Evaluation of the Antimicrobial Activity of an Extract of Lactobacillus casei-Infected Hermetia illucens Larvae Produced Using an Automatic Injection System.

Kyu-Shik Lee,Tae-Won Goo,Eun-Young Yun

doi:10.3390/ani10112121

Kyu-Shik Lee, Tae-Won Goo + Show 1 more

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https://doi.org/10.3390/ani10112121

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Abstract

Simple SummaryIn this investigation, an automatic mass-injection system was developed to produce an extract of Lactobacillus casei–infected Hermetia illucens larvae (HIL) at low cost. The extract produced was found to be a novel natural antibiotic candidate with a wide range of applications, especially in the food, animal feed, and medicinal industries.In the present study, we developed an automatic mass-injection system (AMIS) to produce an extract of infected H. illucens larvae (iHIL-E) and then evaluated antimicrobial peptide (AMP) expressions and assessed the antimicrobial activity of iHIL-E against various pathogens and Lactobacillus species. AMP gene expressions were assessed by real-time quantitative polymerase chain reaction (PCR) and the antimicrobial activities of iHIL-E were estimated using a radial diffusion assay and by determining minimal inhibitory concentrations. Results showed that the antimicrobial activity of HIL extract was effectively enhanced by L. casei infection and that the gene expressions of cecropin 3 and defensin 3 (antimicrobial peptides) were up-regulated. iHIL-E also prevented the growths of Enterococcus faecalis, Streptococcus mutans, and Candida vaginitis (MICs 200, 500, and 1000 µg/100 µL, respectively) and demonstrated high protease resistance. Moreover, the growths of methicillin-resistant Staphylococcus aureus, antibiotic-resistant Pseudomonas aeruginosa and AMP-resistant bacteria, Serratia marcescens, and Pseudomons tolaasii were significantly suppressed by iHIL-E. In addition, although iHIL completely cleared Salmonella species at concentrations of >200 µg/100 µL, Lactobacillus species were unaffected by iHIL at concentrations of <1000 µg/100 µL. The present investigation shows that the devised automatic mass injection system is effective for the mass production of the extract of infected HIL and that this extract is a novel, natural, protease-resistant, antibiotic candidate with broad-spectrum antibiotic activity.

Highlights

Antibiotics play important roles in human and livestock health as they effectively treat and prevent infectious diseases caused by pathogens
When L. casei were injected by manual method into H. illucens larvae (HIL), induced antimicrobial activities were observed in 86.1% of HIL extracts (Figure S1)
We evaluated whether the gene expressions of antimicrobial peptide (AMP) were induced by L. casei infection and found HiCec3 and HiDef3 gene expressions were dramatically enhanced by injection (Figure 2)

Summary

Introduction

Antibiotics play important roles in human and livestock health as they effectively treat and prevent infectious diseases caused by pathogens. The overuse and abuse of antibiotics in feed has caused many problems, such as the evolution of antibiotic-resistant bacteria, the presence of antibiotic residues in livestock products, weakening of disease resistance among livestock, and environmental pollution caused by antibiotic residues in excretions [1,2,3]. After recognizing the seriousness of the problems caused by antibiotic overuse and abuse, the European Union completely banned the use of in-feed antibiotics for growth promotion in 2006. Novel natural antibiotics are being considered as a potential means of overcoming the problems associated with the overuse and abuse of antibiotics and chemical preservatives [4,5]

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