Combating Escherichia coli O157:H7 with Functionalized Chickpea-Derived Antimicrobial Peptides

The discovery of novel antimicrobial peptides against drug-resistant bacteria based on fragments fusion strategy

Since the escalating prevalence of multidrug-resistant (MDR) bacterial infections posing global health challenges, novel antimicrobial agents are urgently needed. This study designed a series of antimicrobial peptides by fusing two fragments of antimicrobial peptides sC184b (1-9) and MSI-78 (10-16). Among these peptides, 13DKallDab exhibited broad-spectrum antimicrobial efficacy against six different MDR bacterial strains with relatively low MICs. It exerted antibacterial effects through a membrane-disruption mechanism and maintained high stability in serum environment. Moreover, 13DKallDab displayed low cytotoxicity and hemolysis in vitro, and significant therapeutic efficacy in a mouse acute peritonitis model. These findings demonstrate that 13DKallDab is a promising antimicrobial agent in counteracting multidrug-resistant bacterial infections.

Combined impact of biosynthesized selenium nanoparticles and imipenem against carbapenem-resistant Pseudomonas aeruginosa and their associated virulence factors

BACKGROUND

Carbapenem-resistant P. aeruginosa (CRPA) is a significant nosocomial pathogen characterized by extensive antibiotic resistance, representing a serious public health concern. It is regarded as a high-priority target for antibacterial research. This study aimed to isolate and identify CRPA isolates and the biosynthesis of selenium nanoparticles (Se-NPs) as a novel therapeutic approach for combating CRPA strains and their capacity to form biofilms, alone or in combination with imipenem.

METHODS

CRPA isolates were isolated from different clinical samples, identified, and subjected to antibiotic profiling using Vitek-2 method. The detection of biofilm was performed using Congo red agar (CRA), Microdilution broth assay (MBA), and qRT-PCR detection of Bap and ompA genes. Biosynthesis of Se-NPs with a cell-free filter (CFF) of Streptomyces sp. was done and characterized with various techniques, including UV-Vis, XRD, TEM, FTIR, and Zeta potential measurement. The antibacterial efficacy and minimum inhibitory concentrations (MICs) were determined using disc diffusion and microdilution techniques. The checkerboard assay was used to formulate various combinations of imipenem and Se-NPs, alongside time-kill assays to assess their antimicrobial efficacy. Furthermore, the cytotoxic effects and hemolytic activity of Se-NPs, imipenem and their combination were assessed.

RESULTS

The identification process and antibiotic susceptibility testing confirmed that the bacterial isolates were found to be CRPA. Phenotypic analysis revealed that the CRPA produced biofilm, and qRT-PCR demonstrated that all CRPA strains under study have the Bap and ompA genes. The CFF of Streptomyces sp. was able to biosynthesize Se-NPs which presented UV-Visible spectrometric profile with sharp peak at 290 nm. Se-NPs appeared to be a spherical shape, with particle sizes ranging from 20 to 100 nm under TEM and have zeta potential value of -40 mV. The MICs of Se-NPs and imipenem ranged from 6 to 14 and 12 to 14 µg/ml, respectively. The fractional inhibitory concentration index (FICI) values ranged from 0.37 to 0.50 against tested CRPA strain with a significant reduction in the concentrations of Se-NPs and imipenem. QRT-PCR showed that Se-NPs alone or combination of Se-NPs and imipenem led to a reduction of Bap and ompA gene expression compared to control (p ≤ 0.0001). The study showed a significant difference in cell viability was observed across normal or cancer cell lines at high concentrations. However, the combination of Se-NPs and imipenem demonstrated enhanced selectivity toward cancer cells, with HepG-2 cells showing significantly lower viability compared to normal HFP-4 cells across all tested concentrations. Se-NPs alone showed moderate hemolysis percentages of 1.9% at 12 h and 2.3% at 24 h while the hemolytic activity Se-NPs and imipenem combination was reduced to 1.4% and 1.7% at 12 and 24 h, representing approximately 26% and 26% reductions in haemolysis compared to Se-NPs alone at the respective time points.

CONCLUSION

This study confirms that the biosynthesized Se-NPs exhibit potent synergistic effects with imipenem against CRPA, significantly reducing biofilm formation and the expression of virulence genes Bap and ompA.

The α-Helical Antibacterial Peptides Derived from Mastoparan with Broad-Spectrum Activity against Multidrug-Resistant Pathogens

The overuse and misuse of antibiotics resulted in the emergence of multidrug-resistant bacteria. As a promising solution, antimicrobial peptides have attracted much attention. In this research, a series of peptides derived from MP9 through the substitution of tryptophan for alanine and the rearrangement of amino acid residues were designed and synthesized. MP9-10 displayed the highest anti-multidrug-resistant bacterial activity and the lowest cytotoxicity as well as hemolysis among all the derivates. Membrane disruption was the main mechanism for MP9-10 to kill bacteria. The in vivo results on mice also demonstrated that MP9-10 had the capacity to treat infections caused by Staphylococcus aureus bacteria. In summary, MP9-10 is a promising candidate for the treatment of multidrug-resistant bacterial infections.

Development of targeted antimicrobial peptides for Escherichia coli: Combining phage display and rational design for food safety application

The growing demand for minimally processed foods has heightened the risk of pathogenic contamination. Balancing antimicrobial efficacy with the preservation of probiotic activity remains a significant challenge. In this study, we employed phage display peptide library screening, combined with next-generation sequencing to identify the HIMPIQA domain, which selectively targets pathogenic Escherichia coli (E. coli) in just one screening round. Using the yXy(PX)4yXy template, we designed antimicrobial peptides (AMPs) where 'y' represents hydrophobic amino acids, and 'X' represents positively charged residues. The peptide WK, combining HIMPIQA with a Trp/Lys-based antimicrobial domain, demonstrated high specificity and antibacterial activity. Molecular docking revealed WK's binding to FaeG and mechanistic studies showed its ability to disrupt E. coli membranes while maintaining probiotic viability. WK's application as a preservative enhanced the shelf life of yogurt and tomatoes. This innovative approach showcases the potential of phage display in developing targeted AMPs for food preservation and safety.

Imaging-based profiling for elucidation of antibacterial mechanisms of action

In this review, we aim to summarize experimental data and approaches to identifying cellular targets or mechanisms of action of antibacterials based on imaging techniques. Imaging-based profiling methods, such as bacterial cytological profiling, dynamic bacterial morphology imaging, and others, have become a useful research tool for mechanistic studies of new antibiotics as well as combinations with conventional ones and other therapeutic options. The main methodological and experimental details and obtained results are summarized and discussed. The review covers the literature up to February 2024.

Isolation and characterization of quinoa antimicrobial peptides and its effect on the microbial diversity of fresh apple juice

This study developed antimicrobial peptides (AMPs) from quinoa with high antibacterial activity and stability by mixed-bacteria fermentation. Furthermore, among 9 peptide fractions purified by membrane separation and chromatography, F1 could effectively inhibit the growth and propagation of bacterial microorganisms in apple juice. Subsequently, F1 identified LC-MS/MS as 95 peptides, molecular weights 494.25 Da to 1253.55 Da, notably, AGAAPE peptide (556.25 Da), negatively charged (-1), highly hydrophobic (50 %), with significant inhibitory effects on both Escherichia coli and Staphylococcus aureus (MIC 5 mg/mL). The antimicrobial mechanism of AGAAPE was determined to damage membrane through hydrogen-bond and hydrophobic interactions, resulting in leakage of intramembrane substances and inhibition of intracellular ATPase activity. Moreover, AGAAPE was pH resistant (pH 4-12), thermally stable (121 °C, 30 min), resistant to salt ion interference (Na+, Ca2+), and protease hydrolysis resistant (neutral protease, pepsin, trypsin). Overall, identifying AMPs from quinoa provides a promising new approach for fresh juice preservation.

Advances and mechanisms of traditional Chinese medicine and its active ingredients against antibiotic-resistant Escherichia coli infections

In clinical practice, antibiotics have historically been utilized for the treatment of pathogenic bacteria. However, the gradual emergence of antibiotic resistance among bacterial strains has posed a significant challenge to this approach. In 2022, Escherichia coli, a Gram-negative bacterium renowned for its widespread pathogenicity and high virulence, emerged as the predominant pathogenic bacterium in China. The rapid emergence of antibiotic-resistant E. coli strains has rendered antibiotics insufficient to fight E. coli infections. Traditional Chinese medicine (TCM) has made remarkable contributions to the health of Chinese people for thousands of years, and its significant therapeutic effects have been proven in clinical practice. In this paper, we provide a comprehensive review of the advances and mechanisms of TCM and its active ingredients against antibiotic-resistant E. coli infections. First of all, this review introduces the classification, antibiotic resistance characteristics and mechanisms of E. coli. Then, the TCM formulas and extracts are listed along with their active ingredients against E. coli, including extraction solution, minimum inhibitory concentration (MIC), and the antibacterial mechanisms. In addition, there is growing evidence supporting the synergistic therapeutic strategy of combining TCM with antibiotics for the treatment of antibiotic-resistant E. coli infections, and we provide a summary of this evidence and its underlying mechanisms. In conclusion, we present a comprehensive review of TCM and highlight its potential and advantages in the prevention and treatment of E. coli infections. We hold the opinion that TCM will play an important role in global health, pharmaceutical development, and livestock farming in the future.

Antibacterial activity and multi-target mechanism of harmane against Escherichia coli O157:H7 and its application on ready-to-eat leafy greens

Escherichia coli O157:H7 has caused many foodborne disease outbreaks and resulted in unimaginable economic losses. With the evolution of food consumption, people prefer natural preservatives. In this study, the natural agent harmane exhibited potential activity against E. coli O157:H7 (MIC = 64 μg/mL). It exhibited bacteriostatic mode at 1 X and 2 X MIC treatment, and bactericidal mode at 4 X MIC treatment. Moreover, it showed good in vitro stability in sheep plasma, low in vitro hemolysis and no in vivo acute toxicity with LD50 > 50 mg/kg. Moreover, harmane significantly decreased the colony number of E. coli O157:H7 in fresh-cut lettuce samples after 5 days of storage without affecting appearance. The mechanism study elucidated that harmane significantly decomposed the mature biofilm by reducing exopolysaccharide contents, and killed the viable bacterial cells in biofilm. The cell wall was damaged by harmane via interacting with peptidoglycan. Fluorescent staining and intracellular macromolecular leakage assays showed that irreversible destruction to membrane permeability and integrity. When entering the cell, harmane could defeat the redox balance, suppress metabolic activity and target to ribosome. These findings not only revealed the application potential of harmane as new natural preservative, but also preliminarily elucidated the multi-target mechanism, providing a new strategy for controlling E. coli O157:H7 in the food industry.

Antimicrobial peptide Hs02 with rapid bactericidal, anti-biofilm, and anti-inflammatory activity against carbapenem-resistant Klebsiella pneumoniae and Escherichia coli

Carbapenem-resistant Klebsiella pneumoniae (CRKP) and Escherichia coli (CREC) are frequently detected in clinical settings, restricting the use of carbapenems. Therefore, there is an urgent need for new antimicrobial strategies to address infections caused by CRKP and CREC. This study investigated the antibacterial, anti-biofilm, and anti-inflammatory effects of the cationic antimicrobial peptide Hs02, along with its potential antimicrobial mechanisms against CRKP and CREC. The results revealed that Hs02 had a low minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against CRKP and CREC, effectively eliminating the bacteria within 30 min. Moreover, Hs02 significantly prevents biofilm formation and disrupts the established biofilms. Further mechanistic studies demonstrated that Hs02 specifically targeted and bound to bacterial outer membrane lipopolysaccharides (LPS), disrupted membrane permeability and integrity, which led to intracellular reactive oxygen species (ROS) accumulation. Furthermore, Hs02 neutralized LPS, thereby suppressing the production of pro-inflammatory cytokines TNF-α, IL-6, and IL-1β in murine macrophage RAW 264.7 cells. In vitro, hemolysis and cytotoxicity assays confirmed Hs02's safety at the tested concentrations and proved that Hs02 improved the survival rate of Galleria mellonella larvae. In conclusion, the findings suggest that Hs02's interaction with LPS and the resulting disruption of membrane integrity may be key factors driving its rapid bactericidal and anti-inflammatory effects.

IMPORTANCE

Eukaryotic antimicrobial peptides are typically amphipathic peptides consisting of approximately 50 amino acids. Many macromolecular proteins in our body contain polypeptide sequences that show characteristics similar to those of antimicrobial peptides. The present research highlights a gap in the current literature regarding the mechanisms by which the intragenic antimicrobial peptide Hs02, derived from human proteins, exerts its rapid bactericidal and anti-inflammatory effects. The findings demonstrate that lipopolysaccharide (LPS) is a key target of Hs02's antimicrobial activity and that its ability to neutralize LPS is crucial for its anti-inflammatory effects.

Functional antimicrobial peptide-loaded 3D scaffolds for infected bone defect treatment with AI and multidimensional printing

Infection is the most prevalent complication of fractures, particularly in open fractures, and often leads to severe consequences. The emergence of bacterial resistance has significantly exacerbated the burden of infection in clinical practice, making infection control a significant treatment challenge for infectious bone defects. The implantation of a structural stent is necessary to treat large bone defects despite the increased risk of infection. Therefore, there is a need for the development of novel antibacterial therapies. The advancement in antibacterial biomaterials and new antimicrobial drugs offers fresh perspectives on antibacterial treatment. Although antimicrobial 3D scaffolds are currently under intense research focus, relying solely on material properties or antibiotic action remains insufficient. Antimicrobial peptides (AMPs) are one of the most promising new antibacterial therapy approaches. This review discusses the underlying mechanisms behind infectious bone defects and presents research findings on antimicrobial peptides, specifically emphasizing their mechanisms and optimization strategies. We also explore the potential prospects of utilizing antimicrobial peptides in treating infectious bone defects. Furthermore, we propose that artificial intelligence (AI) algorithms can be utilized for predicting the pharmacokinetic properties of AMPs, including absorption, distribution, metabolism, and excretion, and by combining information from genomics, proteomics, metabolomics, and clinical studies with computational models driven by machine learning algorithms, scientists can gain a comprehensive understanding of AMPs' mechanisms of action, therapeutic potential, and optimizing treatment strategies tailored to individual patients, and through interdisciplinary collaborations between computer scientists, biologists, and clinicians, the full potential of AI in accelerating the discovery and development of novel AMPs will be realized. Besides, with the continuous advancements in 3D/4D/5D/6D technology and its integration into bone scaffold materials, we anticipate remarkable progress in the field of regenerative medicine. This review summarizes relevant research on the optimal future for the treatment of infectious bone defects, provides guidance for future novel treatment strategies combining multi-dimensional printing with new antimicrobial agents, and provides a novel and effective solution to the current challenges in the field of bone regeneration.

Targeting the outer membrane of gram-negative foodborne pathogens for food safety: compositions, functions, and disruption strategies

Foodborne pathogens are a major threat to both food safety and public health. The current trend toward fresh and less processed foods and the misuse of antibiotics in food production have made controlling these pathogens even more challenging. The outer membrane has been employed as a practical target to combat foodborne Gram-negative pathogens due to its accessibility and importance. In this review, the compositions of the outer membrane are extensively described firstly, to offer a thorough overview of this target. Current strategies for disrupting the outer membrane are also discussed, with emphasized on their mechanism of action. The disruption of the outer membrane structure, whether caused by severe damage of the lipid bilayer or by interference with the biosynthesis pathway, has been demonstrated to represent an effective antimicrobial strategy. Interference with the outer membrane-mediated functions of barrier, efflux and adhesion also contributes to the fight against Gram-negative pathogens. Their potential for control of foodborne pathogens in the production chain are also proposed. However, it is possible that multiple components in the food matrix may act as a protective barrier against microorganisms, and it is often the case that contamination is not caused by a single microorganism. Further investigation is needed to determine the effectiveness and safety of these methods in more complex systems, and it may be advisable to consider a multi-technology combined approach. Additionally, further studies on outer membranes are necessary to discover more promising mechanisms of action.

Membrane Disruption-Enhanced Photodynamic Therapy against Gram-Negative Bacteria by a Peptide-Photosensitizer Conjugate

Photodynamic therapy (PDT) emerges as a promising strategy for combating bacteria with minimal drug resistance. However, a significant hurdle lies in the ineffectiveness of most photosensitizers against Gram-negative bacteria, primarily attributable to their characteristic impermeable outer membrane (OM) barrier. To tackle this obstacle, we herein report an amphipathic peptide-photosensitizer conjugate (PPC) with intrinsic outer membrane disruption capability to enhance PDT efficiency against Gram-negative bacteria. PPC is constructed by conjugating a hydrophilic ultrashort cationic peptide to a hydrophobic photosensitizer. PPC could efficiently bind to the OM of Gram-negative bacteria through electrostatic adsorption, and subsequently disrupt the structural integrity of the OM. Mechanistic investigations revealed that PPC triggers membrane disruption by binding to both lipopolysaccharide (LPS) and phospholipid leaflet in the OM, enabling effective penetration of PPC into the Gram-negative bacteria interior. Upon light irradiation, PPC inside bacteria generates singlet oxygen not only to effectively decrease the survival of Gram-negative bacteria P. aeruginosa and E. coli to nearly zero in vitro, but also successfully cure the full-thickness skin infection and bacterial keratitis (BK) induced by P. aeruginosa in animal models. Thus, this study provides a broad-spectrum antibacterial phototherapeutic design strategy by the synergistic action of membrane disruption and PDT to combat Gram-negative bacteria.

Chickpea-Derived Modified Antimicrobial Peptides KTA and KTR Inactivate Staphylococcus aureus via Disrupting Cell Membrane and Interfering with Peptidoglycan Synthesis

The widespread bacterial contamination caused by foodborne pathogens has continuously driven the development of advanced and potent food antimicrobial agents. In this study, two novel antimicrobial peptides (AMPs) named KTA and KTR were obtained by modifying a natural AMP, Leg2, from chickpea storage protein legumin hydrolysates. They were further predicted to be stable hydrophobic cationic AMPs of α-helical structure with no hemolytic toxicity by several online servers. Moreover, the AMPs exerted superior antibacterial activity against two representative Staphylococcus aureus strains thanks to the increased hydrophobicity and positive charge, with minimum inhibition concentration value (4.74-7.41 μM) significantly lower than that of Leg2 (>1158.70 μM). Further, this study sought to elucidate the specific antimicrobial mechanism against Gram-positive bacteria. It was found that the electrostatic interactions of the AMPs with peptidoglycan were vital for peptide activity in combating Gram-positive bacteria. Subsequently, the cell membrane of S. aureus cells was irreversibly disrupted by increasing permeability and impairing membrane components, which led to the massive release of intracellular substances and eventual cell death. Overall, this work demonstrated that KTA and KTR were active against Gram-positive bacteria via peptidoglycan targeting and membrane-disruptive mechanisms and paved the way for expanding their application potential to alleviate food contamination.

Antibacterial efficiency of the curcumin-mediated photodynamic inactivation coupled with L-arginine against Vibrio parahaemolyticus and its application on shrimp

The aim of this study was to investigate the antibacterial potency of a novel photodynamic inactivation (PDI) system with an enhanced bactericidal ability against Vibrio parahaemolyticus in vitro and in vivo. The synergistically bactericidal action of curcumin (Cur) and L-arginine (L-Arg) was firstly investigated, and then a novel curcumin-mediated PDI coupled with L-Arg was developed. Meanwhile, its potent inactivation mechanism against V. parahaemolyticus and preservation effects on shrimp were explored. Results showed that L-Arg disrupted the cell membrane by binding to membrane phospholipids and disrupting iron homeostasis, which helped curcumin to damage DNA and interrupt protein synthesis. Once irradiated by blue LED, the curcumin-mediated PDI produced the reactive oxygen species (ROS) which reacted with L-Arg to generate NO, and the NO was converted to reactive nitrogen species (RNS) with a strong bactericidal ability by consuming ROS. On this basis, the curcumin-mediated PDI coupled with L-Arg potently killed >8.0 Log CFU/mL with 8 μM curcumin, 0.5 mg/mL L-Arg and 1.2 J/cm2 irradiation. Meanwhile, this PDI also effectively inhibited the colour and pH changes, lipids oxidation and protein degradation of shrimp. Therefore, this study proposes a new potent PDI system to control microbial contamination in the food industry.

Ultrasonically functionalized chitosan-gallic acid films inactivate Staphylococcus aureus through envelope-disruption under UVA light exposure

The significant threat of foodborne pathogens contamination has continuously promoted the development of efficient antimicrobial food packaging materials. Here, an antimicrobial film was prepared with gallic acid-grafted-chitosan (CS/GA) that obtained by a two-step ultrasound method. The resultant films exhibited good transparency, improved UV barrier performance, and enhanced mechanical strength. Specifically, with the grafting of 1.2 % GA, the UV blocking ability of CS/GA film at 400 nm was significantly increased by 19.7 % and the tensile strength was nearly two times higher than that of CS film. Moreover, the CS/GA films exhibited an inspiring photoactivated bactericidal ability under 400 nm UVA light irradiation that eradicated almost 99.9 % of Staphylococcus aureus (S. aureus) cells within 60 min. To gain more insights into the antibacterial mechanism, the treated S. aureus cells were further investigated by visualizing bacterial ultrastructure and analyzing membrane properties. The results pointed to the peptidoglycan layer as the primary action target when bacteria come into contact with CS/GA films. Afterward, the intracellular oxidative lesions, disrupted bacterial integrity, and disordered membrane functional properties collectively resulted in eventual cell death. The findings revealed the unique peptidoglycan targeting and membrane disruptive mechanisms of CS/GA films, confirming the application values in controlling foodborne pathogens.

Super Antibacterial Capacity and Cell Envelope-Disruptive Mechanism of Ultrasonically Grafted N-Halamine PBAT/PBF Films against Escherichia coli

Antibacterial materials are urgently needed to combat bacterial contamination, growth, or attachment on contact surfaces, as bacterial infections remain a public health crisis worldwide. Here, a novel ultrasound-assisted method is utilized for the first time to fabricate oxidative chlorine-loaded AH@PBAT/PBF-Cl films with more superior grafting efficiency and rechargeable antibacterial effect than those from conventional techniques. The films remarkably inactivate 99.9999% Escherichia coli and Staphylococcus aureus cells, inducing noticeable cell deformations and mechanical instability. The specific antibacterial mechanism against E. coli used as a model organism is unveiled using several cell envelope structural and functional analyses combined with proteomics, peptidoglycomics, and fluorescence probe techniques. Film treatment partially neutralizes the bacterial surface charge, induces oxidative stress and cytoskeleton deformity, alters membrane properties, and disrupts the expression of key proteins involved in the synthesis and transport of the lipopolysaccharide and peptidoglycan, indicating the cell envelope as the primary target. The films specifically target lipopolysaccharides, resulting in structural impairment of the polysaccharide and lipid A components, and inhibit peptidoglycan precursor synthesis. Together, these lead to metabolic disorders, membrane dysfunction, structural collapse, and eventual death. Given the films' antibacterial effects via the disruption of key cell envelope components, they can potentially combat a wide range of bacteria. These findings lay a theoretical basis for developing efficient antibacterial materials for food safety or biomedical applications.