminals, exerting its antibacterial activity by attaching and inserting itself into bacterial membranes to trigger cell lysis. Here, we examined the pharmacokinetics and in vivo toxicity as well as the antibacterial efficacy of DDC18-8A in mouse models of human infectious diseases. Remarkably, DDC18-8A significantly reduced the bacterial burden in mouse models of acute pneumonia and bacteremia by P. aeruginosa, methicillin-resistant S. aureus (MRSA), and carbapenem-resistant K. pneumoniae and neutropenic soft tissue infection by P. aeruginosa and MRSA. Most importantly, DDC18-8A outperformed pathogen-specific antibiotics against all three pathogens by achieving a similar bacterial clearance at 10-fold lower therapeutic concentrations. In addition, it showed superior stability and biodistribution in vivo, with excellent safety profiles yet without any observable abnormalities in histopathological analysis of major organs, blood serum biochemistry, and hematology. Collectively, we provide strong evidence that DDC18-8A is a promising alternative to the currently prescribed antibiotics in addressing challenges associated with nosocomial infections by MDR pathogens.

Dual functional therapeutics: mitigating bacterial infection and associated inflammation

The emergence of antimicrobial resistance, coupled with the occurrence of persistent systemic infections, has already complicated clinical therapy efforts. Moreover, infections are also accompanied by strong inflammatory responses, generated by the host's innate and adaptive immune systems. The closely intertwined relationship between bacterial infection and inflammation has multiple implications on the ability of antibacterial therapeutics to tackle infection and inflammation. Particularly, uncontrolled inflammatory responses to infection can lead to sepsis, a life-threatening physiological condition. In this review, we discuss dual-functional antibacterial therapeutics that have potential to be developed for treating inflammation associated with bacterial infections. Immense research is underway that aims to develop new therapeutic agents that, when administered, regulate the excess inflammatory response, i.e. they have immunomodulatory properties along with the desired antibacterial activity. The classes of antibiotics that have immunomodulatory function in addition to antibacterial activity have been reviewed. Host defense peptides and their synthetic mimics are amongst the most sought-after solutions to develop such dual-functional therapeutics. This review also highlights the important classes of peptidomimetics that exhibit both antibacterial and immunomodulatory properties.

Antibacterial peptides-loaded bioactive materials for the treatment of bone infection

Bacterial bone infection in open fractures is an urgent problem to solve in orthopedics. Antimicrobial peptides (AMPs), as a part of innate immune defense, have good biocompatibility. Their antibacterial mechanism and therapeutic application against bacteria have been widely studied. Compared with traditional antibiotics, AMPs do not easily cause bacterial resistance and can be a reliable substitute for antibiotics in the future. Therefore, various physical and chemical strategies have been developed for the combined application of AMPs and bioactive materials to infected sites, which are conducive to maintaining the local stability of AMPs, reducing many complications, and facilitating bone infection resolution. This review explored the molecular structure, function, and direct and indirect antibacterial mechanisms of AMPs, introduced two important AMPs (LL-37 and β-defensins) in bone tissues, and reviewed advanced AMP loading strategies and different bioactive materials. Finally, the latest progress and future development of AMPs-loaded bioactive materials for the promotion of bone infection repair were discussed. This study provided a theoretical basis and application strategy for the treatment of bone infection with AMP-loaded bioactive materials.

Mechanically robust and highly bactericidal macroporous polymeric gels based on quaternized N,N-(dimethylamino)ethyl methacrylate possessing varying alkyl chain lengths

In this paper, macroporous antimicrobial polymeric gels (MAPGs) functionalized with active quaternary ammonium cations attached to varying hydrocarbon chain lengths have been fabricated. Apart from the change in the alkyl chain length attached to the quaternary ammonium cation, the amount of crosslinker was also varied during the fabrication of the macroporous gels. The prepared gels were characterized using Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, field emission scanning electron microscopy (FE-SEM) and swelling studies. In addition, the mechanical properties of the fabricated macroporous gels were studied using compression and tensile testing. The antimicrobial activity of the gels has been determined for Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa) as well as Gram-positive bacteria (Bacillus subtilis, Staphylococcus aureus). Antimicrobial activity, as well as the mechanical properties of the macroporous gels, was found to be influenced by the alkyl chain length attached to the quaternary ammonium cations as well as by the amount of crosslinker used for the fabrication of the gel. In addition, on increasing the alkyl chain length from C4 (butyl) to C8 (octyl), the effectiveness of the polymeric gels increased. It was observed that the gels derived using a tertiary amine (NMe₂) containing monomer showed relatively low antimicrobial activity as compared to the gels obtained using quaternized monomers (C4 (butyl), C6 (hexyl), and C8 (octyl)). The gels based on the quaternized C8 monomer displayed the highest antimicrobial activity and mechanical stability as compared to the gels based on the C4 and C6 monomers.

Facial amphiphilicity index correlating chemical structures with antimicrobial efficacy

Facial amphiphilicity is an extraordinary chemical structure feature of a variety of antimicrobial peptides and polymers. Vast efforts have been dedicated to small molecular, macromolecular and dendrimer-like systems to mimic this highly preferred structure or conformation, including local facial amphiphilicity and global amphiphilicity. This work conceptualizes Facial Amphiphilicity Index (FAI) as a numerical value to quantitatively characterize the measure of chemical compositions and structural features in dictating antimicrobial efficacy. FAI is a ratio of numbers of charges to rings, representing both compositions of hydrophilicity and hydrophobicity. Cationic derivatives of multicyclic compounds were evaluated as model systems for testing antimicrobial selectivity against Gram-negative and Gram-positive bacteria. Both monocyclic and bicyclic compounds are non-antimicrobial regardless of FAIs. Antimicrobial efficacy was observed with systems having larger cross-sectional areas including tricyclic abietic acid and tetracyclic bile acid. While low and high FAIs respectively lead to higher and lower antimicrobial efficacy, in consideration of cytotoxicity, the sweet spot is typically suited with intermediate FAIs for each specific system. This can be well explained by the synergistic hydrophobic-hydrophobic and electrostatic interactions with bacterial cell membranes and the difference between bacterial and mammalian cell membranes. The adoption of FAI would pave a new avenue toward the design of next-generation antimicrobial macromolecules and peptides.

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Established a numerical index to quantify the effect of facial amphiphilicity on antimicrobial efficacy.

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Evaluated the facial amphiphilicity index of multicyclic compounds possessing various rings and cationic charges.

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Provided this index a new tool toward more quantitative designs of AMP mimics.

Designed symmetrical β-hairpin peptides for treating multidrug-resistant salmonella typhimurium infections

The rapid emergence and prevalence of multidrug-resistant salmonellosis lack effective therapies, which causes epidemic health problems and stimulates the development of antimicrobials with novel modes of action. In this research, 10 short symmetrical β-hairpin peptides are synthesized by combining the β-turn of Leucocin-A with recurring hydrophobic and cationic amino acid sequences. Those designed peptides exhibited potent antibacterial activities against drug-susceptible and drug-resistant Salmonella. One of the 10 peptides, WK2 ((WK)₂CTKSGC(KW)₂), displayed best cell selectivity towards Salmonella cells over macrophages and erythrocytes in a co-culture model. Fluorescent measurements and microscopic observations reflected that WK2 exerted its antimicrobial activity through a membrane-lytic mechanism. Moreover, the β-hairpin peptides can bind to endotoxin (LPS) and suppress the production of LPS-induced proinflammatory cytokines in RAW264.7 cells, indicating as a potent anti-inflammatory activity. The preliminary in vivo studies can also demonstrate that WK2 decreased loads of Salmonella in the liver and spleen, mitigated Salmonella-caused inflammation and maintained the integrity of intestinal mucosal surfaces. Ultimately, the results highlight that WK2 is a promising therapeutic agent to prevent multidrug-resistant S. Typhimurium infections in humans and animals.

Smart Multifunctional Polymer Systems as Alternatives or Supplements of Antibiotics To Overcome Bacterial Resistance

In recent years, infectious diseases have again become a critical threat to global public health largely due to the challenges posed by antimicrobial resistance. Conventional antibiotics have played a crucial role in combating bacterial infections; however, their efficacy is significantly impaired by widespread drug resistance. Natural antimicrobial peptides (AMPs) and their polymeric mimics demonstrate great potential for killing bacteria with low propensity of resistance as they target the microbial membrane rather than a specific molecular target, but they are also toxic to the host eukaryotic cells. To minimize antibiotics systemic spread and the required dose that promote resistance and to advocate practical realization of the promising activity of AMPs and polymers, smart systems to target bacteria are highly sought after. This review presents bacterial recognition by various specific targeting molecules and the delivery systems of active components in supramolecules. Bacteria-induced activations of antimicrobial-based nanoformulations are also included. Recent advances in the bacteria targeting and delivery of synthetic antimicrobial agents may assist in developing new classes of highly selective antimicrobial systems which can improve bactericidal efficacy and greatly minimize the spread of bacterial resistance.

Polymeric Biomaterials for Prevention and Therapeutic Intervention of Microbial Infections

The escalating emergence of multidrug-resistant (MDR) pathogens and their ability to colonize into biofilms on a multitude of surfaces have struck global health as a nightmare. The stagnation in the development of antibiotics and the deterioration of clinical pipelines have incited an invigorating search for smart and innovative alternatives in the scientific community. Further, a steep rise in the usage of biomedical devices and implants has resulted in an accelerated occurrence of infections. Toward the goal of mitigation of the aforementioned challenges, antimicrobial polymers have stood out as an astounding option. In this perspective, we highlight our contribution to the field of polymeric biomaterials for tackling antimicrobial resistance (AMR) and infections. Polymers inspired from antimicrobial peptides (AMPs) have been utilized as therapeutic interventions to curb MDR infections and also to rejuvenate obsolete antibiotics. Further, cationic polymers have been used to impart antimicrobial properties to different biomedical surfaces. These cationic polymer-coated surfaces can inactivate pathogens upon contact as well as prevent their biofilm formation. In addition, antimicrobial hydrogels, which are prepared from either inherently antimicrobial polymers or biocide-loaded polymeric hydrogel matrices, have also been engineered. With a brief overview of the progress in the field, detailed elaboration of the polymeric biomaterials for prevention and therapeutic intervention of microbial infections developed by our group is presented. Finally, the challenges in the field of antimicrobial polymers with discussion on the proceedings of polymeric research to alleviate these challenges are discussed.

Adsorption-Based Detoxification of Endotoxins by Porous Flexible Organic Frameworks

Bacterial lipopolysaccharides (LPS, endotoxins) cause sepsis that is responsible for a huge amount of mortality globally. However, their neutralization or detoxification remains an unmet medical need. We envisaged that cationic organic frameworks with persistent hydrophobic porosity may adsorb and thus neutralize LPS through a combination of cooperative ion-pairing electrostatic attraction and hydrophobicity. We here report the preparation of two water-soluble flexible organic frameworks (FOF-1 and FOF-2) from tetratopic and ditopic precursors through quantitative formation of hydrazone bonds at room temperature. The two FOFs are revealed to possess hydrodynamic diameters, which range from 20 to 120 nm, depending on the concentrations. Dynamic light scattering and isothermal titration calorimetric and chromogenic limulus amebocyte lysate experiments indicate that both frameworks are able to adsorb and thus reduce the concentration of free LPS molecules in aqueous solution, whereas cytokine inhibition experiments with RAW264.7 support that this adsorption can significantly decrease the toxicity of LPS. In vivo experiments with mice (five males per group) show that the injection of FOF-1 at a dose of 0.6 mg/kg realizes the survival of all of the mice administrated with LPS of the d-galactosamine (d-Gal)-sensitized absolute lethal dose (LD₁₀₀, 0.05 mg/kg), whereas its maximum tolerated dose for mice is determined to be 10 mg/kg. These findings provide a new promising sequestration strategy for the development of porous agents for the neutralization of LPS.

The Role of Lipopolysaccharide-Induced Cell Signalling in Chronic Inflammation

Lipopolysaccharide (LPS) is the main structural component of the outer membrane of most Gram-negative bacteria and has diverse immunostimulatory and procoagulant effects. Even though LPS is well described for its role in the pathology of sepsis, considerable evidence demonstrates that LPS-induced signalling and immune dysregulation are also relevant in the pathophysiology of many diseases, characteristically where endotoxaemia is less severe. These diseases are typically chronic and progressive in nature and span broad classifications, including neurodegenerative, metabolic, and cardiovascular diseases. This Review reappraises the mechanisms of LPS-induced signalling and emphasises the crucial contribution of LPS to the pathology of multiple chronic diseases, beyond conventional sepsis. This perspective asserts that new ways of approaching chronic diseases by targeting LPS-driven pathways may be of therapeutic benefit in a wide range of chronic inflammatory conditions.

Mechanism of Antimicrobial Peptides: Antimicrobial, Anti-Inflammatory and Antibiofilm Activities

Antimicrobial peptides (AMPs) are regarded as a new generation of antibiotics. Besides antimicrobial activity, AMPs also have antibiofilm, immune-regulatory, and other activities. Exploring the mechanism of action of AMPs may help in the modification and development of AMPs. Many studies were conducted on the mechanism of AMPs. The present review mainly summarizes the research status on the antimicrobial, anti-inflammatory, and antibiofilm properties of AMPs. This study not only describes the mechanism of cell wall action and membrane-targeting action but also includes the transmembrane mechanism of intracellular action and intracellular action targets. It also discusses the dual mechanism of action reported by a large number of investigations. Antibiofilm and anti-inflammatory mechanisms were described based on the formation of biofilms and inflammation. This study aims to provide a comprehensive review of the multiple activities and coordination of AMPs in vivo, and to fully understand AMPs to realize their therapeutic prospect.

Microbiota-gut-brain axis and Alzheimer's disease: Implications of the blood-brain barrier as an intervention target

The microbiota-gut-brain axis has emerged as a focal point of biomedical research. Alterations of gut microbiota are involved in not only various immune/inflammatory disorders but also neurological disorders including Alzheimer's disease (AD). The initial stage of the involvement of gut microbiota in the pathogenesis of AD may be the dysfunction of the blood-brain barrier (BBB). Gut microbiota-derived products in the circulation can worsen the BBB integrity, easily cross the disrupted BBB and enter the brain to promote pathological changes in AD. In this review, we first summarize the current evidence of the associations among gut microbiota, AD, and BBB integrity. We then discuss the mechanism of gut microbiota on BBB dysfunction with a focus on bacteria-derived lipopolysaccharide and exosomal high-mobility group box 1. Novel insights into the modification of the BBB as an intervention approach for AD are highlighted as well.

Macromolecular Nanotherapeutics and Antibiotic Adjuvants to Tackle Bacterial and Fungal Infections

The escalating rise in the population of multidrug-resistant (MDR) pathogens coupled with their biofilm forming ability has struck the global health as nightmare. Alongwith the threat of aforementioned menace, the sluggish development of new antibiotics and the continuous deterioration of the antibiotic pipeline has stimulated the scientific community toward the search of smart and innovative alternatives. In near future, membrane targeting antimicrobial polymers, inspired from antimicrobial peptides, can stand out significantly to combat against the MDR superbugs. Many of these amphiphilic polymers can form nanoaggregates through self-assembly with superior and selective antimicrobial efficacy. Additionally, these macromolecular nanoaggregrates can be utilized to engineer smart antibiotic-delivery system for on-demand drug-release, exploiting the infection site's micoenvironment. This strategy substantially increases the local concentration of antibiotics and reduces the associated off-target toxicity. Furthermore, amphiphilc macromolecules can be utilized to rejuvinate obsolete antibiotics to tackle the drug-resistant infections. This review article highlights the recent developments in macromolecular architecture to design numerous nanostructures with broad-spectrum antimicrobial activity, their application in fabricating smart drug delivery systems and their efficacy as antibiotic adjuvants to circumvent antimicrobial resistance. Finally, the current challenges and future prospects are briefly discussed for further exploration and their practical application in clinical settings.

Cathelicidin and PMB neutralize endotoxins by multifactorial mechanisms including LPS interaction and targeting of host cell membranes

Antimicrobial peptides (AMPs) contribute to an effective protection against infections. The antibacterial function of AMPs depends on their interactions with microbial membranes and lipids, such as lipopolysaccharide (LPS; endotoxin). Hyperinflammation induced by endotoxin is a key factor in bacterial sepsis and many other human diseases. Here, we provide a comprehensive profile of peptide-mediated LPS neutralization by systematic analysis of the effects of a set of AMPs and the peptide antibiotic polymyxin B (PMB) on the physicochemistry of endotoxin, macrophage activation, and lethality in mice. Mechanistic studies revealed that the host defense peptide LL-32 and PMB each reduce LPS-mediated activation also via a direct interaction of the peptides with the host cell. As a biophysical basis, we demonstrate modifications of the structure of cholesterol-rich membrane domains and the association of glycosylphosphatidylinositol (GPI)-anchored proteins. Our discovery of a host cell-directed mechanism of immune control contributes an important aspect in the development and therapeutic use of AMPs.

A Novel Targeted Therapy System for Cervical Cancer: Co-Delivery System of Antisense LncRNA of MDC1 and Oxaliplatin Magnetic Thermosensitive Cationic Liposome Drug Carrier

BACKGROUND

This study was aimed to prepare a novel magnetic thermosensitive cationic liposome drug carrier for the codelivery of Oxaliplatin (OXA) and antisense lncRNA of MDC1 (MDC1-AS) to Cervical cancer cells and evaluate the efficiency of this drug carrier and its antitumor effects on Cervical cancer.

METHODS

Thermosensitive magnetic cationic liposomes were prepared using thin-film hydration method. The OXA and MDC1-AS vectors were loaded into the codelivery system, and the in vitro OXA thermosensitive release activity, efficiency of MDC1-AS regulating MDC1, in vitro cytotoxicity, and in vivo antitumor activity were determined.

RESULTS

The codelivery system had desirable targeted delivery efficacy, OXA thermosensitive release, and MDC1-AS regulating MDC1. Codelivery of OXA and MDC1-AS enhanced the inhibition of cervical cancer cell growth in vitro and in vivo, compared with single drug delivery.

CONCLUSION

The novel codelivery of OXA and MDC1-AS magnetic thermosensitive cationic liposome drug carrier can be applied in the combined chemotherapy and gene therapy for cervical cancer.

Aggregation Behavior, Antibacterial Activity and Biocompatibility of Catanionic Assemblies Based on Amino Acid-Derived Surfactants

The surface activity, aggregates morphology, size and charge characteristics of binary catanionic mixtures containing a cationic amino acid-derived surfactant N(π), N(τ)-bis(methyl)-L-Histidine tetradecyl amide (DMHNHC₁₄) and an anionic surfactant (the lysine-based surfactant N^α-lauroyl-N^εacetyl lysine (C₁₂C₃L) or sodium myristate) were investigated for the first time. The cationic surfactant has an acid proton which shows a strong pK_a shift irrespective of aggregation. The resulting catanionic mixtures exhibited high surface activity and low critical aggregation concentration as compared with the pure constituents. Catanionic vesicles based on DMHNHC₁₄/sodium myristate showed a monodisperse population of medium-size aggregates and good storage stability. According to Small-Angle X-Ray Scattering (SAXS), the characteristics of the bilayers did not depend strongly on the system composition for the positively charged vesicles. Negatively charged vesicles (cationic surfactant:myristate ratio below 1:2) had similar bilayer composition but tended to aggregate. The DMHNHC₁₄-rich vesicles exhibited good antibacterial activity against Gram-positive bacteria and their bactericidal effectivity declined with the decrease of the cationic surfactant content in the mixtures. The hemolytic activity and cytotoxicity of these catanionic formulations against non-tumoral (3T3, HaCaT) and tumoral (HeLa, A431) cell lines also improved by increasing the ratio of cationic surfactant in the mixture. These results indicate that the biological activity of these systems is mainly governed by the cationic charge density, which can be modulated by changing the cationic/anionic surfactant ratio in the mixtures. Remarkably, the incorporation of cholesterol in those catanionic vesicles reduces their cytotoxicity and increases the safety of future biomedical applications of these systems.

An update on endotoxin neutralization strategies in Gram-negative bacterial infections

INTRODUCTION

Gram-negative bacterial infections represent still a severe problem of human health care, regarding the increase in multi-resistance against classical antibiotics and the lack of newly developed antimicrobials. For the fight against these germs, anti-infective agents must overcome and/or bind to the Gram-negative outer membrane consisting of a lipopolysaccharide (LPS, endotoxin) outer leaflet and an inner leaflet from phospholipids, with additional peripheral or integral membrane proteins (OMP's).

AREAS COVERED

The current article reviews data of existing therapeutic options and summarizes newer approaches for targeting and neutralizing endotoxins, ranging from in vitro over in vivo animal data to clinical applications by using databases such as Medline.

EXPERT OPINION

Conventional antibiotic treatment of the bacteria leads to their killing, but not necessary LPS neutralization, which may be a severe problem in particular for the systemic pathway. This is the reason why there is an increasing number of therapeutic approaches, which - besides combating whole bacteria - at the same time try to neutralize endotoxin within or outside the bacterial cells mainly responsible for the high inflammation induction in Gram-negative species.

Insights into electrochemical decomposition mechanism of lipopolysaccharide using TiO2 nanotubes arrays electrode

Electrochemical decomposition of lipopolysaccharide (LPS) was firstly investigated over titania nanotubes (TNTs) arrays electrode. The TNTs layer of this electrode consisted of numerous tubular structures which arranged tightly, and the average diameter of each nanotube is 100 ± 5 nm. The degradation of LPS and polysaccharides followed pseudo-first-order kinetics. The optimal LPS removal ratio was nearly 80 %. The endotoxin toxicity of LPS steadily decreased during the electrolysis process. The acute toxicity of the intermediates increased suddenly at the beginning of electrochemical degradation process (< 5 min), then maintained high inhibition ratio (> 95 %) for about 150 min, and decreased significantly (< 10 %) after electrolysis for 240 min. After 20 min of electrolysis, LPS with molecular weight of 116,854 Da was transformed into small molecular compounds with molecular weights of 59,312 - 12,209 Da. Possible degradation and detoxification mechanisms of LPS including electric-field-force-driving accumulation, adsorption and direct electron transfer on TNTs arrays electrode, and •OH oxidation were proposed. This study underscores that electrochemical technique can be applied to eliminate and decrease the toxicity of LPS from contaminated water.

Effect of sodium deoxycholate sulfate on outer membrane permeability and neutralization of bacterial lipopolysaccharides by polymyxin B formulations

We demonstrated binding interactions of polymyxin B (PMB), PMB formulations in the mole ratios of 1:2 and 1:3 of PMB:sodium deoxycholate sulfate (SDCS) and a commercial PMB formulation (CPMB) with lipopolysaccharides (LPS). The 1:2 PMB formulation (78.5-135.2 nM) exhibited a lower number of binding sites to the tested LPS compared to CPMB (112.6-140.9 nM) whereas 1:3 PMB formulation exhibited a higher number of binding sites (143.9-340.2 nM). Similarly, in the presence of LPS, the 1:2 PMB formulation (163.8-221.4 nm) exhibited smaller particle sizes compared to PMB, CPMB and 1:3 PMB formulation (248.8-603.5 nm). Molecular docking simulation suggested that the fatty acyl tails of LPS wrap together to produce a pseudo-globular structure of PMB-LPS complex, and among those 1:2 PMB formulation formed a more stable structure. The primary forces behind this complex are hydrogen bonds and salt bridges among the LPS, PMB, and SDCS. This study revealed that the PMB, CPMB, and PMB formulations inserted into the LPS micelles to disrupt the LPS membrane, whereas the SDCS may induce aggregation. The 1:2 PMB formulation also had higher bacterial uptake than other PMB formulations. The 1:2 PMB formulation neutralized the LPS micelles and was effective against Escherichia coli and Pseudomonas aeruginosa.

Nanosphere-shaped ammonio methacrylate copolymers: converting a pharmaceutical inactive ingredient to efficient therapeutics for experimental colitis

Inflammatory bowel disease (IBD) refers to progressive inflammatory disorders that impair the gastrointestinal tract's structure and function. Given their selective accumulation in inflamed tissues, nanoparticles are promising drug delivery systems for IBD treatment. The hypothesis here was that drug-free nanoscaled cationic ammonio methacrylate copolymers (AMCNP) may have a beneficial therapeutic effect in murine TNBS-induced colitis. Type A and B AMCNP (RLNP and RSNP, respectively) were prepared and characterized in vitro, and were rectally administered in two concentrations (5 and 25 mg ml^-1) for the treatment of two grades of murine experimental colitis. The impact of the nanoparticles upon the inflammatory markers, circulating LPS, intestinal permeability and colonic leukocyte populations was examined. Both RLNP and RSNP led to a significant mitigation of mild to moderate experimental colitis, as evident from the substantial reduction of myeloperoxidase (MPO) and alkaline phosphatase (AP) activities (more than two-fold, P < 0.05) and various pro-inflammatory cytokine concentrations (TNF-α, IL-1β, IL-6, IL-12). The best therapeutic efficiency was observed when the particles were used at 5 mg ml^-1, while the more cationic RLNP performed superior. When used against a severe grade of colitis, RLNP (5 mg ml^-1) resulted in a significant decrease of tissue MPO and TNF-α. It was found that treatment with AMCNP resulted in significant intestinal immune cell depletion, intestinal barrier function improvement, and 1.5-2.5 times reduction of the systemic endotoxin concentration. These findings highlighted the fact that nanoscaling endows the cationic amphiphilic AMCs unique therapeutic properties, which help mitigate murine experimental colitis in the absence of any drug load. The results also provided a glimpse of possible underlying mechanisms through which nanoscaled AMCs might have exerted their therapeutic effect within this context.

Interactions between Mutant Bacterial Lipopolysaccharide (LPS-Ra) Surface Layers: Surface Vesicles, Membrane Fusion, and Effect of Ca2+and Temperature

Lipopolysaccharides (LPS) are a major component of the protective outer membrane of Gram-negative bacteria. Understanding how the solution conditions may affect LPS-containing membranes is important to optimizing the design of antibacterial agents (ABAs) which exploit electrostatic and hydrophobic interactions to disrupt the bacteria membrane. Here, interactions between surface layers of LPS (Ra mutants) in aqueous media have been studied using a surface force apparatus (SFA), exploring the effects of temperature and divalent Ca²⁺ cations. Complementary dynamic light scattering (DLS) characterization suggests that vesicle-like aggregates of diameter ∼28-80 nm are formed by LPS-Ra in aqueous media. SFA results show that LPS-Ra vesicles adsorb weakly onto mica in pure water at room temperature (RT) and the surface layers are readily squeezed out as the two surfaces approach each other. However, upon addition of calcium (Ca²⁺) cations at near physiological concentration (2.5 mM) at RT, LPS multilayers or deformed LPS liposomes on mica are observed, presumably due to bridging between LPS phosphate groups and between LPS phosphates and negatively charged mica mediated by Ca²⁺, with a hard wall repulsion at surface separation D₀ ∼ 30-40 nm. At 40 °C, which is above the LPS-Ra β-α acyl chain melting temperature (T_m = 36 °C), fusion events between the surface layers under compression could be observed, evident from δD ∼ 8-10 nm steps in the force-distance profiles attributed to LPS-bilayers being squeezed out due to enhanced fluidity of the LPS acyl-chain, with a final hard wall surface separation D₀ ∼ 8-10 nm corresponding to the thickness of a single bilayer confined between the surfaces. These unprecedented SFA results reveal intricate structural responses of LPS surface layers to temperature and Ca²⁺, with implications to our fundamental understanding of the structures and interactions of bacterial membranes.

Amino Acid Conjugated Polymers: Antibacterial Agents Effective against Drug-Resistant Acinetobacter baumannii with No Detectable Resistance

An optimum hydrophilic/hydrophobic balance has been recognized as a crucial parameter in designing cationic polymers that mimic antimicrobial peptides (AMPs). To date, this balance was achieved either by hydrophilicity variation through altering the nature and the number of cationic charges or by hydrophobicity modulation through incorporation of alkyl groups of different chain lengths. However, how the hydrophobicity variation through AMPs' building blocks-amino acids-influences the antibacterial efficacy of AMP-mimicking cationic polymers has rarely been explored. Toward this goal, herein we report a class of amino acid conjugated polymers (ACPs) with tunable antibacterial activity through a simple post-polymer-functionalization strategy. Our polymeric design comprised a permanent cationic charge in every repeating unit, whereby the hydrophobicity was tuned through incorporation of different amino acids. Our results revealed that the amino acid alteration has a strong influence on antibacterial efficacy. Upon increasing the amino acid side-chain hydrophobicity, both the antibacterial activity (against broad spectrum of bacteria) and toxicity increased. However, the distinct feature of this class of polymers was their good activity against Acinetobacter baumannii-the top most critical pathogen according to WHO, which has created an alarming situation worldwide, causing the majority of infections in humans. A nontoxic (no hemolysis even at 1000 μg/mL) ACP including a glycine residue (ACP-1 (Gly)) showed very good activity (MIC = 8-16 μg/mL) against both drug-sensitive and drug-resistant strains of A. baumannii, including clinical isolates. This polymer not only was rapidly bactericidal against growing planktonic A. baumannii but also killed nondividing stationary-phase cells instantaneously (<2 min). Moreover, it eradicated the established biofilm formed by drug-resistant A. baumannii clinical isolates. No propensity for bacterial resistance development against this polymer was seen even after 14 continuous passages. Taken together, the results highlight that hydrophobicity modulation through incorporation of amino acids in cationic polymers will provide a significant opportunity in designing new ACPs with potent antibacterial activity and minimum toxicity toward mammalian cells. More importantly, the excellent anti-A. baumannii efficacy of the optimized lead polymer indicates its immense potential for being developed as therapeutic agent.

More QACs, more questions: Recent advances in structure activity relationships and hurdles in understanding resistance mechanisms

Quaternary ammonium compounds (QACs) are a class of antimicrobials that have been around for over a century; nevertheless, they have found continued renewal in the structures to which they can be appended. Ranging from antimicrobial polymers to adding novel modes of action to existing antibiotics, QACs have found ongoing use due to their potent properties. However, resistance against QACs has begun to emerge, and the mechanism of resistance is still only partially understood. In this review, we aim to summarize the current state of the field and what is known about the mechanisms of resistance so that the QACs of the future can be designed to be evermore efficacious and utilized to unearth the remaining mysteries that surround bacteria's resistance to them.

Comparative Structure-Activity Analysis of the Antimicrobial Activity, Cytotoxicity, and Mechanism of Action of the Fungal Cyclohexadepsipeptides Enniatins and Beauvericin

Filamentous fungi, although producing noxious molecules such as mycotoxins, have been used to produce numerous drugs active against human diseases such as paclitaxel, statins, and penicillin, saving millions of human lives. Cyclodepsipeptides are fungal molecules with potentially adverse and positive effects. Although these peptides are not novel, comparative studies of their antimicrobial activity, toxicity, and mechanism of action are still to be identified. In this study, the fungal cyclohexadepsipeptides enniatin (ENN) and beauvericin (BEA) were assessed to determine their antimicrobial activity and cytotoxicity against human cells. Results showed that these peptides were active against Gram-positive bacteria, Mycobacterium, and fungi, but not against Gram-negative bacteria. ENN and BEA had a limited hemolytic effect, yet were found to be toxic at low doses to nucleated human cells. Both peptides also interacted with bacterial lipids, causing low to no membrane permeabilization, but induced membrane depolarization and inhibition of macromolecules synthesis. The structure-activity analysis showed that the chemical nature of the side chains present on ENN and BEA (either iso-propyl, sec-butyl, or phenylmethyl) impacts their interaction with lipids, antimicrobial action, and toxicity.

Protective Action of Linear Polyethylenimine against Staphylococcus aureus Colonization and Exaggerated Inflammation in Vitro and in Vivo

Increased evolution of multidrug resistant pathogens necessitates the development of multifunctional antimicrobials. There is a perceived need for developing new antimicrobials that can interfere with acute inflammation after bacterial infections. Here, we investigated the therapeutic potential of linear polyethylenimine (LPEI) in vitro and in vivo. The minimum inhibitory concentration of LPEI ranged from 8 to 32 μg/mL and elicited rapid bactericidal activity against clinical isolates of meticillin-resistant Staphylococcus aureus (MRSA). The polymer was biocompatible for human cultured ocular and dermal cells. Prophylactic addition of LPEI inhibited the bacterial colonization of human primary dermal fibroblasts (hDFs). In a scratch wound cell migration assay, LPEI attenuated the migration inhibitory effects of bacterial secretions. The polymer neutralized the cytokine release by hDFs exposed to bacterial secretions, possibly by blocking their accessibility to host cell receptors. Topical instillation of LPEI (1 mg/mL) was noncytotoxic and did not affect the re-epithelialization of injured porcine cornea. In a prophylactic in vivo model of S. aureus keratitis, LPEI was superior to gatifloxacin in terms of reducing stimulation of cytokines, corneal edema, and overall severity of the infection. These observations demonstrate therapeutic potential of LPEI for antimicrobial prophylaxis.

Binding interactions of bacterial lipopolysaccharides to polymyxin B in an amphiphilic carrier 'sodium deoxycholate sulfate'

This work presents the outcomes of a comparative study of molecular interactions of polymyxin B (PMB) and F12 and F13 formulations in the mole ratios of 1:2 and 1:3 of PMB:sodium deoxycholate sulfate (SDCS), respectively, and a commercial PMB formulation (CPMB) with lipopolysaccharides (LPS). Several spectroscopic and interfacial studies were performed to obtain LPS-peptide interactions at a molecular level. The fluorescence titrimetry method revealed that the F12 formulation (325 nM) exhibited a lower number of binding sites to the LPS compared to CPMB and F13 as well as PMB alone (537 nM). Similarly, in the presence of LPS, the F12 formulation (88 nm) exhibited smaller particle sizes in the dynamic light scattering study compared to PMB (116 nm), CPMB, and the F13 formulation. An interfacial study and circular dichroism spectroscopy revealed PMB and CPMB insertion into the LPS micelles to destabilize and disrupt the LPS membrane, whereas the F12 and F13 formulations may induce pseudo-aggregation. The NMR and IR studies showed that the presence of SDCS, the hydrophobicity of PMB increased by hydrogen bonding and electrostatic interactions and formed stabilized PMB-SDCS micelles. The PMB-SDCS formulation is likely to release PMB for easy penetration into the lipid membrane and cause disruption of the complex LPS micelles. Furthermore, the PMB-SDCS formulations neutralized and detoxified the LPS micelles with minimal toxicity to normal kidney tubular cells as well as an immortalised kidney cell line. The antimicrobial properties of PMBloaded SDCS nanomicelles were effective against a resistant strain of Pseudomonas aeruginosa.

Distinct Intramolecular Hydrogen Bonding Dictates Antimicrobial Action of Membrane-Targeting Amphiphiles

As mechanisms underpinning the molecular interactions between membrane-targeting antimicrobials and Gram-negative bacterial membranes at atomistic scale remain elusive, we used cholic acid (CA)-derived amphiphiles with different hydrophobicities as model antimicrobials and assessed the effect of their conformational flexibility on antimicrobial activity. Relative to other hydrophobic counterparts, a compound with a hexyl chain (6) showed the strongest binding with the lipopolysaccharide (LPS) of Gram-negative bacterial membranes and acted as an effective antimicrobial. Biomolecular simulations, validated by complementary approaches, revealed that specific intramolecular hydrogen bonding imparts conformationally rigid character to compound 6. This conformational stability of compound 6 allows minimum but specific interactions of the amphiphile with LPS that are a sum of exothermic processes like electrostatic interactions, membrane insertion, and endothermic contributions from disaggregation of LPS. Therefore, our study reveals that a membrane-targeting mechanism with the help of conformationally selective molecules offers a roadmap for developing future therapeutics against bacterial infections.

Alternatives to Conventional Antibiotics in the Era of Antimicrobial Resistance

As more antibiotics are rendered ineffective by drug-resistant bacteria, focus must be shifted towards alternative therapies for treating infections. Although several alternatives already exist in nature, the challenge is to implement them in clinical use. Advancements within biotechnology, genetic engineering, and synthetic chemistry have opened up new avenues towards the search for therapies that can substitute for antibiotics. This review provides an introduction to the various promising approaches that have been adopted in this regard. Whilst the use of bacteriophages and antibodies has been partly implemented, other promising strategies, such as probiotics, lysins, and antimicrobial peptides, are in various stages of development. Propitious concepts such as genetically modified phages, antibacterial oligonucleotides, and CRISPR-Cas9 are also discussed.

Matrix assisted antibacterial activity of polymer conjugates with pendant antibiotics, and bioactive and biopassive moieties

We report the comparative antibacterial activity of a polymer–antibiotic conjugate with coupled bioactive (cationic) and biopassive (zwitterionic) functionalities against several biofilm and nonbiofilm forming bacterial species in both liquid and solid matrices.

Aryl-Alkyl-Lysines Interact with Anionic Lipid Components of Bacterial Cell Envelope Eliciting Anti-Inflammatory and Antibiofilm Properties

The emergence of bacterial resistance and hesitance in approving new drugs has bolstered research on membrane-active agents such as antimicrobial peptides and their synthetic derivatives as therapeutic alternatives against bacterial infections. Herein, we document the action of aryl-alkyl-lysines on liposomes mimicking bacterial membranes using solid-state nuclear magnetic resonance spectroscopy. A significant perturbation of the lipid thickness and order parameter of the lipid membrane was observed upon treatment with this class of compounds. Encouraged by these results, the ability of the most active compound (NCK-10) to interact with aggregates of lipopolysaccharides (LPSs) was studied. In vitro experiments showed that NCK-10 was able to prevent the LPS-induced stimulation of proinflammatory cytokines such as tumor necrosis factor-α and interleukin-6. The compound could also disrupt the biofilms of Pseudomonas aeruginosa in vitro and bring down the bacterial burden by more than 99% in a mice model of burn infections caused by the biofilms of P. aeruginosa.

The Perturbation of Pulmonary Surfactant by Bacterial Lipopolysaccharide and Its Reversal by Polymyxin B: Function and Structure

After inhalation, lipopolysaccharide (LPS) molecules interfere with a pulmonary surfactant, a unique mixture of phospholipids (PLs) and specific proteins that decreases surface tension at the air⁻liquid interphase. We evaluated the behaviour of a clinically used modified porcine pulmonary surfactant (PSUR) in the presence of LPS in a dynamic system mimicking the respiratory cycle. Polymyxin B (PxB), a cyclic amphipathic antibiotic, is able to bind to LPS and to PSUR membranes. We investigated the effect of PxB on the surface properties of the PSUR/LPS system. Particular attention was paid to mechanisms underlying the structural changes in surface-reducing features. The function and structure of the porcine surfactant mixed with LPS and PxB were tested with a pulsating bubble surfactometer, optical microscopy, and small- and wide-angle X-ray scattering (SAXS/WAXS). Only 1% LPS (w/w to surfactant PLs) prevented the PSUR from reaching the necessary low surface tension during area compression. LPS bound to the lipid bilayer of PSUR and disturbed its lamellar structure by swelling. The structural changes were attributed to the surface charge unbalance of the lipid bilayers due to LPS insertion. PxB acts as an inhibitor of structural disarrangement induced by LPS and restores original lamellar packing, as detected by polarised light microscopy and SAXS.

An MD2-derived peptide promotes LPS aggregation, facilitates its internalization in THP-1 cells, and inhibits LPS-induced pro-inflammatory responses

MD2, a 160-residue accessory glycoprotein, is responsible for the recognition and binding of Gram-negative bacterial membrane component, lipopolysaccharide (LPS). Internalization of pathogen inside the mononuclear phagocytes has also been attributed to MD2 which leads to the clearance of pathogens from the host. However, not much is known about the segments in MD2 that are responsible for LPS interaction or internalization of pathogen inside the defense cells. A 16-residue stretch (MD54) from MD2 protein has been identified that possesses a short heptad repeat sequence and four cationic residues enabling it to participate in both hydrophobic and electrostatic interactions with LPS. An MD54 analog of the same size was also designed in which a leucine residue at a heptadic position was replaced with an alanine residue. MD54 but not its analog, MMD54 induced aggregation of LPS and aided in its internalization within THP-1 monocytes. Furthermore, MD54 inhibited LPS-induced nuclear translocation of NF-κB in PMA-treated THP-1 and TLR4/MD2/CD14-transfected HEK-293T cells and the production of pro-inflammatory cytokines. In addition, in in vivo experiments, MD54 showed marked protection and survival of mice against LPS-induced inflammation and death. Overall, we have identified a short peptide with heptad repeat sequence from MD2 that can cause aggregation of LPS and abet in its internalization within THP-1 cells, resulting in attenuation of LPS-induced pro-inflammatory responses in vitro and in vivo.

Recent Advances in Antibacterial and Antiendotoxic Peptides or Proteins from Marine Resources

Infectious diseases caused by Gram-negative bacteria and sepsis induced by lipopolysaccharide (LPS) pose a major threat to humans and animals and cause millions of deaths each year. Marine organisms are a valuable resource library of bioactive products with huge medicinal potential. Among them, antibacterial and antiendotoxic peptides or proteins, which are composed of metabolically tolerable residues, are present in many marine species, including marine vertebrates, invertebrates and microorganisms. A lot of studies have reported that these marine peptides and proteins or their derivatives exhibit potent antibacterial activity and antiendotoxic activity in vitro and in vivo. However, their categories, heterologous expression in microorganisms, physicochemical factors affecting peptide or protein interactions with bacterial LPS and LPS-neutralizing mechanism are not well known. In this review, we highlight the characteristics and anti-infective activity of bifunctional peptides or proteins from marine resources as well as the challenges and strategies for further study.

Characterization of bactericidal efficiency, cell selectivity, and mechanism of short interspecific hybrid peptides

Facing rising global antibiotics resistance, physical membrane-damaging antimicrobial peptides (AMPs) represent promising antimicrobial agents. Various strategies to design effective hybrid peptides offer many advantages in overcoming the adverse effects of natural AMPs. In this study, hybrid peptides from different species were investigated, and three hybrid antimicrobial peptides, LI, LN, and LC, were designed by combining the typical fragment of human cathelicidin-derived LL37 with either indolicidin, pig nematode cecropin P1 (CP-1) or rat neutrophil peptide-1 (NP-1). In an aqueous solution, all hybrid peptides had an unordered conformation. In simulated membrane conditions, the hybrid peptide LI displayed more β-turn and β-hairpin structures, whereas LN and LC folded into α-helix structures. The three interspecific hybrid peptides LI, LN, and LC exhibited different levels of antimicrobial activity against Gram-positive and Gram-negative bacteria. LI demonstrated the highest antimicrobial activity and cell selectivity. The results of the swimming motility indicated that LI repressed bacterial motility in a concentration-dependent method. Endotoxin binding assay demonstrated that hybrid peptide LI conserved the binding ability to LPS (polyanionic lipopolysaccharides) of its parental peptides. Fluorescence assays, flow cytometry, and SEM further revealed that hybrid peptide LI acted through different bacteriostatic mechanisms than LL37 and indolicidin and that LI killed bacterial cells via membrane damage. In summary, this study demonstrated that hybrid peptide LI produced by interspecific hybrid synthesis possessed strong cell selectivity and is a promising therapeutic candidate for drug-resistant bacteria infection.

Membrane-active macromolecules kill antibiotic-tolerant bacteria and potentiate antibiotics towards Gram-negative bacteria

Chronic bacterial biofilms place a massive burden on healthcare due to the presence of antibiotic-tolerant dormant bacteria. Some of the conventional antibiotics such as erythromycin, vancomycin, linezolid, rifampicin etc. are inherently ineffective against Gram-negative bacteria, particularly in their biofilms. Here, we report membrane-active macromolecules that kill slow dividing stationary-phase and antibiotic tolerant cells of Gram-negative bacteria. More importantly, these molecules potentiate antibiotics (erythromycin and rifampicin) to biofilms of Gram-negative bacteria. These molecules eliminate planktonic bacteria that are liberated after dispersion of biofilms (dispersed cells). The membrane-active mechanism of these molecules forms the key for potentiating the established antibiotics. Further, we demonstrate that the combination of macromolecules and antibiotics significantly reduces bacterial burden in mouse burn and surgical wound infection models caused by Acinetobacter baumannii and Carbapenemase producing Klebsiella pneumoniae (KPC) clinical isolate respectively. Colistin, a well-known antibiotic targeting the lipopolysaccharide (LPS) of Gram-negative bacteria fails to kill antibiotic tolerant cells and dispersed cells (from biofilms) and bacteria develop resistance to it. On the contrary, these macromolecules prevent or delay the development of bacterial resistance to known antibiotics. Our findings emphasize the potential of targeting the bacterial membrane in antibiotic potentiation for disruption of biofilms and suggest a promising strategy towards developing therapies for topical treatment of Gram-negative infections.

Global Dynamic Proteome Study of a Pellicle-forming Acinetobacter baumannii Strain

For several decades, many bacteria, among which A. baumannii, have shown their ability to colonize the upper surface of static liquids, forming a biofilm at the air-liquid interface named pellicle. Despite the ubiquity of these pellicles in both natural and artificial environments, few studies have investigated this biofilm type. The present data set provides the first description of the whole proteome of A. baumannii cells grown as pellicle, using a label-free mass spectrometry approach. Results are in accord with the general findings reporting that sessile bacteria are far more resistant to detrimental conditions than their planktonic counterparts, by the accumulation of stress proteins. The present investigation also confirmed previous studies suggesting a correlation between the pellicle forming ability and the bacterial virulence. Indeed, we showed the up-regulation of numerous virulence factors during the pellicle growth, e.g. phospholipases, adhesion factors, as well as those of the GacAS Two-Component System (TCS) and Type 6 Secretion System (T6SS). We also highlighted that Bam and Tam systems, both related to the OM insertion machinery, play a critical role during pellicle biogenesis. Moreover, sessile bacteria activate several pathways, e.g. iron, magnesium, phosphate pathways, which allows for increasing the panel of nutrient sources.

Cyclization and unsaturation rather than isomerisation of side chains govern the selective antibacterial activity of cationic-amphiphilic polymers

The influence of cyclization and unsaturation on the hydrophobic side chains of cationic-amphiphilic polymers towards antibacterial activity and mammalian cell toxicity is reported.

Isosteric substitution in cationic-amphiphilic polymers reveals an important role for hydrogen bonding in bacterial membrane interactions

The important role of hydrogen bonding in the interactions of cationic-amphiphilic polymers with bacterial membranes has been reported.

Biomimetic antibacterial polymers, the functional mimics of antimicrobial peptides (AMPs), targeting the bacterial cell membrane have been developed to combat the problem of antibiotic resistance. Amphiphilicity, a balance of cationic charge and hydrophobicity, in these polymers has been shown to be pivotal for their selective interactions with anionic lipid membranes of bacteria instead of zwitterionic mammalian (human erythrocyte) membranes. However, it is unclear if and to what extent hydrogen bonding in amphiphilic antibacterial polymers contributes to this membrane binding specificity. To address this, we employ isosteric substitution of ester with amide moieties that differ in their potency for hydrogen bonding in the side chains of N-alkyl maleimide based amphiphilic polymers. Our studies reveal that amide polymer (AC3P) is a potent antibacterial agent with high membrane-disrupting properties compared to its ester counterpart (EC3P). To understand these differences we performed bio-physical experiments and molecular dynamics (MD) simulations which showed strong interactions of AC3P including hydrogen bonding with lipid head groups of bacterial model lipid bilayers, that are absent in EC3P, make them selective for bacterial membranes. Mechanistic investigations of these polymers in bacteria revealed specific membrane disruptive activity leading to the delocalization of cell division related proteins. This unprecedented and unique concept provides an understanding of bacterial membrane interactions highlighting the role of hydrogen bonding. Thus, these findings will have significant implications in efficient design of potent membrane-active agents.