Phage-displayed heptapeptide sequence conjugation significantly improves the specific targeting ability of antimicrobial peptides against Staphylococcus aureus.

Broad-spectrum antibacterial drugs often lack specificity, leading to indiscriminate bactericidal activity, which can disrupt the normal microbial balance of the host flora and cause unnecessary cytotoxicity during systemic administration. In this study, we constructed a specifically targeted antimicrobial peptide against Staphylococcus aureus by introducing a phage-displayed peptide onto a broad-spectrum antimicrobial peptide and explored its structure-function relationship through one-factor modification. SFK2 obtained by screening based on the selectivity index and the targeting index showed specific killing ability against S. aureus. Moreover, SFK2 showed excellent biocompatibility in mice and piglet, and demonstrated significant therapeutic efficacy against S. aureus infection. In conclusion, our screening of phage-derived heptapeptides effectively enhances the specific bactericidal ability of the antimicrobial peptides against S. aureus, providing a theoretical basis for developing targeted antimicrobial peptides.

Staphylococcus aureus and biofilms: transmission, threats, and promising strategies in animal husbandry.

Staphylococcus aureus (S. aureus) is a common pathogenic bacterium in animal husbandry that can cause diseases such as mastitis, skin infections, arthritis, and other ailments. The formation of biofilms threatens and exacerbates S. aureus infection by allowing the bacteria to adhere to pathological areas and livestock product surfaces, thus triggering animal health crises and safety issues with livestock products. To solve this problem, in this review, we provide a brief overview of the harm caused by S. aureus and its biofilms on livestock and animal byproducts (meat and dairy products). We also describe the ways in which S. aureus spreads in animals and the threats it poses to the livestock industry. The processes and molecular mechanisms involved in biofilm formation are then explained. Finally, we discuss strategies for the removal and eradication of S. aureus and biofilms in animal husbandry, including the use of antimicrobial peptides, plant extracts, nanoparticles, phages, and antibodies. These strategies to reduce the spread of S. aureus in animal husbandry help maintain livestock health and improve productivity to ensure the ecologically sustainable development of animal husbandry and the safety of livestock products.

Design of High-Selectivity Co-Assembled Peptide Nanofibers against Bacterial Infection in Piglets.

Antibiotic resistance is an escalating global health concern that could result in tens of millions of deaths annually from drug-resistant bacterial infections in the future, especially in animal husbandry. Peptide antibacterial nanomaterials offer a competitive alternative to antibiotics because of their distinct mechanism of physically penetrating pathogenic biological membranes. This study developed amphiphilic co-assembled peptide nanofibers with high biological selectivity (PCBP-NCAP NFs) to overcome the high cytotoxicity of peptide PCBP and the low antibacterial activity of peptide NCAP. PCBP-NCAP NFs exhibit broad-spectrum antibacterial activity and excellent biocompatibility, with negligible in vivo and in vitro toxicity. Additionally, PCBP-NCAP NFs possess direct antibacterial efficacy and potential immunomodulatory capabilities using a piglet systemic infection model. Its unique mechanism of membrane penetration and the ability to bind to anionic components on the surface of pathogenic bacteria make them less susceptible to drug resistance. In conclusion, these findings have significant implications for the advancement of supramolecular peptide nanomedicines for clinical application and animal husbandry.

pH-Triggered Size-Transformable and Bioactivity-Switchable Self-Assembling Chimeric Peptide Nanoassemblies for Combating Drug-Resistant Bacteria and Biofilms.

Drug-resistant bacteria and biofilm-associated infections are prominent problems in the field of antibacterial medicine, seriously affecting human and animal health. Despite the great potential of nanomaterials in the antibacterial field, overcoming the paradox of size and charge, efficient penetration, and retention within biofilms remain a formidable challenge. Here, self-assembling chimeric peptide nanoassemblies composed of multiple functional fragments are designed for the treatment of drug-resistant bacteria and biofilm-associated infections. Notably, the chimeric peptide self-assembles into nanofibers at pH 7.4 and is transformable into nanoparticles in the acidic biofilm-infected microenvironment at pH 5.0, and thus achieves a size reduction and charge increase, improving the penetration into the bacterial biofilms and killing drug-resistant bacteria by a mechanism dominated by membrane cleavage. In vivo mouse and piglet infection models confirm the ability of chimeric peptide nanoassemblies to reduce bacterial load within biofilms. Collectively, this research on pathological-environment-driven nanostructural transformations may provide a theoretical basis for designing high-performance antibacterial nanomaterials and advance the application of peptide-based nanomaterials in medicine and animal husbandry.

Hydrophobic modification improves the delivery of cell-penetrating peptides to eliminate intracellular pathogens in animals.

Infections induced by intracellular pathogens are difficult to eradicate due to poor penetration of antimicrobials into cell membranes. It is of great importance to develop a new generation of antibacterial agents with dual functions of efficient cell penetration and bacterial inhibition. In this study, the association between hydrophobicity and cell-penetrating peptide delivery efficiency was investigated by fragment interception and hydrophobicity modification of natural porcine antimicrobial peptide PR-39 and the combination of cationic cell-penetrating peptide (R6) with antimicrobial peptide fragments modified with hydrophobic residues. The chimeric peptides P3I7 and P3L7, obtained through biofunctional screening, exhibited potent broad-spectrum antibacterial activity and low cytotoxicity. Moreover, P3I7 and P3L7 can effectively penetrate cells to eliminate intracellular pathogens mainly through endocytosis. The membrane destruction mechanism makes the peptides fast sterilizers and less prone to developing drug resistance. Finally, their good biocompatibility and antibacterial infection effects were verified in mice and piglets. To conclude, the chimeric peptides P3I7 and P3L7 show great potential as affordable and effective antimicrobial agents and may serve as ideal candidates for the treatment of intracellular bacterial infections. STATEMENT OF SIGNIFICANCE: The low permeability of antibacterial drugs makes infections induced by intracellular bacteria extremely difficult to treat. To address this issue, we designed chimeric peptides with dual cell-penetrating and antibacterial functions. The active peptides P3I7 and P3L7, acquired through functional screening have strong broad-spectrum antibacterial activity and powerful bactericidal effects against intracellular Staphylococcus aureus. The membrane permeation mechanism of P3I7 and P3L7 against bacteria endows fast bactericidal activity with low drug resistance. The biosafety and antibacterial activity of P3I7 and P3L7 were also validated by in vivo trials. This study provides an ideal drug candidate against intracellular bacterial infections.

Designing Self-Assembling Chimeric Peptide Nanoparticles with High Stability for Combating Piglet Bacterial Infections.

As a novel type of antibiotic alternative, peptide-based antibacterial drug shows potential application prospects attributable to their unique mechanism for lysing the membrane of pathogenic bacteria. However, peptide-based antibacterial drugs suffer from a series of problems, most notably their immature stability, which seriously hinders their application. In this study, self-assembling chimeric peptide nanoparticles (which offer excellent stability in the presence of proteases and salts) are constructed and applied to the treatment of bacterial infections. In vitro studies are used to demonstrate that peptide nanoparticles NPs1 and NPs2 offer broad-spectrum antibacterial activity and desirable biocompatibility, and they retain their antibacterial ability in physiological salt environments. Peptide nanoparticles NPs1 and NPs2 can resist degradation under high concentrations of proteases. In vivo studies illustrate that the toxicity caused by peptide nanoparticles NPs1 and NPs2 is negligible, and these nanoparticles can alleviate systemic bacterial infections in mice and piglets. The membrane permeation mechanism and interference with the cell cycle differ from that of antibiotics and mean that the nanoparticles are at a lower risk of inducing drug resistance. Collectively, these advances may accelerate the development of peptide-based antibacterial nanomaterials and can be applied to the construction of supramolecular nanomaterials.