Bacterial proximity effects on the transfer of antibiotic resistance genes within the alimentary tract of yellow mealworm larvae

The arthropod intestinal tract and other anatomical parts naturally carry microorganisms. Some of which are pathogens, secrete toxins, or carry transferable antibiotic-resistance genes. The risks associated with the production and consumption of edible arthropods are dependent on indigenous microbes, as well as microbes introduced during the processes of rearing. This mass arthropod production puts individual arthropods in close proximity, which increases the possibility of their exposure to antibiotic-resistant bacteria carried by bacteria from fellow insects, industry workers, or rearing hardware and substrates. The purpose of this study was to determine if the alimentary tract of the yellow mealworm provided an environment permitting horizontal gene transfer between bacteria. The effect of the concentration of bacterial exposure was also assessed. Antibiotic resistance gene transfer between marker Salmonella Lignières (Enterobacterales: Enterobacteriaceae) and Escherichia coli (Migula) (Enterobacterales: Enterobacteriaceae) introduced into the larval gut demonstrated that the nutrient-rich environment of the yellow mealworm gut provided favorable conditions for the transfer of antibiotic resistance genes. Conjugation frequencies were similar across inoculum concentrations; however, transconjugant production correlated positively to increased exposure concentration. The lowest concentration of bacterial exposure required enrichment to detect and thus may have been approaching a threshold level for the 2 bacteria to colocate within the expanse of the larval gut. While many factors can affect this transfer, the simple factor of the proximity of donor and recipient bacteria, as defined by the concentration of bacteria within the volume of the insect gut, likely primarily contributed to the efficiency of antibiotic gene transfer.

The bacterial and archaeal communities of flies, manure, lagoons, and troughs at a working dairy

Background

Fundamental investigations into the location, load, and persistence of microbes, whether beneficial or detrimental, are scarce. Many questions about the retention and survival of microbes on various surfaces, as well as the load necessary for spread, exist. To answer these questions, we must know more about where to find various microbes and in what concentrations, the composition of the microbial communities, and the extent of dissemination between various elements. This study investigated the diversity, composition, and relative abundance of the communities associated with manure, lagoons, troughs, house flies, and stable flies present at a dairy, implementing two different free-stall management systems: flow-through and cross-vent. Shotgun metagenomics at the community level was used to compare the microbiomes within the dairy, allowing confident interpretation at the species level.

Results

The results showed that there were significant difference in microbial composition between not only each of the dairy elements but also management styles. The primary exceptions were the microbiomes of the house fly and the stable fly. Their compositions heavily overlapped with one another, but interestingly, not with the other components sampled. Additionally, both species of flies carried more pathogens than the other elements of the dairy, indicating that they may not share these organisms with the other components, or that the environments offered by the other components are unsatisfactory for the survival of some pathogens..

Conclusion

The lack of overlapping pathogen profiles suggests a lack of transfer from flies to other dairy elements. Dairy health data, showing a low incidence of disease, suggests minimal sharing of bacteria by the flies at a level required for infection, given the health program of this dairy. While flies did carry a multitude of pathogenic bacteria, the mere presence of the bacteria associated with the flies did not necessarily translate into high risk leading to morbidity and mortality at this dairy. Thus, using flies as the sole sentinel of dairy health may not be appropriate for all bacterial pathogens or dairies.

Assessment of Potential Anti-Methanogenic and Antimicrobial Activity of Ethyl Nitroacetate, α-Lipoic Acid, Taurine and L-Cysteinesulfinic Acid In Vitro

Livestock producers need new technologies to maintain the optimal health and well-being of their animals while minimizing the risks of propagating and disseminating pathogenic and antimicrobial-resistant bacteria to humans or other animals. Where possible, these interventions should contribute to the efficiency and profitability of animal production to avoid passing costs on to consumers. In this study, we examined the potential of nitroethane, 3-nitro-1-propionate, ethyl nitroacetate, taurine and L-cysteinesulfinic acid to modulate rumen methane production, a digestive inefficiency that results in the loss of up to 12% of the host's dietary energy intake and a major contributor of methane as a greenhouse gas to the atmosphere. The potential for these compounds to inhibit the foodborne pathogens, Escherichia coli O157:H7 and Salmonella Typhimurium DT104, was also tested. The results from the present study revealed that anaerobically grown O157:H7 and DT104 treated with the methanogenic inhibitor, ethyl nitroacetate, at concentrations of 3 and 9 mM had decreased (p < 0.05) mean specific growth rates of O157:H7 (by 22 to 36%) and of DT104 (by 16 to 26%) when compared to controls (0.823 and 0.886 h-1, respectively). The growth rates of O157:H7 and DT104 were decreased (p < 0.05) from controls by 31 to 73% and by 41 to 78% by α-lipoic acid, which we also found to inhibit in vitro rumen methanogenesis up to 66% (p < 0.05). Ethyl nitroacetate was mainly bacteriostatic, whereas 9 mM α-lipoic acid decreased (p < 0.05) maximal optical densities (measured at 600 nm) of O157:H7 and DT104 by 25 and 42% compared to controls (0.448 and 0.451, respectively). In the present study, the other oxidized nitro and organosulfur compounds were neither antimicrobial nor anti-methanogenic.

Chlortetracycline Concentration Impact on Salmonella Typhimurium Sustainability in the Presence of Porcine Gastrointestinal Tract Bacteria Maintained in Continuous Culture

Concern exists that the continued use of antibiotics in animal feeds may lead to an increased prevalence of resistant bacteria within the host animal's gastrointestinal tract. To evaluate the effect of chlortetracycline on the persistence of Salmonella enterica serotype Typhimurium within a diverse population of porcine cecal bacteria, we cultured a mixed population of cecal bacteria without or with added chlortetracycline. When grown at a 24 h vessel turnover rate, chlortetracycline-susceptible S. Typhimurium exhibited more than 2.5 times faster (p < 0.05) disappearance rates than theoretically expected (0.301 log10 colony-forming unit/mL per day) but did not differ whether treated or not with 55 mg of chlortetracycline/L. Chlortetracycline-resistant S. Typhimurium was not recovered from any of these cultures. When the mixed cultures were inoculated with a chlortetracycline-resistant S. Typhimurium, rates of disappearance were nearly two times slower (p < 0.05) than those observed earlier with chlortetracycline-susceptible S. Typhimurium, and cultures persisted at >2 log10 colony-forming units/mL for up to 14 days of treatment with 110 mg of chlortetracycline/L. Under the conditions of this study, chlortetracycline-resistant S. Typhimurium was competitively enabled to persist longer within the mixed populations of porcine gut bacteria than chlortetracycline-susceptible S. Typhimurium, regardless of the presence or absence of added chlortetracycline.

Campylobacter jejuni Response When Inoculated in Bovine In Vitro Fecal Microbial Consortia Incubations in the Presence of Metabolic Inhibitors

Infection with the foodborne pathogen Campylobacter is the leading bacterial cause of human foodborne illness in the United States. The objectives of this experiment were to test the hypothesis that mixed microbial populations from the bovine rumen may be better at excluding Campylobacter than populations from freshly voided feces and to explore potential reasons as to why the rumen may be a less favorable environment for Campylobacter than feces. In an initial experiment, C. jejuni cultures inoculated without or with freshly collected bovine rumen fluid, bovine feces or their combination were cultured micro-aerobically for 48 h. Results revealed that C. jejuni grew at similar growth rates during the first 6 h of incubation regardless of whether inoculated with the rumen or fecal contents, with rates ranging from 0.178 to 0.222 h-1. However, C. jejuni counts (log10 colony-forming units/mL) at the end of the 48 h incubation were lowest in cultures inoculated with rumen fluid (5.73 log10 CFUs/mL), intermediate in cultures inoculated with feces or both feces and rumen fluid (7.16 and 6.36 log10 CFUs/mL) and highest in pure culture controls that had not been inoculated with the rumen or fecal contents (8.32 log10 CFUs/mL). In follow-up experiments intended to examine the potential effects of hydrogen and hydrogen-consuming methanogens on C. jejuni, freshly collected bovine feces, suspended in anaerobic buffer, were incubated anaerobically under either a 100% carbon dioxide or 50:50 carbon dioxide/hydrogen gas mix. While C. jejuni viability decreased <1 log10 CFUs/mL during incubation of the fecal suspensions, this did not differ whether under low or high hydrogen accumulations or whether the suspensions were treated without or with the mechanistically distinct methanogen inhibitors, 5 mM nitrate, 0.05 mM 2-bromosulfonate or 0.001 mM monensin. These results suggest that little if any competition between C. jejuni and hydrogen-consuming methanogens exists in the bovine intestine based on fecal incubations.

Survival of Campylobacter jejuni during in vitro culture with mixed bovine ruminal microorganisms in the presence of methanogen inhibitors

Foodborne pathogen Campylobacter jejuni has been associated with ruminants. The objectives of this experiment were to determine C. jejuni survivability in mixed in vitro rumen microbial populations and the impact on methane production with or without methane inhibitors 2-bromosulfonate (BES) and/or sodium nitrate. When inoculated into rumen microbial populations without or with 0.5 mM BES, 5.0 mM nitrate or their combination, C. jejuni viability decreased from 4.7 ± 0.1 log10 colony forming units (CFU)/mL after 24 h. Loss of C. jejuni viability was greater (P < 0.05) when incubated under 100% CO2 compared to 50% H2:50% CO2, decreasing 1.46 versus 1.15 log units, respectively. C. jejuni viability was also decreased (P < 0.05) by more than 0.43 log units by the anti-methanogen treatments. Rumen microbial populations produced less methane (P = 0.05) when incubated with than without C. jejuni regardless of whether under 100% CO2 or 50% H2:50% CO2. For either gas phase, nitrate was decreased (13.2 versus 37.9%) by the anti-methanogen treatments versus controls although not always significant. C. jejuni-inoculated populations metabolized 16.4% more (P < 0.05) nitrate under H2:CO2 versus 100% CO2. Apparently, C. jejuni can compete for H2 with methanogens but has limited survivability under rumen conditions.

Behavioral interplay between mosquito and mycolactone produced by Mycobacterium ulcerans and bacterial gene expression induced by mosquito proximity

Mycolactone is a cytotoxic lipid metabolite produced by Mycobacterium ulcerans, the environmental pathogen responsible for Buruli ulcer, a neglected tropical disease. Mycobacterium ulcerans is prevalent in West Africa, particularly found in lentic environments, where mosquitoes also occur. Researchers hypothesize mosquitoes could serve as a transmission mechanism resulting in infection by M. ulcerans when mosquitoes pierce skin contaminated with M. ulcerans. The interplay between the pathogen, mycolactone, and mosquito is only just beginning to be explored. A triple-choice assay was conducted to determine the host-seeking preference of Aedes aegypti between M. ulcerans wildtype (MU, mycolactone active) and mutant (MUlac-, mycolactone inactive). Both qualitative and quantitative differences in volatile organic compounds' (VOCs) profiles of MU and MUlac- were determined by GC-MS. Additionally, we evaluated the interplay between Ae. aegypti proximity and M. ulcerans mRNA expression. The results showed that mosquito attraction was significantly greater (126.0%) to an artificial host treated with MU than MUlac-. We found that MU and MUlac produced differential profiles of VOCs associated with a wide range of biological importance from quorum sensing (QS) to human odor components. RT-qPCR assays showed that mycolactone upregulation was 24-fold greater for MU exposed to Ae. aegypti in direct proximity. Transcriptome data indicated significant induction of ten chromosomal genes of MU involved in stress responses and membrane protein, compared to MUlac- when directly having access to or in near mosquito proximity. Our study provides evidence of possible interkingdom interactions between unicellular and multicellular species that MU present on human skin is capable of interreacting with unrelated species (i.e., mosquitoes), altering its gene expression when mosquitoes are in direct contact or proximity, potentially impacting the production of its VOCs, and consequently leading to the stronger attraction of mosquitoes toward human hosts. This study elucidates interkingdom interactions between viable M. ulcerans bacteria and Ae. aegypti mosquitoes, which rarely have been explored in the past. Our finding opens new doors for future research in terms of disease ecology, prevalence, and pathogen dispersal outside of the M. ulcerans system.

Quorum sensing gene regulation in Staphylococcus epidermidis reduces the attraction of Aedes aegypti (L.) (Diptera: Culicidae)

Introduction

Identifying mechanisms regulating mosquito attraction to hosts is key to suppressing pathogen transmission. Historically, the ecology of the host microbial community and its influence on mosquito attraction, specifically, whether bacterial communication through quorum sensing (QS) modulates VOC production that affects mosquito behavior have not been extensively considered.

Methods

Behavioral choice assays were applied along with volatile collection, followed by GC-MS and RNA transcriptome analyses of bacteria with and without a quorum-sensing inhibitor, furanone C-30.

Results

Utilizing the quorum-sensing inhibitor on a skin-inhabiting bacterium, Staphylococcus epidermidis, we disrupted its interkingdom communication with adult Aedes aegypti and mitigated their attraction to a blood-meal by 55.1%.

Discussion

One potential mechanism suppressing mosquito attraction could be the reduction (31.6% in our study) of bacterial volatiles and their associated concentrations by shifting S. epidermidis metabolic (12 of 29 up regulated genes) and stress (5 of 36 down regulated genes) responses. Manipulating the quorum-sensing pathways could serve as a mechanism to reduce mosquito attraction to a host. Such manipulations could be developed into novel control methods for pathogen-transmitting mosquitoes and other arthropods.

Management Practices Affecting Lesser Mealworm Larvae (Alphitobius diaperinus) Associated Microbial Community in a Broiler House and After Relocating With the Litter Into Pastureland

Lesser mealworms are often found infesting production houses used to raise broiler chickens. Previous studies have investigated pathogenic microorganisms associated with the larvae, but a more thorough study relating total microbiome changes due to management procedures and flock rotations was needed. Additionally, there is a question of what microbiota are transferred into the environment when the litter, in which larvae reside, is piled in pastureland for use as fertilizer and where interactions with the soil and other fauna can occur. This study chronicled, by the 16S rRNA sequencing, the bacterial community profile of larvae in a broiler grow-out house synchronizing to when birds were added to and removed from the house over 2.5 years. The profile was found to be relatively constant despite 11 flock rotations and management disruptions, specifically litter cleanout procedures and the addition of new birds or bedding. In contrast, once removed from the controlled broiler house environment and placed into open pastureland, the substantial microbial diversity brought with the larvae showed greater fluctuation in structure with environmental conditions, one of which was rainfall. Surprisingly, these larvae survived at least 19 weeks, so the potential for moving larval-associated microbes into the environment needs further assessment to minimize the risk of relocating foodborne pathogens and also to assess those bacteria-generating metabolites that have benefits to plant growth when using the litter as a fertilizer. The characterization of their microbiome is the first step to investigating the influences of their microbes on the manmade and environmental ecosystems.

Gene expression in Lucilia sericata (Diptera: Calliphoridae) larvae exposed to Pseudomonas aeruginosa and Acinetobacter baumannii identifies shared and microbe-specific induction of immune genes

Antibiotic resistance is a continuing challenge in medicine. There are various strategies for expanding antibiotic therapeutic repertoires, including the use of blow flies. Their larvae exhibit strong antibiotic and antibiofilm properties that alter microbiome communities. One species, Lucilia sericata, is used to treat problematic wounds due to its debridement capabilities and its excretions and secretions that kill some pathogenic bacteria. There is much to be learned about how L. sericata interacts with microbiomes at the molecular level. To address this deficiency, gene expression was assessed after feeding exposure (1 h or 4 h) to two clinically problematic pathogens: Pseudomonas aeruginosa and Acinetobacter baumannii. The results identified immunity-related genes that were differentially expressed when exposed to these pathogens, as well as non-immune genes possibly involved in gut responses to bacterial infection. There was a greater response to P. aeruginosa that increased over time, while few genes responded to A. baumannii exposure, and expression was not time-dependent. The response to feeding on pathogens indicates a few common responses and features distinct to each pathogen, which is useful in improving the wound debridement therapy and helps to develop biomimetic alternatives.

Adult Alphitobius diaperinus Microbial Community during Broiler Production and in Spent Litter after Stockpiling

The facilities used to raise broiler chickens are often infested with litter beetles (lesser mealworm, Alphitobius diaperinus). These beetles have been studied for their carriage of pathogenic microbes; however, a more comprehensive microbiome study on these arthropods is lacking. This study investigated their microbial community in a longitudinal study throughout 2.5 years of poultry production and after the spent litter, containing the mealworms, was piled in pastureland for use as fertilizer. The mean most abundant phyla harbored by the beetles in house were the Proteobacteria (39.8%), then Firmicutes (30.8%), Actinobacteria (21.1%), Tenericutes (5.1%), and Bacteroidetes (1.6%). The community showed a modest decrease in Firmicutes and increase in Proteobacteria over successive flock rotations. The beetles were relocated within the spent litter to pastureland, where they were found at least 19 weeks later. Over time in the pastureland, their microbial profile underwent a large decrease in the percent of Firmicutes (20.5%). The lesser mealworm showed an ability to survive long-term in the open environment within the spent litter, where their microbiome should be further assessed to both reduce the risk of transferring harmful bacteria, as well as to enhance their contribution when the litter is used as a fertilizer.

Disinfectant and Antimicrobial Susceptibility Studies of Staphylococcus aureus Strains and ST398-MRSA and ST5-MRSA Strains from Swine Mandibular Lymph Node Tissue, Commercial Pork Sausage Meat and Swine Feces

Staphylococcus aureus (S. aureus) causes gastrointestinal illness worldwide. Disinfectants are used throughout the food chain for pathogenic bacteria control. We investigated S. aureus bioavailability in swine Mandibular lymph node tissue (MLT) and pork sausage meat (PSM), established susceptibility values for S. aureus to disinfectants, and determined the multilocus sequence type of MRSA strains. Antimicrobial and disinfectant susceptibility profiles were determined for 164 S. aureus strains isolated from swine feces (n = 63), MLT (n = 49) and PSM (n = 52). No antimicrobial resistance (AMR) was detected to daptomycin, nitrofurantoin, linezolid, and tigecycline, while high AMR prevalence was determined to erythromycin (50.6%), tylosin tartrate (42.7%), penicillin (72%), and tetracycline (68.9%). Methicillin-resistant S. aureus (MRSA) strains, ST398 (n = 6) and ST5 (n = 1), were found in the MLT and PSM, 4 MRSA in MLT and 3 MRSA strains in the PSM. About 17.5% of feces strains and 41.6% of MLT and PSM strains were resistant to chlorhexidine. All strains were susceptible to triclosan and benzalkonium chloride, with no cross-resistance between antimicrobials and disinfectants. Six MRSA strains had elevated susceptibilities to 18 disinfectants. The use of formaldehyde and tris(hydroxylmethyl)nitromethane in DC&R was not effective, which can add chemicals to the environment. Didecyldimethylammonium chloride and benzyldimethylhexadecylammonium chloride were equally effective disinfectants. ST398 and ST5 MRSA strains had elevated susceptibilities to 75% of the disinfectants tested. This study establishes susceptibility values for S. aureus strains from swine feces, mandibular lymph node tissue, and commercial pork sausage against 24 disinfectants. Since it was demonstrated that S. aureus and MRSA strains can be found deep within swine lymph node tissue, it may be beneficial for the consumer if raw swine lymph node tissue is not used in uncooked food products and pork sausage.

Antagonistic Effects of Lipids Against the Anti-Escherichia coli and Anti-Salmonella Activity of Thymol and Thymol-β-d-Glucopyranoside in Porcine Gut and Fecal Cultures In Vitro

Strategies are sought to reduce the carriage and dissemination of zoonotic pathogens and antimicrobial-resistant microbes within food-producing animals and their production environment. Thymol (an essential oil) is a potent bactericide in vitro but in vivo efficacy has been inconsistent, largely due to its lipophilicity and absorption, which limits its passage and subsequent availability in the distal gastrointestinal tract. Conjugation of thymol to glucose to form thymol-β-d-glucopyranoside can decrease its absorption, but in vivo passage of effective concentrations to the lower gut remains suboptimal. Considering that contemporary swine diets often contain 5% or more added fat (to increase caloric density and reduce dustiness), we hypothesized that there may be sufficient residual fat in the distal intestinal tract to sequester free or conjugated thymol, thereby limiting the availability and subsequent effectiveness of this biocide. In support of this hypothesis, the anti-Salmonella Typhimurium effects of 6 mM free or conjugated thymol, expressed as log₁₀-fold reductions of colony-forming units (CFU) ml^-1, were diminished 90 and 58%, respectively, following 24-h in vitro anaerobic fecal incubation (at 39°C) with 3% added vegetable oil compared to reductions achieved during culture without added oil (6.1 log₁₀ CFU ml^-1). The antagonistic effect of vegetable oil and the bactericidal effect of free and conjugated thymol against Escherichia coli K88 tested similarly were diminished 86 and 84%, respectively, compared to reductions achieved in cultures incubated without added vegetable oil (5.7 log₁₀ CFU ml^-1). Inclusion of taurine (8 mg/ml), bile acids (0.6 mg/ml), or emulsifiers such as polyoxyethylene-40 stearate (0.2%), Tween 20, or Tween 80 (each at 1%) in the in vitro incubations had little effect on vegetable oil-caused inhibition of free or conjugated thymol. Based on these results, it seems reasonable to suspect that undigested lipid in the distal gut may limit the effectiveness of free or conjugated thymol. Accordingly, additional research is warranted to learn how to overcome obstacles diminishing bactericidal activity of free and conjugated thymol in the lower gastrointestinal tract of food-producing animals.

Black soldier fly, Hermetia illucens (L.) (Diptera: Stratiomyidae), and house fly, Musca domestica L. (Diptera: Muscidae), larvae reduce livestock manure and possibly associated nutrients: An assessment at two scales

The industrial production of insects for waste management or as a protein source is becoming vital to our society. Large volumes of manure are produced by concentrated animal facilities around the globe that must be managed, utilized, and disposed of properly. Flies offer a partial solution with their abilities to reduce these wastes and heavy metal pollutants. Meat and crop proteins are being supplemented by insect proteins for many feeds across the globe, yet science-based studies behind the mass-rearing of insects are still in their infancy. In the current study, the percent change in the composition of nutrients, heavy metals, and fiber, in dairy, poultry, and swine manure degraded by either black soldier fly (BSF) or house fly (HF) larvae was explored. Pre-digested and post-digested manure samples were collected from four independent studies that differed in production scale (number of larvae and feeding regimen): 1) BSF small-scale (100 larvae fed incrementally), 2) HF small-scale (100 larvae fed incrementally), 3) BSF large-scale (10,000 larvae fed a single time), and 4) HF large-scale (4,000 larvae fed a single time). Results indicate that nitrogen is a key nutrient impacted by larval digestion of manure by both species, regardless of scale. However, scale significantly impacted reductions of other nutrients, as did the type of manure in which the insects were reared. Ultimately, this study demonstrated that manure type and rearing scale impact the ability of BSF and HF larvae to reduce nutrients and heavy metals in manure, and thus insect management procedures need to be congruent with production emphases of the insects for waste management or protein products. Failure to take scale into consideration could lead to inaccurate assumptions related to industrialized efforts on this topic.

Poultry litter and the environment: Microbial profile of litter during successive flock rotations and after spreading on pastureland

With the increasing demand for broiler meat, a thorough evaluation of the microbial community within the broiler houses and sites where litter is deposited is critical to animal and environmental wellbeing. However not much is known in this arena, so our work evaluates the litter bacterial microbial community within a house over a 2.5 year period through 11 flock rotations, a partial and a total cleanout, and the subsequent deposition of the litter as fertilizer on pastureland. The effects of both time and management practices correlated with alterations of the litter microbial community. The cleanout practices and introduction of new bedding had minimal influence on the house microbial community once it was established, which generally showed a consistent increase in the proportion of Actinobacteria and a decrease in Firmicutes over the 11 flock rotations. Analysis of the bacterial profile at the genus level gave increased resolution, revealing changes during the first and second flock rotation and after the total cleanout. The disturbance of the partial cleanout seemed to be buffered by the supporting conditions within the house while the total cleanout showed a small, but significant influence. The pastureland deposition of litter, however, was affected by time and abiotic factors that changed the litter microbial community structure weekly. The stockpiled litter had an increase in the phyla Actinobacteria and the class Bacilli that commonly have microbes utilizing nitrogen and decaying materials, in comparison to Native soil. Further, the soil beneath where the litter was stored for 20 weeks, lost diversity, indicating a possible effect of the litter stockpiling on environmental quality at that site. How management practices affect the composition of the microbial community within the litter of the broiler house is of interest in terms of bird health and environmentally for future utilization of spent litter.

Reduced Environmental Microbial Diversity on the Cuticle and in the Galleries of a Subterranean Termite Compared to Surrounding Soil

Termites are intimately tied to the microbial world, as they utilize their gut microbiome for the conversion of plant cellulose into necessary nutrients. Subterranean termites must also protect themselves from the vast diversity of harmful microbes found in soil. However, not all soil microbes are harmful, such as Streptomyces and methanotrophic bacteria that some species of termites harbor in complex nest structures made of fecal material. The eastern subterranean termite, Reticulitermes flavipes, has a simple nest structure consisting of fecal lined galleries. We tested the hypothesis that R. flavipes maintains a select microbial community in its nests to limit the penetration of harmful soilborne pathogens and favor the growth of beneficial microbes. Using Illumina sequencing, we characterized the bacterial and fungal communities in the surrounding soil, in the nest galleries, and on the cuticle of workers. We found that the galleries provide a more beneficial microbial community than the surrounding soil. Bacterial and fungal diversity was highest in the soil, lower in the galleries, and least on the cuticle. Bacterial communities clustered together according to the substrate from which they were sampled, but this clustering was less clear in fungal communities. Most of the identified bacterial and fungal taxa were unique to one substrate, but the soil and gallery communities had very similar phylum-level taxonomic profiles. Notably, the galleries of R. flavipes also harbored both the potentially beneficial Streptomyces and the methanotrophic Methylacidiphilales, indicating that these microbial associations in fecal material pre-date the emergence of complex fecal nest structures. Surprisingly, several pathogenic groups were relatively abundant in the galleries and on the cuticle, suggesting that pathogens may accumulate within termite nests over time while putatively remaining at enzootic level during the lifetime of the colony.

Inhibition of Salmonella Binding to Porcine Intestinal Cells by a Wood-Derived Prebiotic

Numerous Salmonellaenterica serovars can cause disease and contamination of animal-produced foods. Oligosaccharide-rich products capable of blocking pathogen adherence to intestinal mucosa are attractive alternatives to antibiotics as these have potential to prevent enteric infections. Presently, a wood-derived prebiotic composed mainly of glucose-galactose-mannose-xylose oligomers was found to inhibit mannose-sensitive binding of select SalmonellaTyphimurium and Escherichia coli strains when reacted with Saccharomyces boulardii. Tests for the ability of the prebiotic to prevent binding of a green fluorescent protein (GFP)-labeled S.Typhimurium to intestinal porcine epithelial cells (IPEC-J2) cultured in vitro revealed that prebiotic-exposed GFP-labeled S.Typhimurium bound > 30% fewer individual IPEC-J2 cells than did GFP-labeled S.Typhimurium having no prebiotic exposure. Quantitatively, 90% fewer prebiotic-exposed GFP-labeled S.Typhimurium cells were bound per individual IPEC-J2 cell compared to non-prebiotic exposed GFP-labeled S.Typhimurium. Comparison of invasiveness of S.Typhimurium DT104 against IPEC-J2 cells revealed greater than a 90% decrease in intracellular recovery of prebiotic-exposed S.Typhimurium DT104 compared to non-exposed controls (averaging 4.4 ± 0.2 log₁₀ CFU/well). These results suggest compounds within the wood-derived prebiotic bound to E. coli and S.Typhimurium-produced adhesions and in the case of S.Typhimurium, this adhesion-binding activity inhibited the binding and invasion of IPEC-J2 cells.

How Management Practices Within a Poultry House During Successive Flock Rotations Change the Structure of the Soil Microbiome

The microbiome within a poultry production house influences the attainment of physiologically strong birds and thus food safety and public health. Yet little is known about the microbial communities within the house and the effects on the soil microbes onto which the houses are placed; nor the effects of management practices on their equilibrium. This study looked at the soil bacterial microbiome before a broiler house was constructed, then through 11 flock rotations (2.5 years) that included a partial clean-out and a total clean-out within the management regimen. Major shifts were observed, occurring at the taxonomic class level, related to the introduction of bedding and birds on top of the soil. The partial clean-out of litter did not change the soil bacterial community in any substantial way, only prompting a temporary increase in some genera; however, the total litter clean-out caused a major increase in a cohort of Actinobacteria. The underlying soil contained bacteria beneficial for poultry metabolism, such as Lactobacillus, Faecalibacterium, Bacteriodes, and Ruminococcus. Additionally, management practices affected the class structure of the soil bacterial community beneath the poultry house. The scheduling of these practices should be leveraged to exploit maintenance of beneficial bacteria that maximize microbiome contributions to bird production processes, while minimizing possible antibiotic-resistant bacteria and environmental effects.

Inhibition and Interactions of Campylobacter jejuni from Broiler Chicken Houses with Organic Acids

Campylobacter jejuni is a bacterium that causes major diarrheal disease worldwide and is also one of the top five foodborne pathogens encountered in the United States. Poultry is a major source of C. jejuni, and a high-risk factor for contracting campylobacteriosis. Organic acids are used in the United States during food animal processing for removal of bacterial contamination from animal carcasses. Six organic acids were evaluated in inhibition studies of 96 C. jejuni strains obtained from shoe covers used in broiler chicken houses at different poultry farms in several states by determining the susceptibilities of the C. jejuni strains, along with the pH values at the molar minimum inhibitory concentrations (MICMs). The undissociated and dissociated organic acid concentrations were calculated at the MICMs with the Henderson-Hasselbalch equation. The results for the 96 C. jejuni strains were treated similarly for each different organic acid. Campylobacter jejuni inhibition did correlate with the dissociated organic acids, but did not correlate with pH or with the undissociated organic acids. When the concentrations of dissociated organic acids decreased, the C. jejuni strains were not disinfected. A carcass wash using organic acids should have the concentration of dissociated acid species carefully controlled. It is suggested to maintain a dissociated acid concentration for propionic, l-lactic, formic, citric, butyric, and acetic acids at 24, 40, 36, 21, 23, and 25 mM, respectively, and at these dissociated organic acid levels an acid wash would be expected to remove or inhibit 97% or more of the C. jejuni bacteria studied here. However, studies must be undertaken to confirm that the suggested concentrations of dissociated organic acids are adequate to remove C. jejuni bacteria in the field vs. the laboratory. Due to propionate, l-lactate, formate, butyrate, and acetate being utilized by C. jejuni, these organic acids may not be appropriate for use as a carcass wash to remove C. jejuni surface contamination. Of all tested organic acids, dissociated citric acid was the most efficient at inhibiting C. jejuni.

Interactions of organic acids with vancomycin-resistant Enterococcus faecium isolated from community wastewater in Texas

AIMS

Investigate the interactions of organic acids (OAs), acetic, butyric, citric, formic, lactic and propionic acid against 50 Gram-positive vancomycin-resistant Enterococcus faecium (VRE) strains to determine whether pH, undissociated or dissociated acid forms correlate with bacterial inhibition.

METHODS AND RESULTS

Concentrations of undissociated and dissociated OAs at the molar minimum inhibitory concentrations (MIC_M s) of the VRE were calculated using the Henderson-Hasselbalch equation. The pH at the MIC_M s of all VRE strains against acetic, butyric, formic and propionic acids was similar, 4·66 ± 0·07, but there was a 1·1 pH unit difference for all six OAs. Inhibition of VRE by all six OAs did not appear to be solely dependent on pH or on the undissociated OA species. The inhibition of VRE by all six dissociated acids was within Δ = 3·1 mmol l^-1 .

CONCLUSIONS

Vancomycin-resistant Enterococcus faecium inhibition correlated with the dissociated OA species. A small decrease in the concentration of the dissociated OAs from optimum may result in allowing VRE strains to escape disinfection.

SIGNIFICANCE AND IMPACT OF THE STUDY

When an OA is used to disinfect VRE strains, the concentration of the dissociated OA should be carefully controlled. A concentration of at least 20 mmol l^-1 dissociated OA should be maintained when disinfecting VRE.

Interactions of organic acids with Campylobacter coli from swine

Campylobacter coli is a bacterial species that is a major cause of diarrheal disease worldwide, and Campylobacter spp. are among the top 5 foodborne pathogens in the United States. During food production organic acids (OAs) are often used to remove bacteria from animal carcasses. The interactions of six OAs with 111 C. coli strains obtained from swine and retail pork chops were studied by determining the molar minimum inhibitory concentrations (MICMs) of the C. coli strains, and the pH at the MICMs. The Henderson-Hasselbalch equation was used to calculate the concentrations of the undissociated and dissociated OAs at the MICMs of the C. coli strains. The results for the 111 different C. coli strains obtained from different locations were treated as a single group for each OA since many of the C. coli strains behaved similarly to each different OA. Inhibition of C. coli was not dependent on pH or on the undissociated OA species, but C. coli inhibition correlated with the dissociated OA species. Therefore, if the concentration of the dissociated OAs decreases from optimum, one may then expect that C. coli bacteria would escape disinfection. The concentration of the dissociated OA should be carefully controlled in a carcass wash. We suggest maintaining a concentration of the dissociated acetic, butyric, citric, formic, lactic and propionic acids at 29, 23, 11, 35, 22 and 25 mM, respectively, when using a carcass wash with these OAs to remove C. coli bacteria. However, due to C. coli utilization of acetate, formate, lactate and propionate, these four OAs may not be the best choice to use for a carcass wash to remove C. coli contamination. Of the six OAs, citric acid was the most efficient at inhibiting C. coli.

Nigella sativa L. as an alternative antibiotic feed supplement and effect on growth performance in weanling pigs

BACKGROUND

Nigella sativa L. (NS) is a plant containing bioactive constituents such as thymoquinone. Extracts of NS improve performance and reduce enteropathogen colonization in poultry and small ruminants, but studies with swine are lacking. In two different studies oral administration of NS extracts at doses equivalent to 0, 1.5 and 4.5 g kg^-1 diet was assessed on piglet performance and intestinal carriage of wildtype Escherichia coli and Campylobacter, and Salmonella Typhimurium.

RESULTS

Wildtype E. coli populations in the jejunal and rectal content collected 9 days after treatment began were decreased (P ≤ 0.05). Populations recovered from pigs treated with extract at 1.5 and 4.5 g kg^-1 diet were 0.72-1.31 log₁₀ units lower than the controls (ranging from 6.05 to 6.61 log₁₀ CFU g^-1 ). Wildtype Campylobacter and Salmonella Typhimurium were unaffected by NS treatment. Feed efficiency over the 9 days improved linearly (P < 0.05) from 3.88 with 0 NS-treated pigs to 1.47 and 1.41 with pigs treated with NS at 1.5 and 4.5 g kg^-1 diet, respectively, possibly due to high glutamine/glutamic acid content of the NS extract.

CONCLUSION

NS supplementation of weanling pigs improved feed efficiency and helped control intestinal E. coli during this vulnerable production phase. © 2017 Society of Chemical Industry.

Larval digestion of different manure types by the black soldier fly (Diptera: Stratiomyidae) impacts associated volatile emissions

Volatile emissions from decomposing animal waste are known environmental pollutants. The black soldier fly, Hermetia illucens (L.), is being evaluated for industrialization as a means to recycle wastes and produce protein for use as food and feed. We examined the ability of black soldier fly larvae to reduce odorous compounds associated with animal wastes. Black soldier fly larvae were reared under laboratory conditions on poultry, swine, and dairy manure at feed rates of 18.0 and 27.0 g every other day until 40% reached the prepupal stage. Volatile emissions were collected and analyzed from freshly thawed as well as the digested waste when 90% of the black soldier fly larvae reached the prepupal stage. Volatiles were also collected simultaneously from manure not inoculated with black soldier fly larvae (non-digested) and held under similar conditions. Manure samples were analyzed for relative amounts of nine select odorous volatile organic compounds: phenol, 4-methylphenol, indole, 3-methylindole, propanoic acid, 2-methylpropanoic acid, butanoic acid, 3-methylbutanoic acid and pentanoic acid. Black soldier fly larvae reduced emissions of all volatile organic compounds by 87% or greater. Complete reductions were observed for 2-methly propanoic acid in digested poultry manure, phenol, 4-methylphenol, indole and all five fatty acids in digested swine manure, and 4-methylphenol, indole, 3-methylindole and all five acids in digested dairy manure. This study is the first to identify volatile emissions from manure digested by black soldier fly larvae and compare to those found in non-digested manure. These data demonstrate additional benefits of using black soldier fly larvae as a cost-effective and environmentally friendly means of livestock manure management in comparison to current methods.

CAPSULE

Black soldier fly larvae are capable of altering the overall profile of volatile organic compounds and reducing levels of targeted odorous compounds in livestock manure.

Temporal and Spatial Impact of Human Cadaver Decomposition on Soil Bacterial and Arthropod Community Structure and Function

As vertebrate carrion decomposes, there is a release of nutrient-rich fluids into the underlying soil, which can impact associated biological community structure and function. How these changes alter soil biogeochemical cycles is relatively unknown and may prove useful in the identification of carrion decomposition islands that have long lasting, focal ecological effects. This study investigated the spatial (0, 1, and 5 m) and temporal (3-732 days) dynamics of human cadaver decomposition on soil bacterial and arthropod community structure and microbial function. We observed strong evidence of a predictable response to cadaver decomposition that varies over space for soil bacterial and arthropod community structure, carbon (C) mineralization and microbial substrate utilization patterns. In the presence of a cadaver (i.e., 0 m samples), the relative abundance of Bacteroidetes and Firmicutes was greater, while the relative abundance of Acidobacteria, Chloroflexi, Gemmatimonadetes, and Verrucomicrobia was lower when compared to samples at 1 and 5 m. Micro-arthropods were more abundant (15 to 17-fold) in soils collected at 0 m compared to either 1 or 5 m, but overall, micro-arthropod community composition was unrelated to either bacterial community composition or function. Bacterial community structure and microbial function also exhibited temporal relationships, whereas arthropod community structure did not. Cumulative precipitation was more effective in predicting temporal variations in bacterial abundance and microbial activity than accumulated degree days. In the presence of the cadaver (i.e., 0 m samples), the relative abundance of Actinobacteria increased significantly with cumulative precipitation. Furthermore, soil bacterial communities and C mineralization were sensitive to the introduction of human cadavers as they diverged from baseline levels and did not recover completely in approximately 2 years. These data are valuable for understanding ecosystem function surrounding carrion decomposition islands and can be applicable to environmental bio-monitoring and forensic sciences.

The horizontal transfer of Salmonella between the lesser mealworm (Alphitobius diaperinus) and poultry manure

There is need to determine the nature of enduring reservoirs of Salmonella contributing to perpetual contamination within poultry flocks. The dispersal of Salmonella between birds, litter and the lesser mealworm has been established, but the extent that these act as critical components in the epidemiology of Salmonella infection during broiler grow-out and flock rotation has not been delineated; in particular, the level of participation by the lesser mealworm beetles (LMB) as agents of retention and dispersal. This study defines this route of transmission and provides empirical data on bacterial loads that facilitate Salmonella transfer. Results showed differential Salmonella transfer dependent on bacterial concentration. At 10³  cfu/ml, only a small, but not significant, amount of Salmonella was transferred, from the LMB to the manure and back to uninfected LMB; while from 10⁵ to 10⁷  cfu/ml, a significant acquisition and transfer occurred both internally and externally to the LMB over 4 and 24 hr exposures. These data will be used in correlation with facility management practices to develop intervention strategies to mitigate the establishment and spreading of reservoir Salmonella populations contributing to pre-harvest contamination of poultry flocks.

Evaluation of Sterilized Artificial Diets for Mass Rearing the Lucilia sericata (Diptera: Calliphoridae)

The impact of six sterilized diets (blood-yeast agar diet, decomposed beef liver diet, powdered beef liver diet, powdered fish diet, milk-based diet, and a chemically defined diet) on Lucilia sericata (Meigen) larvae reared at three densities (10 larvae, 20 larvae, and 40 larvae on 20 g diet) was determined in comparison to fresh beef liver as a control. Specifically, the effects of these diets on the following traits of L. sericata were measured: 1) pupal weight, 2) pupation percentage, 3) eclosion percentage, as well as 4) adult longevity. The experiment included two trials with five technical replicates in each. Lucilia sericata did not successfully develop on the powdered fish, milk-based, or chemically defined diets. Overall, the liver-based diets (decomposed and powdered) resulted in the most similar fly development to the fresh beef liver. Larvae reared on blood-yeast agar diet resulted in a significantly (increased 20.56% ± 8.09%) greater pupation rate than those reared on the decomposed and powdered beef liver diets. Pupae from larvae fed the fresh beef liver were significantly larger (6.27 ± 1.01 mg, 4.05 ± 0.94 mg larger, respectively) than those reared on the blood-yeast agar diet, decomposed beef liver, and powdered beef liver diets. Overall, results revealed larvae reared on sterilized liver-based diets resulted in traits similar to those raised on fresh beef liver. Owing to low costs the sterile liver-based diets could be produced and used with limited infrastructure and economic incomes.

Nonconsumptive Effects of Predatory Chrysomya rufifacies (Diptera: Calliphoridae) Larval Cues on Larval Cochliomyia macellaria (Diptera: Calliphoridae) Growth and Development

Forensic entomologists often rely on development data associated with a given species to estimate when it colonized human or other vertebrate remains. In most instances, these development studies are based on single species reared in isolation in the laboratory. This study examined the impact of excretions and secretions (ES) associated with third-instar Chrysomya rufifacies (Macquart), a predator, on the development of its prey, Cochliomyia macellaria (F.). Not surprisingly, Ch. rufifacies ES did not impact the development of first- or second-instar C. macellaria, which are typically not preyed on by Ch. rufifacies. However, development of third-instar C. macellaria, which do experience predation, was impacted. First, larvae were longer than those in the control (deionized water, dH2O). Filtering the ES and removing the associated bacteria and byproducts >0.2 µm dampened the previous impact observed by the unfiltered ES on third-instar C. macellaria. Second, third-instar C. macellaria treated with unfiltered ES completed pupariation 8 h quicker than the controls. Filtering the ES lessened this effect by 50%. And finally, third-instar C. macellaria treated with filtered or unfiltered Ch. rufifacies ES reached adulthood ∼5 h faster than controls treated with dH2O. In summary, these data have large ramifications for forensic entomology, as multiple species being present on decomposing remains is not uncommon. Understanding the impact of associated ES produced by interspecific cohorts on associated development could lead to more precise estimates of the minimum postmortem interval for forensic investigation of decomposing remains.

Susceptibility of Alphitobius diaperinus in Texas to permethrin- and β-cyfluthrin-treated surfaces

BACKGROUND

Effective control of the lesser mealworm beetle, Alphitobius diaperinus, relies heavily on insecticides. The susceptibility level of beetles to these insecticides can be dependent on active ingredient, population treated, formulation, surface treated and timing of observation. The susceptibility of adult beetles from six populations to β-cyfluthrin was determined up to 48 h after exposure. The susceptibility of adult beetles to the label rate of β-cyfluthrin and permethrin formulations on concrete, wood-chip-type particle board and pressure-treated wood was determined up to 48 h post-exposure.

RESULTS

Variation in LC₅₀ values at 2 and 24 h was found within and between beetle populations from two regions of Texas. The permethrin formulation had lower mean mortality than the β-cyfluthrin formulation on all surfaces tested. The permethrin formulation had high levels of recovery on all surfaces tested after 2 h. Surface affected the efficacy of the insecticides tested on killing adult beetles.

CONCLUSION

Permethrin-based insecticide had lower knockdown and persistence on various surfaces over time than β-cyfluthrin-based insecticide. Beetle recovery in less susceptible populations may necessitate longer observation periods for efficacy evaluations. Our study also shows that surfaces chosen can affect the efficacy of the compound on killing adult beetles. © 2016 Society of Chemical Industry.

Disinfectant and Antimicrobial Susceptibility Profiles of the Big Six Non-O157 Shiga Toxin-Producing Escherichia coli Strains from Food Animals and Humans

The disinfectant and antimicrobial susceptibility profiles of 138 non-O157 Shiga toxin-producing Escherichia coli strains (STECs) from food animals and humans were determined. Antimicrobial resistance (AMR) was moderate (39.1% of strains) in response to 15 antimicrobial agents. Animal strains had a lower AMR prevalence (35.6%) than did human strains (43.9%) but a higher prevalence of the resistance profile GEN-KAN-TET. A decreasing prevalence of AMR was found among animal strains from serogroups O45 > O145 > O121 > O111 > O26 > O103 and among human strains from serogroups O145 > O103 > O26 > O111 > O121 > O45. One animal strain from serogroups O121 and O145 and one human strain from serogroup O26 had extensive drug resistance. A high prevalence of AMR in animal O45 and O121 strains and no resistance or a low prevalence of resistance in human strains from these serogroups suggests a source other than food animals for human exposure to these strains. Among the 24 disinfectants evaluated, all strains were susceptible to triclosan. Animal strains had a higher prevalence of resistance to chlorhexidine than did human strains. Both animal and human strains had a similar low prevalence of low-level benzalkonium chloride resistance, and animal and human strains had similar susceptibility profiles for most other disinfectants. Benzyldimethylammonium chlorides and C10AC were the primary active components in disinfectants DC&R and P-128, respectively, against non-O157 STECs. A disinfectant FS512 MIC ≥ 8 μg/ml was more prevalent among animal O121 strains (61.5%) than among human O121 strains (25%), which may also suggest a source of human exposure to STEC O121 other than food animals. Bacterial inhibition was not dependent solely on pH but was correlated with the presence of dissociated organic acid species and some undissociated acids.

Poultry litter and the environment: Physiochemical properties of litter and soil during successive flock rotations and after remote site deposition

The U.S. broiler meat market has grown over the past 16 years and destinations for U.S. broiler meat exports expanded to over 150 countries. This market opportunity has spurred a corresponding increase in industrialized poultry production, which due to the confined space in which high numbers of animals are housed, risks accumulating nutrients and pollutants. The purpose of this research was to determine the level of pollutants within poultry litter and the underlying soil within a production facility; and to explore the impact of spent litter deposition into the environment. The study follows a production facility for the first 2.5 years of production. It monitors the effects of successive flocks and management practices on 15 physiochemical parameters: Ca, Cu, electrical conductivity, Fe, K, Mg, Mn, moisture, Na, NO3(-)/N, organic matter, P, pH, S, and Zn. Litter samples were collected in-house, after clean-outs and during stockpiling. The soil before house placement, after the clean-outs and following litter stockpiling was monitored. Management practices markedly altered the physiochemical profiles of the litter in-house. A canonical discriminant analysis was used to describe the relationship between the parameters and sampling times. The litter profiles grouped into five clusters corresponding to time and management practices. The soil in-house exhibited mean increases in all physiochemical parameters (2-297 fold) except Fe, Mg, %M, and pH. The spent litter was followed after deposition onto a field for use as fertilizer. After 20 weeks, the soil beneath the litter exhibited increases in EC, Cu, K, Na, NO3(-)/N, %OM, P, S and Zn; while %M decreased. Understanding the impacts of industrialized poultry farms on the environment is vital as the cumulative ecological impact of this land usage could be substantial if not properly managed to reduce the risk of potential pollutant infiltration into the environment.

Effect of Quorum Sensing by Staphylococcus epidermidis on the Attraction Response of Female Adult Yellow Fever Mosquitoes, Aedes aegypti aegypti (Linnaeus) (Diptera: Culicidae), to a Blood-Feeding Source

Aedes aegypti, the principal vector of yellow fever and dengue fever, is responsible for more than 30,000 deaths annually. Compounds such as carbon dioxide, amino acids, fatty acids and other volatile organic compounds (VOCs) have been widely studied for their role in attracting Ae. aegypti to hosts. Many VOCs from humans are produced by associated skin microbiota. Staphyloccocus epidermidis, although not the most abundant bacteria according to surveys of relative 16S ribosomal RNA abundance, commonly occurs on human skin. Bacteria demonstrate population level decision-making through quorum sensing. Many quorum sensing molecules, such as indole, volatilize and become part of the host odor plum. To date, no one has directly demonstrated the link between quorum sensing (i.e., decision-making) by bacteria associated with a host as a factor regulating arthropod vector attraction. This study examined this specific question with regards to S. epidermidis and Ae. aegypti. Pairwise tests were conducted to examine the response of female Ae. aegypti to combinations of tryptic soy broth (TSB) and S. epidermidis wildtype and agr- strains. The agr gene expresses an accessory gene regulator for quorum sensing; therefore, removing this gene inhibits quorum sensing of the bacteria. Differential attractiveness of mosquitoes to the wildtype and agr- strains was observed. Both wildtype and the agr- strain of S. epidermidis with TSB were marginally more attractive to Ae. aegypti than the TSB alone. Most interestingly, the blood-feeder treated with wildtype S. epidermidis/TSB attracted 74% of Ae. aegypti compared to the agr- strain of S. epidermidis/TSB (P ≤ 0.0001). This study is the first to suggest a role for interkingdom communication between host symbiotic bacteria and mosquitoes. This may have implications for mosquito decision-making with regards to host detection, location and acceptance. We speculate that mosquitoes "eavesdrop" on the chemical discussions occurring between host-associated microbes to determine suitability for blood feeding. We believe these data suggest that manipulating quorum sensing by bacteria could serve as a novel approach for reducing mosquito attraction to hosts, or possibly enhancing the trapping of adults at favored oviposition sites.

Field Documentation of Unusual Post-Mortem Arthropod Activity on Human Remains

During a forensic investigation, the presence of physical marks on human remains can influence the interpretation of events related to the death of an individual. Some tissue injury on human remains can be misinterpreted as ante- or peri-mortem wounds by an investigator when in reality the markings resulted from post-mortem arthropod activity. Unusual entomological data were collected during a study examining the decomposition of a set of human remains in San Marcos, Texas. An adult female Pediodectes haldemani (Girard) (Orthoptera: Tettigoniidae) and an Armadillidium cf. vulgare (Isopoda: Armadilidiidae) were documented feeding on the remains. Both arthropods produced physical marks or artifacts on the remains that could be misinterpreted as attack, abuse, neglect, or torture. Additionally, red imported fire ants, Solenopsis invicta Buren (Hymenoptera: Formicidae), were observed constructing structures in the mark produced by the P. haldemani feeding. These observations provide insight into the potential of post-mortem arthropod damage to human remains, which previously had not been described for these taxa, and therefore, physical artifacts on any remains found in similar circumstances may result from arthropod activity and not ante- or peri-mortem wounds.

Microbial community functional change during vertebrate carrion decomposition

Microorganisms play a critical role in the decomposition of organic matter, which contributes to energy and nutrient transformation in every ecosystem. Yet, little is known about the functional activity of epinecrotic microbial communities associated with carrion. The objective of this study was to provide a description of the carrion associated microbial community functional activity using differential carbon source use throughout decomposition over seasons, between years and when microbial communities were isolated from eukaryotic colonizers (e.g., necrophagous insects). Additionally, microbial communities were identified at the phyletic level using high throughput sequencing during a single study. We hypothesized that carrion microbial community functional profiles would change over the duration of decomposition, and that this change would depend on season, year and presence of necrophagous insect colonization. Biolog EcoPlates™ were used to measure the variation in epinecrotic microbial community function by the differential use of 29 carbon sources throughout vertebrate carrion decomposition. Pyrosequencing was used to describe the bacterial community composition in one experiment to identify key phyla associated with community functional changes. Overall, microbial functional activity increased throughout decomposition in spring, summer and winter while it decreased in autumn. Additionally, microbial functional activity was higher in 2011 when necrophagous arthropod colonizer effects were tested. There were inconsistent trends in the microbial function of communities isolated from remains colonized by necrophagous insects between 2010 and 2011, suggesting a greater need for a mechanistic understanding of the process. These data indicate that functional analyses can be implemented in carrion studies and will be important in understanding the influence of microbial communities on an essential ecosystem process, carrion decomposition.

Destruction of single-species biofilms of Escherichia coli or Klebsiella pneumoniae subsp. pneumoniae by dextranase, lactoferrin, and lysozyme

The aim of this work was to determine the destructive activity of dextranase, lactoferrin, and lysozyme, against single species biofilms composed of either Klebsiella pneumoniae subsp. pneumoniae or Escherichia coli using the MBEC Assay. Luminescence measurements based on quantitation of the ATP present were used to determine the amount of biofilm elimination and correlated with quantity of live bacteria present in the sample. The data were analyzed employing a two-way ANOVA and Bonferroni post-test. Treatments resulted in percentage reductions of E. coli biofilms ranging from 73 to 98%. Lactoferrin (40 microg/ml) produced a significantly higher-percentage reduction than lysozyme (10 microg/ml) (P < 0.05), no other significant differences occurred. Similar treatments resulted in percentage reductions of K. pneumoniae subsp. pneumoniae biofilms ranging from 51 to 100%. Dextranase treatments produced a significantly lower percentage reduction than all other materials (P < 0.05), no other significant differences occurred. No material was capable of complete destruction of both single species biofilms; however, low concentrations of lactoferrin and lysozyme each removed 100% of the K. pneumoniae subsp. pneumoniae biofilm. Low concentrations of lactoferrin or lysozyme might be beneficial to prevent biofilm formation by K. pneumoniae subsp. pneumoniae.

The potential use of bacterial community succession in forensics as described by high throughput metagenomic sequencing

Decomposition studies of vertebrate remains primarily focus on data that can be seen with the naked eye, such as arthropod or vertebrate scavenger activity, with little regard for what might be occurring with the microorganism community. Here, we discuss the necrobiome, or community of organisms associated with the decomposition of remains, specifically, the "epinecrotic" bacterial community succession throughout decomposition of vertebrate carrion. Pyrosequencing was used to (1) detect and identify bacterial community abundance patterns that described discrete time points of the decomposition process and (2) identify bacterial taxa important for estimating physiological time, a time-temperature metric that is often commensurate with minimum post-mortem interval estimates, via thermal summation models. There were significant bacterial community structure differences in taxon richness and relative abundance patterns through the decomposition process at both phylum and family taxonomic classification levels. We found a significant negative linear relationship for overall phylum and family taxon richness as decomposition progressed. Additionally, we developed a statistical model using high throughput sequencing data of epinecrotic bacterial communities on vertebrate remains that explained 94.4 % of the time since placement of remains in the field, which was within 2-3 h of death. These bacteria taxa are potentially useful for estimating the minimum post-mortem interval. Lastly, we provide a new framework and standard operating procedure of how this novel approach of using high throughput metagenomic sequencing has remarkable potential as a new forensic tool. Documenting and identifying differences in bacterial communities is key to advancing knowledge of the carrion necrobiome and its applicability in forensic science.

A survey of bacterial diversity from successive life stages of black soldier fly (Diptera: Stratiomyidae) by using 16S rDNA pyrosequencing

Sustainable methods for managing waste associated with people and animals have been proposed in the past. Black soldier fly, Hermetia illucens (L.), larvae represent one of the more promising methods. Larvae reduce dry matter, bacteria, offensive odor, and house fly populations. Prepupae can be used as feedstuff for livestock. However, it is not known if such a method results in the proliferation of potential pathogens. Although some bacterial species have been cultured and identified from black soldier fly, a true appreciation of fly associated bacterial diversity is not known. Such information is needed to understand pathogen colonization on decomposing animal and plant waste in the presence of black soldier fly larvae as well as develop research strategies for maximizing the use of this fly to reduce waste without risking environmental harm. Using 454 sequencing, we surveyed bacterial diversity associated with successive life stages of the black soldier fly reared on plant material. Bacteria diversity classified (99.8%) across all life stages spanned six bacterial phyla with > or = 80% bootstrap support. Bacteroidetes and Proteobacteria were the most dominant phyla associated with the black soldier fly accounting for two-thirds of the fauna identified. Many of these bacteria would go undetected because of their inability to be cultured.

Disinfectant and antibiotic susceptibility profiles of Escherichia coli O157:H7 strains from cattle carcasses, feces, and hides and ground beef from the United States

The disinfectant and antibiotic susceptibility profiles of 344 Escherichia coli O157:H7 strains from cattle carcasses, feces, and hides and ground beef from the United States were determined. A low prevalence of antibiotic resistance was observed (14%). The highest prevalences of resistance were to sulfisoxazole (10.5%), tetracycline (9.9%), streptomycin (7%), and chloramphenicol (4.9%). Four strains were resistant to eight antibiotics (two strains from ground beef and one strain each from hide and preevisceration carcass swabs of cull cattle at harvest). Pulsed-field gel electrophoresis analysis of the E. coli O157:H7 strains revealed two major groups (designated 1 and 2) composed of 17 and 20 clusters, respectively. Clusters 1A, 1B, 1C, and 1G.1 were associated with multidrug-resistant strains. There was no observed correlation between disinfectant resistance and antibiotic resistance. Sixty-nine (20%) of the 344 strains were resistant to chlorhexidine or benzalkonium chloride or the MICs of benzyldimethyldodecylammonium chloride were elevated. Inducible resistance was observed at elevated concentrations of antibiotics (1.4%) and disinfectants (6.1%). The highest rate of disinfectant inducible resistance was to OdoBan, quaternary ammonium chlorides, and the surface disinfectants F25, FS512, and MG, which are used in dairies, restaurants, and food processing plants. High MICs (1,024 to 4,096 m g/ml) of acetic, lactic, and citric acids were found. The decreasing order of acid potency based on molar MICs (MICs(molar)) was acetic, citric, and lactic acid. The correlation of the concentration of dissociated organic acids and MICs(molar) strongly suggests that the observed inhibition of E. coli O157:H7 was primarily due to dissociated forms of the acids.

Evaluation of Salmonella movement through the gut of the lesser mealworm, Alphitobius diaperinus (Coleoptera: Tenebrionidae)

AIMS

The lesser mealworm, Alphitobius diaperinus is an important poultry pest prevalent during production that is capable of vectoring pathogens. This study was undertaken to determine the gut transit time of Salmonella for biosecurity risk analysis of pathogen dispersal into the environment.

METHODS

Adult and larval A. diaperinus were exposed to two concentrations of a fluorescently labeled Salmonella enterica for 15, 30, and 60 min time periods then externally disinfected to evaluate internal transfer of Salmonella. The insects were monitored every 30 min over 4 h and evacuated frass (feces) processed for the marker Salmonella. The minimum time monitored was 45 min (15 exposure+30 min time point), and the maximum was 5 h (60 exposure+4 h time point).

RESULTS

Adults treated with 10(6) or 10(8) colony-forming units (cfu)/mL, which produced Salmonella positive frass within the 5 h experimental time, displayed a mean gut transit time of 144.4 min (range 90-270 min) and 186.3 min (range 120-300 min), respectively. Larvae treated with 10(6) or 10(8) cfu/mL displayed a mean gut transit time of 172.5 min (range 120-300 min) and 131.7 min (range 60-300 min), respectively.

SIGNIFICANCE AND IMPACT OF STUDY

Understanding the sources and contribution of reservoir populations of pathogens in poultry production operations is important for development of biosecurity measures to mitigate their transfer. A. diaperinus are prevalent in production operations and difficult to suppress. Management standards accept the reutilization of litter in which insects survive between flock rotations. Removing litter and spreading it onto nearby fields results in the inadvertent dispersal of beetles. Few studies demonstrating the specific bacterial dispersal capacities of these insects have been performed. This study determined that Salmonella acquired internally, commonly transits the gut, allowed the insect to disperse viable pathogenic bacteria within 2-3 h.

Association between in vitro heterophil function and the feathering gene in commercial broiler chickens

We recently showed that in vitro heterophil functional efficiency in commercial broiler chickens is genetically controlled and may be a sex-associated trait. To further characterize the genetic mechanism(s) of heterophil functional efficiency, we wanted to determine whether the feathering gene, present on the Z sex chromosome, contributes to heterophil functional efficiency. Heterophils from two pairs of broiler lines were evaluated; each pair contained a fast feather (FF) (lines A and X) and a slow feather (SF) line (lines B and Y). On days 1 and 4 post-hatch, heterophils isolated from two sets of pure line broilers (A and B, and X and Y) were evaluated for their ability to (1) phagocytize Salmonella enteritidis, and (2) exhibit bactericidal activity against S. enteritidis. On days 1 and 4 post-hatch, heterophils isolated from the FF lines were statistically (P < or = 0.02) more proficient at phagocytizing S. enteritidis than heterophils from SF lines. Bactericidal activity was also statistically (p < or = 0.02) greater on day 1 post-hatch in the heterophils isolated from FF lines compared to heterophils isolated from SF lines. These data indicate that the presence of the FF gene locus on the Z sex chromosome contributes to heterophil function and may contribute to the early innate immune competence of a flock.

Conjugative transfer of plasmid-located antibiotic resistance genes within the gastrointestinal tract of lesser mealworm larvae, Alphitobius diaperinus (Coleoptera: Tenebrionidae)

The frequency of conjugative transfer of antimicrobial resistance plasmids between bacteria within the gastrointestinal tract of lesser mealworm larvae, a prevalent pest in poultry production facilities, was determined. Lesser mealworm larvae were exposed to a negative bacterial control, a donor Salmonella enterica serotype Newport strain, a recipient Escherichia coli, or both donor and recipient to examine horizontal gene transfer of plasmids. Horizontal gene transfer was validated post external disinfection, via a combination of selective culturing, testing of indole production by spot test, characterization of incompatibility plasmids by polymerase chain reaction, and profiling antibiotic susceptibility by a minimum inhibitory concentration (MIC) assay. Transconjugants were produced in all larvae exposed to both donor and recipient bacteria at frequencies comparable to control in vitro filter mating conjugation studies run concurrently. Transconjugants displayed resistance to seven antibiotics in our MIC panel and, when characterized for incompatibility plasmids, were positive for the N replicon and negative for the A/C replicon. The transconjugants did not display resistance to expanded-spectrum cephalosporins, which were associated with the A/C plasmid. This study demonstrates that lesser mealworm larvae, which infest poultry litter, are capable of supporting the horizontal transfer of antibiotic resistance genes and that this exchange can occur within their gastrointestinal tract and between different species of bacteria under laboratory conditions. This information is essential to science-based risk assessments of industrial antibiotic usage and its impact on animal and human health.

Planktonic and biofilm communities from 7-day-old chicken cecal microflora cultures: characterization and resistance to Salmonella colonization

Information implicating bacterial biofilms as contributory factors in the development of environmental bacterial resistance has been increasing. There is a lack of information regarding the role of biofilms within the microbial ecology of the gastrointestinal tract of food animals. This work used a continuous-flow chemostat model derived from the ceca of 7-day-old chicks to characterize these communities and their ability to neutralize invasion by Salmonella enterica serovar Typhimurium. We characterized and compared the biofilm and planktonic communities within these microcosms using automated ribotyping and the Analytical Profile Index biotyping system. Eleven species from eight different genera were identified from six culture systems. Klebsiella pneumoniae was isolated from all planktonic communities and four of the biofilm communities. Three of the communities resisted colonization by Salmonella enterica serovar Typhimurium, two communities suppressed growth, and one community succumbed to colonization. In cultures that resisted colonization, no Salmonella could be isolated from the biofilm; in cultures that succumbed to colonization, Salmonella was consistently found within the biofilms. This study was one of a series that provided a molecular-based characterization of both the biofilm and planktonic communities from continuous-flow culture systems derived from the cecal microflora of chicks, ranging in age from day-of-hatch to 14 days old. The one common factor relating to successful colonization of the culture was the presence of Salmonella within the biofilm. The capacity to sequester the introduced Salmonella into the biofilm appears to be a contributing factor to the inability of these cultures to withstand colonization by the Salmonella.

Characterization of planktonic and biofilm communities of day-of-hatch chicks cecal microflora and their resistance to Salmonella colonization

Recent concerns about the use of antimicrobials in food animals have increased interest in the microbial ecology and biofilms within their gastrointestinal tract. This work used a continuous-flow chemostat system to model the microbial community within the ceca from day-of-hatch chicks and its ability to resist colonization by Salmonella enterica serovar Typhimurium. We characterized the biofilm and planktonic communities from five cultures by using automated ribotyping. Eight species from six different genera were identified. Overall, the planktonic communities were more diverse, with 40% of the cultures containing four or more bacterial species. Eighty percent of the biofilm communities contained only one or two species of bacteria. Enterococcus faecalis was the only species isolated from all communities. None of the resulting microbial communities was able to resist colonization by S. enterica serovar Typhimurium. This is the first study to provide a molecular-based characterization of the biofilm and planktonic communities found in day-of-hatch chicken cecal microflora cultures.