A novel approach to the antimicrobial activity of maggot debridement therapy

Abstract

ObjectivesCommercially produced sterile green bottle fly Lucilia sericata maggots are successfully employed by practitioners worldwide to clean a multitude of chronic necrotic wounds and reduce wound bacterial burdens during maggot debridement therapy (MDT). Secretions from the maggots exhibit antimicrobial activity along with other activities beneficial for wound healing. With the rise of multidrug-resistant bacteria, new approaches to identifying the active compounds responsible for the antimicrobial activity within this treatment are imperative. Therefore, the aim of this study was to use a novel approach to investigate the output of secreted proteins from the maggots under conditions mimicking clinical treatments.MethodscDNA libraries constructed from microdissected salivary glands and whole maggots, respectively, were treated with transposon-assisted signal trapping (TAST), a technique selecting for the identification of secreted proteins. Several putative secreted components of insect immunity were identified, including a defensin named lucifensin, which was produced recombinantly as a Trx-fusion protein in Escherichia coli, purified using immobilized metal affinity chromatography and reverse-phase HPLC, and tested in vitro against Gram-positive and Gram-negative bacterial strains.ResultsLucifensin was active against Staphylococcus carnosus, Streptococcus pyogenes and Streptococcus pneumoniae (MIC 2 mg/L), as well as Staphylococcus aureus (MIC 16 mg/L). The peptide did not show antimicrobial activity towards Gram-negative bacteria. The MIC of lucifensin for the methicillin-resistant S. aureus and glycopeptide-intermediate S. aureus isolates tested ranged from 8 to >128 mg/L.ConclusionsThe TAST results did not reveal any highly secreted compounds with putative antimicrobial activity, implying an alternative antimicrobial activity of MDT. Lucifensin showed antimicrobial activities comparable to other defensins and could have potential as a future drug candidate scaffold, for redesign for other applications besides the topical treatment of infected wounds.

Lucifensin, a Novel Insect Defensin of Medicinal Maggots: Synthesis and Structural Study

“…[16] Later, the production of recombinant peptide resulting in a few milligrams of active peptide was reported by Andersen. [17] Although, numerous synthetic studies in the expanding field of defensins have been published during the last two decades, only a few of these papers report the synthesis of insect defensins. [24,27,28] Despite the generally accepted assumption that the synthesis and purification of a 40-residue peptide can be achieved routinely, the synthesis of a peptide with multiple disulfide bridges is not so straightforward.…”

“…This was also reported by Andersen et al in his recent study on lucifensin. [17] As shown in Table 1, the lucifensin analogues that folded through one disulfide bridge were practically inactive even against the most sensitive bacteria, M. luteus and B. subtilis. The only exception is the Luc[C16-C36] analogue, which still shows noticeable activity as clearly demonstrated by the drop-diffusion assay on a Petri dish (Figure 7 A).…”

“…of lucifensin was also published by Andersen and co-workers. [17] They had used molecular biology methods to confirm its sequence. We assume lucifensin to be the key antimicrobial component that protects the maggots when they are exposed to the highly infectious environment of a wound during maggot therapy, and that it contributes as a disinfectant and healing factor.…”

Insect proteins as a potential source of antimicrobial peptides in livestock production. A review

“…Maggots eat necrotic tissues and contribute to the process of wound healing via a number of mechanisms. After ingestion of the necrotic tissue, their secretions promote fibroblast aggregation and tissue repairment, and finally they release antimicrobial peptides which inhibit bacterial growth in the wound (Bulet et al, 2004;Andersen et al, 2010;Ratcliffe et al, 2011).…”

In vitro antimicrobial activity of maggot excretions/secretions of Sarcophaga (Liopygia) argyrostoma (Robineau-Desvoidy)

“…The importance of the maggot's ES is not only limited to their killing powers against several bacterial strains, but also to the factors which are contributing to the cleaning of infected wounds. Altincicek and Vilcinskas (2009) and Andersen et al (2010) mentioned that L. sericata has 65 immune-inducible genes including lysozyme-and transferrin-likegenes and 3 proline-rich AMPs. Proteases induced by larval secretions may play a crucial role in wound healing process.…”