2.10 Antimicrobial peptides
AMPs, also known as host defense peptides, are short, positively charged proteins found in many organisms, including humans. They have the ability to directly eliminate harmful microbes or enhance the body’s immune response. With the growing issue of antibiotic resistance, AMPs are being recognized as potential therapeutic solutions. They provide quick and targeted action against bacteria that are resistant to traditional antibiotics and have a low risk of developing resistance, positioning them as excellent options for antibacterial treatments.25 Bacteria often produce AMPs to fight off rival bacteria within their environment.26Gram-positive and Gram-negative bacteria have membranes with negatively charged lipids that attract the positively charged AMPs. In Gram-negative bacteria, AMPs first need to breach the outer membrane, which is strengthened by cations like calcium and magnesium attached to lipopolysaccharides. AMPs likely use a method where they displace these cations, creating temporary openings in the outer membrane for entry.25,27 Antimicrobial peptides (AMPs) fight bacteria mainly by interacting with their membranes in different ways. Some peptides insert into the membrane to create pores, while others coat the membrane surface and disrupt it like a detergent when they reach a high concentration. Additionally, some peptides cause the membrane to bend around a central opening. AMPs can also block the creation of cell walls and inhibit the production of proteins or genetic material. Among the most studied AMPs are insect-derived peptides, particularly cecropins, which effectively target bacteria like E. coli by damaging their membranes.28 AMPs causes ion leakage and depolarization that lead to membrane dysfunction and rapid cell lysis.29 Although bacteria are less likely to resist AMPs due to their multiple targets, recent studies show that resistance can develop under selective pressure, and AMPs also face challenges due to low stability and high production costs.25,30 In ovo treatment with D-CATH-2 reduced APEC mortality and bacterial load in chickens. Combining surfactin with amoxicillin enhanced its effectiveness, lowering mortality and APEC levels while boosting cytokine genes. Peptides like A3 and cecropin A-D-Asn also decreasedE. coli in the chicken gut, suggesting antimicrobial peptides as alternatives or supplements to antibiotics in poultry.2,31