The Silkworm as a Source of Natural Antimicrobial Preparations: Efficacy on Various Bacterial Strains

Abstract

The global spread of multi-resistant pathogens responsible for infections, which cannot be treated with existing drugs such as antibiotics, is of particular concern. Antibiotics are becoming increasingly ineffective and drug resistance is leading to more difficult-to-treat infections; therefore, new bioactive compounds with antimicrobial activity are needed and new alternative sources should be found. Antimicrobial peptides (AMPs) are synthesized by processes typical of the innate immune system and are present in almost all organisms. Insects are extremely resistant to bacterial infections as they can produce a wide range of AMPs, providing an effective first line of defense. The AMPs produced by insects therefore represent a possible source of natural antimicrobial molecules. In this paper, the possibility of using plasma preparations from silkworm (Bombyx mori) larvae as a source of antimicrobials was evaluated. After simple purification steps, insect plasma was analyzed and tested on different Gram-positive and Gram-negative bacterial strains. The results obtained are encouraging as the assays on Escherichia coli and Enterobacter cloacae showed significant decrease in the growth of these Gram-negative bacteria. Similar results were obtained on Gram-positive bacteria, such as Micrococcus luteus and Bacillus subtilis, which showed strong susceptibility to the silkworm AMPs pool. In contrast, Staphylococcus aureus displayed high resistance to Bombyx mori plasma. Finally, the tested plasma formulations were assessed for possible storage not only at 4 °C, but also above room temperature. In conclusion, partially purified plasma from silkworm could be a promising source of AMPs which could be used in formulations for topical applications, without additional and expensive purification steps.

Nutritional Composition, Health Benefits, and Application Value of Edible Insects: A Review

“…For example, papain peptides isolated from swallowtail butterflies ( Papilio xuthus ) have broad activity against fungal, gram-positive, and gram-negative bacteria and no hemolytic activity against human red blood cells [ 200 ]. Antimicrobial peptides purified from the plasma of silkworm ( Bombyx mori ) larvae were found to have a significant growth inhibitory effect on different Gram-positive and Gram-negative strains of bacteria, which led to the use of antimicrobial peptides from silkworm larvae as an alternative to antibiotic treatment in this study [ 201 ]. Eight peptides purified from the lymphatic blood of the greater wax moth ( Galleria mellonella ) were also examined for their antibacterial activity.…”