Evaluation of the antibacterial potential of black soldier fly larvae (Hermetia illucens) extracts against escherichia coli and staphylococcus aureus.

Abstract

Globally, there has been an increase in antibacterial drug resistance hence a lot of research has been geared to developing alternatives to combat the challenge. Insects such as Black Soldier Fly Larvae (BSFL) have been cited to have the potential to reduce bacterial loads. Therefore, this study was carried out to evaluate the antibacterial potential of BSFL extracts against gram-negative and gram-positive bacteria, and standard strains of E. coli and S. aureus were used respectively. This was an experimental study that involved sampling four farms (labelled A, B, C and D) that were commercially growing BSFL and feeding their BSFL on substrates of varying compositions. The BSFL samples from these four farms were extracted in two states that is to say the fresh and dried BSFL. To evaluate for pharmacological effects, two solvents were used in the extraction of the BSFL, and these were distilled water and analytical methanol. A single concentration of 0.5 g/ml (500 mg/ml) for all the extracts (aqueous and methanol extracts) was used to test for antibacterial activity against the two bacteria species. The antibacterial potential was determined by antimicrobial methods such as agar well diffusion (zones of inhibition), Resazurin-based turbidometric assay, MIC and MBC. All the results were analyzed using SPSS version 22, and descriptive statistics were used to obtain the mean and standard error means of the required variables such as zones of inhibition, MICs and MBCs. T-tests and ANOVA were used to compare variables across different groups at a 5% level of significance. It was observed that aqueous extracts from fresh BSFL obtained from farm C had activity(4.75±2.48) against E. coli. It was also observed that all extracts (aqueous and methanol) from the four farms had activity against S. aureus except for aqueous extracts that were extracted from dry BSFL that did not show activity. Therefore, it could be concluded that the BSFL extracts could be used as candidates for antibacterial substances.