Edwardsiella tarda can cause fatal gastro-/extraintestinal diseases in fish and humans. Overuse of antibiotics has led to antibiotic resistance and contamination in the environment, which highlights the need to find new antimicrobial agents. In this study, the marine peptide-N6 was amidated at its C-terminus to generate N6NH2. The antibacterial activity of N6 and N6NH2 against E. tarda was evaluated in vitro and in vivo; their stability, toxicity and mode of action were also determined. Minimal inhibitory concentrations (MICs) of N6 and N6NH2 against E. tarda were 1.29–3.2 μM. Both N6 and N6NH2 killed bacteria by destroying the cell membrane of E. tarda and binding to lipopolysaccharide (LPS) and genomic DNA. In contrast with N6, N6NH2 improved the stability toward trypsin, reduced hemolysis (by 0.19% at a concentration of 256 μg/mL) and enhanced the ability to penetrate the bacterial outer and inner membrane. In the model of fish peritonitis caused by E. tarda, superior to norfloxacin, N6NH2 improved the survival rate of fish, reduced the bacterial load on the organs, alleviated the organ injury and regulated the immunity of the liver and kidney. These data suggest that the marine peptide N6NH2 may be a candidate for novel antimicrobial agents against E. tarda infections.

Viral infectious diseases pose a serious threat to animal husbandry, especially in the pig industry. With the rapid, continuous variation of viruses, a series of therapeutic measures, including vaccines, have quickly lost their efficacy, leading to great losses for animal husbandry. Therefore, it is urgent to find new drugs with more stable and effective antiviral activity. Recently, it has been reported that antimicrobial peptides (AMPs) have great potential for development and application in animal husbandry because of their significant antibacterial and antiviral activity, and the antiviral ability of AMPs has become a research hotspot. This article aims to review the research situation of AMPs used to combat viruses in swine production of animal husbandry, clarify the mechanism of action of AMPs on viruses and raise some questions, and explore the future potential of AMPs in animal husbandry.

Piglets, especially weaning piglets, show a lower level of immunity and higher morbidity and mortality, owing to their rapid growth, physiological immaturity, and gradual reduction of maternal antibodies, which seriously affects their growth and thus, value. It is important that piglets adapt to nutrient digestion and absorption and develop sound intestinal function and colonization with gut microbiota as soon as possible during their early life stage. Lactoferrin is a natural glycoprotein polypeptide that is part of the transferrin family. It is widely found in mucosal secretions such as saliva and tears, and most highly in milk and colostrum. As a multifunctional bioactive protein and a recommended food additive, lactoferrin is a potential alternative therapy to antibiotics and health promoting additive for piglet nutrition and development. It is expected that lactoferrin, as a natural food additive, could play an important role in maintaining pig health and development. This review examines the following known beneficial effects of lactoferrin: improves the digestion and capacity for absorption in the intestinal tract; promotes the absorption of iron and reduces the incidence of iron deficiency anemia; regulates intestinal function and helps to balance the microbial biota; and enhances the resistance to disease of the piglets via modulating and enhancing the immune system.

Aeromonas veronii is one of the main pathogens causing various diseases in humans and animals. It is currently difficult to eradicate drug-resistant A. veronii due to the biofilm formation by conventional antibiotic treatments. In this study, a marine peptide-N6NH₂ and its analogs were generated by introducing Orn or replacing with D-amino acids, Val and Pro; their enzymic stability and antibacterial/antibiofilm ability against multi-drug resistant (MDR) A. veronii ACCC61732 were detected in vitro and in vivo, respectively. The results showed that DN6NH₂ more rapidly killed A. veronii ACCC61732 and had higher stability in trypsin, simulated gastric/intestinal fluid, proteinase K, and mouse serum than the parent peptide-N6NH₂. DN6NH₂ and other analogs significantly improved the ability of N6NH₂ to penetrate the outer membrane of A. veronii ACCC61732. DN6NH₂, N6PNH₂ and V112N6NH₂ protected mice from catheter-associated biofilm infection with MDR A. veronii ACCC61732, superior to N6NH₂ and CIP. DN6NH₂ had more potent efficacy at a dose of 5 μmol/kg (100% survival) in a mouse peritonitis model than other analogs (50–66.67%) and CIP (83.33%), and it inhibited the bacterial translocation, downregulated pro-inflammatory cytokines, upregulated the anti-inflammatory cytokine, and ameliorated multiple-organ injuries (including the liver, spleen, lung, and kidney). These data suggest that the analogs of N6NH₂ may be a candidate for novel antimicrobial and antibiofilm agents against MDR A. veronii infections.

Although antimicrobial peptides (AMPs) have highly desirable intrinsic characteristics in their commercial product development as new antimicrobials, the limitations of AMPs from experimental to scale development include the low oral bioavailability, and high production costs due to inadequate in vitro/in vivo gene expression- and low scale. Plectasin has good bactericidal activity against Staphylococcus and Streptococcus, and the selective bactericidal activity greatly reduces the damage to the micro-ecosystem when applied in vivo. However, its expression level was relatively low (748.63 mg/L). In view of these situations, this study will optimize and modify the structure of Plectasin, hoping to obtain candidates with high expression, no/low toxicity, and maintain desirable antibacterial activity. Through sequence alignment, Plectasin was used as a template to introduce the degenerate bases, and the screening library was constructed. After three different levels of screening, the candidate sequence PN7 was obtained, and its total protein yield in the supernatant was 5.53 g/L, with the highest value so far for the variants or constructs from the same ancestor source. PN7 had strong activity against several species of Gram-positive bacteria (MIC value range 1~16 μg/mL). It was relatively stable in various conditions in vitro; in addition, the peptide showed no toxicity to mice for 1 week after intraperitoneal injection. Meanwhile, PN7 kills Staphylococcus aureus ATCC 43300 with a mode of a quicker (>99% S. aureus was killed within 2 h, whereas vancomycin at 2× MIC was 8 h.) and longer PAE period. The findings indicate that PN7 may be a novel promising antimicrobial agent, and this study also provides a model or an example for the design, modification, or reconstruction of novel AMPs and their derivatives.

The pervasive misuse of antibiotics has precipitated a global crisis of antimicrobial resistance (AMR), epitomized by the proliferation of methicillin-resistant Staphylococcus aureus (MRSA). Marine-derived antimicrobial peptides (AMPs) have emerged as promising alternatives, exhibiting broad therapeutic potential, including antimicrobial and anticancer activities. This review summarizes recent advances in marine AMPs, encompassing resource exploration, preparation methods, and biomedical applications, while addressing challenges such as instability and limited scalability. Future perspectives emphasize rational AMPs design to enhance efficacy and safety, alongside synergistic combination strategies, underscoring the potential of marine AMPs as viable interventions against drug-resistant pathogens.