Antimicrobial Peptides from Rat-Tailed Maggots of the Drone Fly Eristalis tenax Show Potent Activity against Multidrug-Resistant Gram-Negative Bacteria

Abstract

The spread of multidrug-resistant Gram-negative bacteria is an increasing threat to human health, because novel compound classes for the development of antibiotics have not been discovered for decades. Antimicrobial peptides (AMPs) may provide a much-needed breakthrough because these immunity-related defense molecules protect many eukaryotes against Gram-negative pathogens. Recent concepts in evolutionary immunology predict the presence of potent AMPs in insects that have adapted to survive in habitats with extreme microbial contamination. For example, the saprophagous and coprophagous maggots of the drone fly Eristalis tenax (Diptera) can flourish in polluted aquatic habitats, such as sewage tanks and farmyard liquid manure storage pits. We used next-generation sequencing to screen the E. tenax immunity-related transcriptome for AMPs that are synthesized in response to the injection of bacterial lipopolysaccharide. We identified 22 AMPs and selected nine for larger-scale synthesis to test their activity against a broad spectrum of pathogens, including multidrug-resistant Gram-negative bacteria. Two cecropin-like peptides (EtCec1-a and EtCec2-a) and a diptericin-like peptide (EtDip) displayed strong activity against the pathogens, even under simulated physiological conditions, and also achieved a good therapeutic window. Therefore, these AMPs could be used as leads for the development of novel antibiotics.

Identification of Antimicrobial Property of Rat-Tailed Maggots Surviving in Pig Excreta

“…We found that, rat-tailed maggot hemolymph with the concentration of 25-30 µg /100 µl and 35-40 µg / 100 µl, respectively are enough to kill Escherichia coli and Salmonella typhimurium, respectively. Our ndings corroborated with earlier studies, identi ed the role of normal hemolymphs to kill different kinds of bacteria (Sahalan et al, 2006;Basseri et al, 2016;Hirsch et al, 2020;Lee et al, 2020).…”

A bioinformatic study of antimicrobial peptides identified in the Black Soldier Fly (BSF) Hermetia illucens (Diptera: Stratiomyidae)

“…The immune system of the insect H. illucens is very developed, as this species feeds on decaying substrates and manure, which are extremely rich in pathogenic microorganisms, as it possible to observe also in other species, such as in Eristalis tenax . Twenty-two AMPs were indeed identified in the Diptera E. tenax , that has been able to adapt to different aquatic habitats (sewage tanks and manure pits) with heavy microbial load 29 . AMPs, which are synthesized by the fat body and hemocytes and then secreted into the hemolymph, are an essential part of the immune defense 30 , 31 .…”

Microbial Stress Resistance of Eristalis tenax Rat-Tailed Maggots

“…However, vitro induction to immune transcripts in Eristalis tenax maggots was performed by and followed by Hirsch et al, (2020). identified thirty novel genes of E. tenax that were induced in response to septic injury including novel putative AMPs.…”

“…identified thirty novel genes of E. tenax that were induced in response to septic injury including novel putative AMPs. Hirsch et al, (2020) tested the antibacterial activity under simulated physiological conditions, a bacterial lipopolysaccharide was injected into Eristalis tenax maggots to enhance immunity-related AMPs that are synthesized in response to the injection, they are identified twenty-two AMPs and selected nine for larger-scale synthesis to test their activity against multidrugresistant Gram-negative bacteria. A diptericin-like peptide (EtDip) and two cecropin-like peptides (EtCec1-a and EtCec2-a) displayed strong activity against the pathogens.…”