Antibacterial effect of extracts ofHermetia illucens(Diptera: Stratiomyidae) larvae against Gram-negative bacteria : Hermetia illucensantibacterial activity

Black soldier flies, Hermetia illucens L., are a common colonizer of animal wastes. However, all published development data for this species are from studies using artificial diets. This study represents the first examining black soldier fly development on animal wastes. Additionally, this study examined the ability of black soldier fly larvae to reduce dry matter and associated nutrients in manure. Black soldier fly larvae were fed four rates of dairy manure to determine their effects on larval and adult life history traits. Feed rate affected larval and adult development. Those fed less ration daily weighed less than those fed a greater ration. Additionally, larvae provided the least amount of dairy manure took longer to develop to the prepupal stage; however, they needed less time to reach the adult stage. Adults resulting from larvae provided 27 g dairy manure/d lived 3-4 d less than those fed 70 g dairy manure. Percentage survivorship to the prepupal or adult stages did not differ across treatments. Larvae fed 27 g dairy manure daily reduced manure dry matter mass by 58%, whereas those fed 70 g daily reduced dry matter 33%. Black soldier fly larvae were able to reduce available P by 61-70% and N by 30-50% across treatments. Based on results from this study, the black soldier fly could be used to reduce wastes and associated nutrients in confined bovine facilities.

Maggot therapy is a simple and highly successful method for cleansing infected and necrotic wounds. The use of maggots has become increasingly important in the treatment of non-healing wounds, particularly those infected with the multidrug-resistant pathogen, methicillin-resistant Staphylococcus aureus (MRSA). The increasing challenge concerning the treatment of MRSA infections and the recent finding of vancomycin-resistant strains of MRSA have elicited the search for novel antibacterial compounds and, in particular, investigations into the potent antibacterial mechanism(s) behind maggot therapy. In this study, we report that excretions/secretions (ES) from the blowfly, Lucilia sericata, exhibit potent, thermally stable, protease resistant antibacterial activity against MRSA in vitro. We describe the initial characterisation of two antibacterial factors from native ES of L. sericata. A small, <500 Da factor with significant antibacterial activity against MRSA was partially isolated using ultrafiltration techniques. The potent activity of this factor was comparable to that of native excretions/secretions. A larger, 0.5-3-kDa factor with significant activity against S. aureus was also partially characterised.

Lucilia sericata maggots are successfully used for treating chronic wounds. As the healing process in these wounds is complicated by bacteria, particularly when residing in biofilms that protect them from antibiotics and the immune system, we assessed the effects of maggot excretions/secretions (ES) on Staphylococcus aureus and Pseudomonas aeruginosa biofilms, the clinically most relevant species. We assessed the effects of ES on biofilms using microtitre plate assays, on bacterial viability using in vitro killing and radial diffusion assays, and on quorum sensing systems using specific reporter bacteria. As little as 0.2 microg of ES prevented S. aureus biofilm formation and 2 microg of ES rapidly degraded biofilms. In contrast, ES initially promoted P. aeruginosa biofilm formation, but after 10 h the biofilms collapsed. Degradation of P. aeruginosa biofilms started after 10 h and required 10-fold more ES than S. aureus biofilms. Boiling of ES abrogated their effects on S. aureus, but not on P. aeruginosa, biofilms, indicating that different molecules within ES are responsible for the observed effects. Modulation of biofilms by ES did not involve bacterial killing or effects on quorum sensing systems. Maggot ES are differentially effective against biofilms of S. aureus and P. aeruginosa.