Antibacterial and Antifungal Potential of Hermetia illucens Hemolymph Contained-Peptides.

Abstract

Antimicrobial peptides (AMPs) constitute a chemically and structurally heterogeneous family of molecules produced by a wide range of living organisms, including plants, fish, amphibians, mammals, and insects. Their expression is particularly high in hosts frequently exposed to microorganisms, where AMPs play a key role in innate immune responses. Insects represent one of the richest natural sources of AMPs. Over their long evolutionary history, they have developed a highly efficient immune system with AMPs playing a central role in defense against pathogens, enabling them to colonize various habitats. In recent years, interest in AMPs has significantly increased due to the emergence of antibiotic resistance, positioning these peptides as potential therapeutic alternatives for treating infections caused by multi-resistant pathogens. In this study, we investigated the antimicrobial activity of peptide fractions extracted from the hemolymph of Hermetia illucens larvae (Diptera, Stratiomyidae), an insect known for its high expression of AMPs. Larvae were injected separately with either Escherichia coli (Gram-negative) or Micrococcus flavus (Gram-positive), and hemolymph was collected 24 h post-infection, as well as from uninfected larvae. Antimicrobial activity was assessed through microbiological assays, including both agar diffusion tests and microdilution assays. Results demonstrated significant activity against pathogenic bacterial strains, including antibiotic-resistant ones. The Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) were determined for each experimental condition. MIC values ranged from 0.023 to 0.375 µg·µL⁻¹, while MBC values ranged from 0.187 to 0.750 µg·µL⁻¹, depending on the bacterial strain and the infection treatment group. These findings demonstrate the potential of H. illucens-derived AMPs as effective agents against Gram-positive and Gram-negative bacteria, including resistant strains, and support their further development as alternatives or adjuvants to conventional antibiotics.