A metagenomic assessment of the bacteria associated with Lucilia sericata and Lucilia cuprina (Diptera: Calliphoridae)

Endotoxin testing of a wound debridement device containing medicinal Lucilia sericata larvae

Alimentary products of medicinal Lucilia sericata larvae are studied to determine their mechanisms of action, particularly in the contexts of wound debridement and disinfection. Furthermore, the larvae can be applied to patients in contained medical devices (such as the BioBag; BioMonde). Here, we tested the materials and larval content of the most commonly used debridement device (the "BB-50") to explore the possibility that endotoxins may be contributing to the bio-activity of the product, given that endotoxins are potent stimulants of cellular activation. Using standardised protocols to collect larval alimentary products (LAP), we proceeded to determine residual endotoxin levels in LAP derived from the device, before and after the neutralisation of interfering enzymatic activity. The debridement device and its associated larval content was not a significant source of lipopolysaccharide (LPS) activity. However, it is clear from these experiments that a failure to remove the confounding serine proteinase activity would have resulted in spuriously high and erroneous results. The residual LPS levels detected are unlikely to be active in wound healing assays, following cross-referencing to publications where LPS at much higher levels has been shown to have positive and negative effects on processes associated with wound repair and tissue regeneration.

Insect Artifacts Are More than Just Altered Bloodstains

The bases for forensic entomology are that insects and their arthropod relatives can serve as evidence in criminal, medical and civil legal matters. However, some of the very same species that provide utility to legal investigations can also complicate crime scenes by distorting existing body fluid evidence (e.g., bloodstains, semen, saliva) and/or depositing artifacts derived from the insect alimentary canal at primary or secondary crime scenes. The insect contaminants are referred to as insect stains, artifacts, specks or spots, and are most commonly associated with human bloodstains. This review will discuss the different types of insect artifacts that have been described from crime scenes and laboratory experiments, as well as examine insect contaminates (non-blood based artifacts, transfer patterns, meconium, and larval fluids) that have received little research or case attention. Methods currently used for distinguishing insect stains from human body fluids will also be discussed and compared to presumptive tests used for identification of human body fluids. Since all available methods have severe limitations, areas of new research will be identified for the purpose of development of diagnostic techniques for detection of insect artifacts.

Bacterial Communities Associated with Houseflies (Musca domestica L.) Sampled within and between Farms

The housefly feeds and reproduces in animal manure and decaying organic substances and thus lives in intimate association with various microorganisms including human pathogens. In order to understand the variation and association between bacteria and the housefly, we used 16S rRNA gene amplicon sequencing to describe bacterial communities of 90 individual houseflies collected within and between ten dairy farms in Denmark. Analysis of gene sequences showed that the most abundant classes of bacteria found across all sites included Bacilli, Clostridia, Actinobacteria, Flavobacteria, and all classes of Proteobacteria and at the genus level the most abundant genera included Corynebacterium, Lactobacillus, Staphylococcus, Vagococcus, Weissella, Lactococcus, and Aerococcus. Comparison of the microbiota of houseflies revealed a highly diverse microbiota compared to other insect species and with most variation in species richness and diversity found between individuals, but not locations. Our study is the first in-depth amplicon sequencing study of the housefly microbiota, and collectively shows that the microbiota of single houseflies is highly diverse and differs between individuals likely to reflect the lifestyle of the housefly. We suggest that these results should be taken into account when addressing the transmission of pathogens by the housefly and assessing the vector competence variation under natural conditions.

Safety aspects of the production of foods and food ingredients from insects

At present, insects are rarely used by the European food industry, but they are a subject of growing interest as an alternative source of raw materials. The risks associated with the use of insects in the production of foods and food ingredients have not been sufficiently investigated. There is a lack of scientifically based knowledge of insect processing to ensure food safety, especially when these processes are carried out on an industrial scale. This review focuses on the safety aspects that need to be considered regarding the fractionation of insects for the production of foods and food ingredients.

Significance and Roles of Proteus spp. Bacteria in Natural Environments

Proteus spp. bacteria were first described in 1885 by Gustav Hauser, who had revealed their feature of intensive swarming growth. Currently, the genus is divided into Proteus mirabilis, Proteus vulgaris, Proteus penneri, Proteus hauseri, and three unnamed genomospecies 4, 5, and 6 and consists of 80 O-antigenic serogroups. The bacteria are known to be human opportunistic pathogens, isolated from urine, wounds, and other clinical sources. It is postulated that intestines are a reservoir of these proteolytic organisms. Many wild and domestic animals may be hosts of Proteus spp. bacteria, which are commonly known to play a role of parasites or commensals. However, interesting examples of their symbiotic relationships with higher organisms have also been described. Proteus spp. bacteria present in soil or water habitats are often regarded as indicators of fecal pollution, posing a threat of poisoning when the contaminated water or seafood is consumed. The health risk may also be connected with drug-resistant strains sourcing from intestines. Positive aspects of the bacteria presence in water and soil are connected with exceptional features displayed by autochthonic Proteus spp. strains detected in these environments. These rods acquire various metabolic abilities allowing their adaptation to different environmental conditions, such as high concentrations of heavy metals or toxic substances, which may be exploited as sources of energy and nutrition by the bacteria. The Proteus spp. abilities to tolerate or utilize polluting compounds as well as promote plant growth provide a possibility of employing these microorganisms in bioremediation and environmental protection.

Genome Sequence of a Proteus mirabilis Strain Isolated from the Salivary Glands of Larval Lucilia sericata

We announce a draft genome sequence of a Proteus mirabilis strain derived from Lucilia sericata salivary glands. This strain is demonstrated to attract and induce oviposition by L. sericata, a common blow fly important to medicine, agriculture, and forensics. The genome sequence will help dissect interkingdom communication between the species.

A case of Ignatzschineria bacteraemia in an unconscious man from the Netherlands

Introduction:

Ignatzschineria species were previously known as Schineria species and are well known inhabitants of the larvae of the parasitic fly Wohlfahrtia magnifica.

Case presentation:

We report a case of Ignatzschineria species bacteraemia in a Dutch patient with a wound infested with maggots.

Conclusion:

In the past, these bacteria have been isolated from Wohlfahrtia magnifica, a fly not indigenous to The Netherlands. Other fly larvae such as the blowfly larvae probably infested the wound and harboured this Ignatzschineria strain which subsequently caused this bacteraemia. A two-week course of amoxicillin/clavulanic acid was given with good clinical response.

Towards next generation maggot debridement therapy: transgenic Lucilia sericata larvae that produce and secrete a human growth factor

BACKGROUND

Diabetes and its concurrent complications impact a significant proportion of the population of the US and create a large financial burden on the American health care system. FDA-approved maggot debridement therapy (MDT), the application of sterile laboratory-reared Lucilia sericata (green bottle fly) larvae to wounds, is a cost-effective and successful treatment for diabetic foot ulcers and other medical conditions. Human platelet derived growth factor-BB (PDGF-BB) is a secreted dimeric peptide growth factor that binds the PDGF receptor. PDGF-BB stimulates cell proliferation and survival, promotes wound healing, and has been investigated as a possible topical treatment for non-healing wounds. Genetic engineering has allowed for expression and secretion of human growth factors and other proteins in transgenic insects. Here, we present a novel concept in MDT technology that combines the established benefits of MDT with the power of genetic engineering to promote healing. The focus of this study is to create and characterize strains of transgenic L. sericata that express and secrete PDGF-BB at detectable levels in adult hemolymph, whole larval lysate, and maggot excretions/ secretions (ES), with potential for clinical utility in wound healing.

RESULTS

We have engineered and confirmed transgene insertion in several strains of L. sericata that express human PDGF-BB. Using a heat-inducible promoter to control the pdgf-b gene, pdgf-b mRNA was detected via semi-quantitative PCR upon heat shock. PDGF-BB protein was also detectable in larval lysates and adult hemolymph but not larval ES. An alternative, tetracycline-repressible pdgf-b system mediated expression of pdgf-b mRNA when maggots were raised on diet that lacked tetracycline. Further, PDGF-BB protein was readily detected in whole larval lysate as well as larval ES.

CONCLUSIONS

Here we show robust, inducible expression and production of human PDGF-BB protein from two conditional expression systems in transgenic L. sericata larvae. The tetracycline-repressible system appears to be the most promising as PDGF-BB protein was detectable in larval ES following induction. Our system could potentially be used to deliver a variety of growth factors and anti-microbial peptides to the wound environment with the aim of enhancing wound healing, thereby improving patient outcome in a cost-effective manner.

Microbial ecology of the salmon necrobiome: evidence salmon carrion decomposition influences aquatic and terrestrial insect microbiomes

Carrion decomposition is driven by complex relationships that affect necrobiome community (i.e. all organisms and their genes associated with a dead animal) interactions, such as insect species arrival time to carrion and microbial succession. Little is understood about how microbial communities interact with invertebrates at the aquatic-terrestrial habitat interface. The first objective of the study was to characterize internal microbial communities using high-throughput sequencing of 16S rRNA gene amplicons for aquatic insects (three mayfly species) in streams with salmon carcasses compared with those in streams without salmon carcasses. The second objective was to assess the epinecrotic microbial communities of decomposing salmon carcasses (Oncorhynchus keta) compared with those of terrestrial necrophagous insects (Calliphora terraenovae larvae and adults) associated with the carcasses. There was a significant difference in the internal microbiomes of mayflies collected in salmon carcass-bearing streams and in non-carcass streams, while the developmental stage of blow flies was the governing factor in structuring necrophagous insect internal microbiota. Furthermore, the necrophagous internal microbiome was influenced by the resource on which the larvae developed, and changes in the adult microbiome varied temporally. Overall, these carrion subsidy-driven networks respond to resource pulses with bottom-up effects on consumer microbial structure, as revealed by shifting communities over space and time.

Agricultural applications of insect ecological genomics

Agricultural entomology is poised to benefit from the application of ecological genomics, particularly the fields of biofuels generation and pest control. Metagenomic methods can characterize microbial communities of termites, wood-boring beetles and livestock pests, and transcriptomic approaches reveal molecular bases behind wood-digesting capabilities of these insects, leading to potential mechanisms for biofuel generation. Genome sequences are being exploited to develop new pest control methods, identify candidate antigens to vaccinate livestock, and discover RNAi target sequences and potential non-target effects in other insects. Gene content analyses of pest genome sequences and their endosymbionts suggest metabolic interdependencies between organisms, exposing potential gene targets for insect control. Finally, genome-wide association studies and genotyping by high-throughput sequencing promise to improve management of pesticide resistance.

Dynamics of Necrophagous Insect and Tissue Bacteria for Postmortem Interval Estimation During the Warm Season in Romania

The estimation of postmortem interval (PMI) is affected by several factors including the cause of death, the place where the body lay after death, and the weather conditions during decomposition. Given the climatic differences among biogeographic locations, the understanding of necrophagous insect species biology and ecology is required when estimating PMI. The current experimental model was developed in Romania during the warm season in an outdoor location. The aim of the study was to identify the necrophagous insect species diversity and dynamics, and to detect the bacterial species present during decomposition in order to determine if their presence or incidence timing could be useful to estimate PMI. The decomposition process of domestic swine carcasses was monitored throughout a 14-wk period (10 July-10 October 2013), along with a daily record of meteorological parameters. The chronological succession of necrophagous entomofauna comprised nine Diptera species, with the dominant presence of Chrysomya albiceps (Wiedemann 1819) (Calliphoridae), while only two Coleoptera species were identified, Dermestes undulatus (L. 1758) and Creophilus maxillosus Brahm 1970. The bacterial diversity and dynamics from the mouth and rectum tissues, and third-instar dipteran larvae were identified using denaturing gradient gel electrophoresis analysis and sequencing of bacterial 16S rRNA gene fragments. Throughout the decomposition process, two main bacterial chronological groups were differentiated, represented by Firmicutes and Gammaproteobacteria. Twenty-six taxa from the rectal cavity and 22 from the mouth cavity were identified, with the dominant phylum in both these cavities corresponding to Firmicutes. The present data strengthen the postmortem entomological and microbial information for the warm season in this temperate-continental area, as well as the role of microbes in carcass decomposition.

Effects of Floral Scent, Color and Pollen on Foraging Decisions and Oocyte Development of Common Green Bottle Flies

The common green bottle fly Lucilia sericata (Meigen) and other filth flies frequently visit pollen-rich composite flowers such as the Oxeye daisy, Leucanthemum vulgare Lam. In laboratory experiments with L. sericata, we investigated the effect of generic floral scent and color cues, and of Oxeye daisy-specific cues, on foraging decisions by recently eclosed flies. We also tested the effect of a floral pollen diet with 0–35% moisture content on the ability of females to mature their oocytes. Our data indicate that (1) young flies in the presence of generic floral scent respond more strongly to a uniformly yellow cue than to any other uniform color cue (green, white, black, blue, red) except for ultraviolet (UV); (2) the floral scent of Oxeye daisies enhances the attractiveness of a yellow cue; and (3) moisture-rich pollen provides nutrients that facilitate ovary maturation of flies. With evidence that L. sericata exploits floral cues during foraging, and that pollen can be an alternate protein source to animal feces and carrion, Pollen apparently plays a major role in the foraging ecology of L. sericata and possibly other filth flies. These flies, in turn, may play a significant role as pollinators, as supported by a recently published study.