Initial Characterization of the Pig Skin Bacteriome and Its Effect on In Vitro Models of Wound Healing

Variations in seminal microbiota and their functional implications in chickens adapted to high-altitude environments

Seminal fluid, once believed to be sterile, is now recognized as constituting a complex and dynamic environment inhabited by a diverse community of micro-organisms. However, research on the seminal microbiota in chickens is limited, and microbiota variations among different chicken breeds remain largely unexplored. In this study, we collected semen samples from Beijing You Chicken (BYC) and Tibetan Chicken (TC) and explored the characteristics of the microbiota using 16S rRNA gene sequencing. Additionally, we collected cloacal samples from the TC to control for environmental contamination. The results revealed that the microbial communities in the semen were significantly different from those in the cloaca. Firmicutes and Actinobacteriota were the predominant phyla in BYC and TC semen, respectively, with Lactobacillus and Phyllobacterium being the dominant genera in each group. Additionally, the seminal microbiota of BYC exhibited greater richness and evenness than that of TC. Principal coordinate analysis (PCoA) indicated significant intergroup differences between the seminal microbiotas of BYC and TC. Subsequently, by combining linear discriminant analysis effect size and random forest analyses, we identified Lactobacillus as the predominant microorganism in BYC semen, whereas Phyllobacterium dominated in TC semen. Furthermore, co-occurrence network analysis revealed a more intricate network in the BYC group than in the TC group. Additionally, unique microbial functional characteristics were observed in each breed, with TC exhibiting metabolic features potentially associated with their ability to adapt to high-altitude environments. The results of this study emphasized the unique microbiota present in chicken semen, which may be influenced by genetics and evolutionary history. Significant variations were observed between low-altitude and high-altitude breeds, highlighting the breed-specific implications of the seminal microbiota for reproduction and high-altitude adaptation.

Development and characterization of an automated behavioral assessment platform for the Göttingen minipig

The Göttingen minipig is fast becoming the standard for assessing dermal chemical hazards because, like most swine, its skin is predictive of human skin response and because this strain's smaller size makes laboratory manipulations and husbandry easier. Unfortunately, standard behavioral tests and apparatus have not been developed for behavioral assessments of this swine strain. Indeed, computer-controlled automated behavioral testing procedures are much needed. The present research advanced this goal by producing a home-cage behavioral testing system that could accommodate minipigs of various sizes (ages). An aluminum frame housed three levers for recording operant responses, and LEDs above and below each lever served as discriminative stimuli. A commercially available food pellet dispenser was attached to a specialized pellet receptacle capable of measuring pellet retrieval. Two behavioral tests were selected and adapted from our commonly used non-human primate behavioral assessments: delayed match-to-sample (a memory test) and temporal response differentiation (a time-estimation test). Minipigs were capable of learning both tests and attaining stable performance. Next, scopolamine was used to validate the sensitivity of the behavioral tests for gauging behavioral perturbations in this swine strain. Scopolamine dose-effect functions were comparable to those observed in other species, including non-human primates, wherein 37.5 µg/kg of scopolamine (administered intramuscularly) reduced responding approximately 50%. Thus, we were successful in developing the apparatus and automated operant behavioral tests necessary to characterize drug safety in this swine strain. This capability will be valuable for characterizing chemical agent toxicity as well as the safety and efficacy of medical countermeasures.

Identification of temporal shifts of oral bacteria in bone regeneration following mandibular bone defect injury and therapeutic surgery in a porcine model

BACKGROUND

Considered the second largest and most diverse microbiome after the gut, the human oral ecosystem is complex with diverse and niche-specific microorganisms. Although evidence is growing for the importance of oral microbiome in supporting a healthy immune system and preventing local and systemic infections, the influence of craniomaxillofacial (CMF) trauma and routine reconstructive surgical treatments on community structure and function of oral resident microbes remains unknown. CMF injuries affect a large number of people, needing extensive rehabilitation with lasting morbidity and loss of human productivity. Treatment efficacy can be complicated by the overgrowth of opportunistic commensals or multidrug-resistant pathogens in the oral ecosystem due to weakened host immune function and reduced colonization resistance in a dysbiotic oral microbiome.

AIMS

To understand the dynamics of microbiota's community structure during CMF injury and subsequent treatments, we induced supra-alveolar mandibular defect in Hanford miniature swine (n = 3) and compared therapeutic approaches of immediate mandibullar reconstructive (IMR) versus delayed mandibullar reconstructive (DMR) surgeries.

METHODS

Using bacterial 16S ribosomal RNA gene marker sequencing, the composition and abundance of the bacterial community of the uninjured maxilla (control) and the injured left mandibula (lingual and buccal) treated by DMR were surveyed up to 70-day post-wounding. For the injured right mandibula receiving IMR treatment, the microbial composition and abundance were surveyed up to 14-day post-wounding. Moreover, we measured sera level of biochemical markers (e.g., osteocalcin) associated with bone regeneration and healing. Computed tomography was used to measure and compare mandibular bone characteristics such as trabecular thickness between sites receiving DMR and IMR therapeutic approaches until day 140, the end of study period.

RESULTS

Independent of IMR versus DMR therapy, we observed similar dysbiosis and shifts of the mucosal bacteria residents after CMF injury and/or following treatment. There was an enrichment of Fusobacterium, Porphyromonadaceae, and Bacteroidales accompanied by a decline in Pasteurellaceae, Moraxella, and Neisseria relative abundance in days allotted for healing. We also observed a decline in species richness and abundance driven by reduction in temporal instability and inter-animal heterogeneity on days 0 and 56, with day 0 corresponding to injury in DMR group and day 56 corresponding to delayed treatment for DMR or injury and immediate treatment for the IMR group. Analysis of bone healing features showed comparable bone-healing profiles for IMR vs. DMR therapeutic approach.

High-frequency electric knife smoke particles: An experimental study on factors influencing emission characteristics

During surgery, the use of a high-frequency electric knife produces smoke, which can be harmful to the health of indoor medical staff and patients. The quantity and particle size distribution of smoke particles produced by different tissues may vary. Understanding the release characteristics of these smoke particles is necessary to clarify their impact on the surgical environment and to seek effective smoke control methods. A previous comparative analysis of human and pig tissues revealed that they share similar water and fat compositions in certain anatomical regions. In this study, we investigated the emission characteristics of smoke particles from various tissues of pigs (skeletal muscle, liver, kidney, skin, and subcutaneous fat) under different operating powers of an electric knife. We measured the indoor particle number concentration (particle concentration), and estimated the PM2.5 mass concentration (PM2.5 concentration), particle size distribution, and emission rate of the smoke particles. The study obtained the particle emission rates of different tissues under different electric knife operating powers, results of which showed that (1) during the operation of the electric knife, mainly small particles below 1 μm are produced. Among them, particles of 0.3 μm were the most abundant, with a particle concentration level of up to 109 particles/m3, accounting for 85.17-97.64% of the total particle number, and as the particle size increased, the particle concentration and percentage decreased significantly. (2) The water and fat compositions of different tissues influenced the indoor particle concentration and emission rate of the smoke emitted by the electric knife. Among different tissues, subcutaneous fat tissue had the lowest particle concentration and emission rate. (3) The electric knife operating power mainly affected particles below 1 μm, and except for kidney tissue, the indoor concentration and emission rate of these particle sizes were positively correlated with the power. The experimental results can provide data reference for the use of high-frequency electric knives in surgeries involving different human tissues in the operating room.

Meta-Analysis of Publicly Available Clinical and Preclinical Microbiome Data From Studies of Burn Injury

Following burn injury, alterations in host commensal microbiota across body spaces may leave patients susceptible to opportunistic pathogens and serious sequelae such as sepsis. Generally, studies examining the microbiome postburn have had a limited sample size and lack of longitudinal data, which coupled with experimental and analytic variation, impacts overall interpretation. We performed a meta-analysis of publicly available sequencing data from preclinical and clinical burn studies to determine if there were consistent alterations in the microbiome across various anatomical sites and hosts. Ten human and animal 16S rRNA sequencing studies spanning respiratory, urinary, cutaneous, and gastrointestinal microbiomes were included. Taxonomic classification and alpha and beta diversity metrics were analyzed using QIIME2 v2021.8. Alpha diversity was consistently higher in control samples compared to burn-injured samples which were also different based on host and anatomical location; however, phylogenetic evaluation (ie, Faith PD) elucidated more significant differences compared to taxonomic metrics (ie, Shannon entropy). Beta diversity analysis based on weighted UniFrac showed that rodent specimens clustered less closely to humans than pig samples for both rectal and skin sources. Host species and performing institute were found to have a significant impact on community structure. In rectal samples, bacterial composition in pig and human burn samples included Bacteroidetes, Firmicutes, and Proteobacteria, while rodent samples were dominated by Firmicutes. Proteobacteria and Firmicutes increased on burned skin in each host species. Our results suggest that host species and the performing institute strongly influence microbiome structure. Burn-induced alterations in microbiome diversity and taxa exist across hosts, with phylogenetic metrics more valuable than others. Coordinated, multicenter studies, both clinical and preclinical, within the burn community are needed to more completely realize the diagnostic and therapeutic potential of the microbiome for improving outcomes postburn.

Harnessing diversity and antagonism within the pig skin microbiota to identify novel mediators of colonization resistance to methicillin-resistant Staphylococcus aureus

The microbiota mediate multiple aspects of skin barrier function, including colonization resistance to pathogens such as Staphylococcus aureus. The endogenous skin microbiota limits S. aureus colonization via competition and direct inhibition. Novel mechanisms of colonization resistance are promising therapeutic targets for drug-resistant infections, such as those caused by methicillin-resistant S. aureus (MRSA). Here, we developed and characterized a swine model of topical microbiome perturbation and MRSA colonization. As in other model systems, topical antimicrobial treatment had a little discernable effect on community diversity though the overall microbial load was sensitive to multiple types of intervention, including swabbing. In parallel, we established a porcine skin culture collection and screened 7,700 isolates for MRSA inhibition. Using genomic and phenotypic criteria, we curated three isolates to investigate whether prophylactic colonization would inhibit MRSA colonization in vivo. The three-member consortium together, but not individually, provided protection against MRSA colonization, suggesting cooperation and/or synergy among the strains. Inhibitory isolates were represented across all major phyla of the pig skin microbiota and did not have a strong preference for inhibiting closely related species, suggesting that relatedness is not a condition of antagonism. These findings reveal the porcine skin as an underexplored reservoir of skin commensal species with the potential to prevent MRSA colonization and infection. IMPORTANCE The skin microbiota is protective against pathogens or opportunists such as S. aureus, the most common cause of skin and soft tissue infections. S. aureus can colonize normal skin and nasal passages, and colonization is a risk factor for infection, especially on breach of the skin barrier. Here, we established a pig model to study the competitive mechanisms of the skin microbiota and their role in preventing colonization by MRSA. This drug-resistant strain is also a livestock pathogen, and swine herds can be reservoirs of MRSA carriage. From 7,700 cultured skin isolates, we identified 37 unique species across three phyla that inhibited MRSA. A synthetic community of three inhibitory isolates provided protection together, but not individually, in vivo in a murine model of MRSA colonization. These findings suggest that antagonism is widespread in the pig skin microbiota, and these competitive interactions may be exploited to prevent MRSA colonization.

A pig model of tunneled dialysis catheter (TDC) infection and dysfunction: Opportunities for therapeutic innovation

BACKGROUND

Although tunneled dialysis catheters (TDC) are far from ideal, they still represent the main form of vascular access for most patients beginning dialysis. Catheters are easy to place and allow patients instant access to dialysis, but regardless of these benefits, catheters are associated with a high incidence of significant complications like bloodstream infections, central venous stenosis, thrombosis, and dysfunction. In the present study, we aim to describe and characterize a swine model of catheter dysfunction and bloodstream infection, that recreates the clinical scenario, to help to serve as a platform to develop therapeutic innovations for this important clinical problem.

METHODS

Six Yorkshire cross pigs were used in this study. Non-coated commercial catheters were implanted in the external jugular recreating the main features of common clinical practice. Catheters were aseptically accessed twice a week for a mock dialysis procedure (flushing in and out) to assess for and identify catheter dysfunction. Animals were monitored daily for infections; once detected, blood samples were collected for bacterial culture and antibiograms. Study animals were euthanized when nonresponsive to treatment. Tissue samples were collected in a standardized fashion for macroscopic inspection and histological analysis.

RESULTS

The data analysis revealed an early onset of infection with a median time to infection of 9 days, 40% of the isolates were polymicrobial, and the average time to euthanasia was 20.16 ± 7.3 days. Median time to catheter dysfunction onset was 6 days post-implantation. Postmortem dissection revealed external fibrin sheath and internal thrombosis as the main causes of catheter dysfunction. There was also evidence of central venous stenosis with positive cells for αSMA, CD68, Ki67, Smoothelin, and Vimentin within the venous neointima.

CONCLUSIONS

The described model represents a reliable and reproducible large animal model of catheter dysfunction and bloodstream infection, which recreates all the main complications of TDC's and so could be used as a validated large animal model to develop new therapies for TDC related infection, thrombosis/dysfunction and central venous stenosis.

Characterization of pig skin microbiome and appraisal as an in vivo subcutaneous injection model

Pig skin is commonly used in the medical industry as an injection model due to its compelling physiological affinity to human skin. However, the pig neck skin microflora remains largely uncharacterized, which may have undesirable implications for the translatability of results to humans. This study aimed to characterize pig neck skin microbiome with direct comparison with human skin microflora at emblematic injection sites to appraise its suitability as an injection model. Ten minipigs were sampled with tape strips and swabs and analysed by matrix-assisted laser desorption/ionization-time of flight mass spectrometry and 16S/ITS high throughput sequencing and confocal laser scanning microscopy. Results were directly compared with previous investigations of human injection sites. Pig skin was dominated by phyla 94.8% Firmicutes, 3% Proteobacteria, and 2.2% Actinobacteria. Staphylococcus spp. prevailed (44.4%) at the genus level with S. capitis and S. chromogenes present in all samples. Pig skin revealed populations in the 104 colony-forming units (CFU)/cm2 range with 3% identified as Gram-negative and increased alpha diversity (compared with 102 CFU/cm2 and 10% in humans). While notable taxonomical differences on species levels were seen, pig skin encompassed 97.1% of genera found in human samples. The increased population and variation found support the pig neck as an imperfect but fidelitous subcutaneous injection model that can adequately challenge devices from a microbial standpoint.

Using engineered water nanostructures (EWNS) for wound disinfection: Case study of Acinetobacter baumannii inactivation on skin and the inhibition of biofilm formation

Engineered water nanostructures (EWNS) were utilized to deliver a cocktail of nature derived antimicrobials, to assess their efficacy as a solution to the problem of wound infections. The wound related microorganism Acinetobacter baumannii was inoculated on stainless steel and porcine skin and treated with EWNS. EWNS were able to reduce A. baumannii on stainless steel by 4.79 logs in 15 min, and 2 logs in 30 min on porcine skin. The EWNS were able to reduce the strength of A. baumannii biofilm on stainless steel by 87.31% as measured with the XTT assay (P < .001) and 86.27% in cellular counts (P < .001), after two EWNS interventions of 30 min each. Total antimicrobial dose delivered to the surface was 1.42 ng. SEM of biofilms after EWNS treatment showed reduced biomass. These results indicate that the EWNS technology has potential for application in field of wound disinfection and healing.

Characterization of the Skin Bacteriome and Histology Changes in Diabetic Pigs

Chronic wound is one of the most common complications that are associated with diabetes. The cutaneous microbiome is known to play essential roles in the regulation of barrier function and protecting against potential assault. Thus, it is necessary to gain a better understanding of the relationship between microbial community and skin structures in unwounded diabetic skin to explore possible preventive strategies. To achieve the same, a pig diabetic model was built in the present study. Further,16S rDNA sequencing was used to characterize the skin bacteriome. It was observed that the pigs showed skin bacteriome similar to humans in the non-diabetes group, while it varied in the case of diabetes. Further, the β-diversity analysis showed that the bacterial community was significantly different under the diabetes group. More species differences were identified between the two groups at genus level. The predictive function analysis also showed the involvement of significantly different pathways of microbial gene function in diabetes. In agreement with this, skin histology analysis also showed signs of reduced epidermal thickness and rete ridges in diabetic skin. Less proliferation of keratinocytes and impaired TJ barrier was also detected. This evidence suggested that pigs might serve as the best surrogate for cutaneous microbiome studies. Altogether, the present study reported that the skin bacteriome and histology changed significantly in unwounded diabetic skin, which provided a theoretical basis for the regulation of disordered skin bacteriome. The findings of the study would assist in the improvement of the skin environment and prevention of skin infection and chronic wounds.

Dysbiosis of skin microbiome and gut microbiome in melanoma progression

Background

The microbiome alterations are associated with cancer growth and may influence the immune system and response to therapy. Particularly, the gut microbiome has been recently shown to modulate response to melanoma immunotherapy. However, the role of the skin microbiome has not been well explored in the skin tumour microenvironment and the link between the gut microbiome and skin microbiome has not been investigated in melanoma progression. Therefore, the aim of the present study was to examine associations between dysbiosis in the skin and gut microbiome and the melanoma growth using MeLiM porcine model of melanoma progression and spontaneous regression.

Results

Parallel analysis of cutaneous microbiota and faecal microbiota of the same individuals was performed in 8 to 12 weeks old MeLiM piglets. The bacterial composition of samples was analysed by high throughput sequencing of the V4-V5 region of the 16S rRNA gene. A significant difference in microbiome diversity and richness between melanoma tissue and healthy skin and between the faecal microbiome of MeLiM piglets and control piglets were observed. Both Principal Coordinate Analysis and Non-metric multidimensional scaling revealed dissimilarities between different bacterial communities. Linear discriminant analysis effect size at the genus level determined different potential biomarkers in multiple bacterial communities. Lactobacillus, Clostridium sensu stricto 1 and Corynebacterium 1 were the most discriminately higher genera in the healthy skin microbiome, while Fusobacterium, Trueperella, Staphylococcus, Streptococcus and Bacteroides were discriminately abundant in melanoma tissue microbiome. Bacteroides, Fusobacterium and Escherichia-Shigella were associated with the faecal microbiota of MeLiM piglets. Potential functional pathways analysis based on the KEGG database indicated significant differences in the predicted profile metabolisms between the healthy skin microbiome and melanoma tissue microbiome. The faecal microbiome of MeLiM piglets was enriched by genes related to membrane transports pathways allowing for the increase of intestinal permeability and alteration of the intestinal mucosal barrier.

Conclusion

The associations between melanoma progression and dysbiosis in the skin microbiome as well as dysbiosis in the gut microbiome were identified. Results provide promising information for further studies on the local skin and gut microbiome involvement in melanoma progression and may support the development of new therapeutic approaches.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-022-02458-5.

Importance of the pig as a human biomedical model

[Figure: see text].

Analysis of Porcine Model of Fecal-Induced Peritonitis Reveals the Tropism of Blood Microbiome

Recent studies have suggested the existence of a blood microbiome in the healthy host. However, changes in the blood microbiome upon bloodstream infection are not known. Here, we analyzed the dynamics of the blood microbiome in a porcine model of polymicrobial bacteremia induced by fecal peritonitis. Surprisingly, we detected bacterial populations in the bloodstream even before the infection, and these populations were maintained over time. The native blood microbiome was notably taxonomically different from the fecal microbiome that was used to induce peritonitis, reflecting microbial tropism for the blood. Although the population composition after the infection was similar to that of the native blood microbiome, new bacterial strains entered the bloodstream upon peritonitis induction as clinical symptoms relevant to sepsis developed. This indicates that the bacteria detected in the blood before peritonitis induction were derived from the blood rather than a contamination. Comparison of the functional pathways enriched in the blood and fecal microbiomes revealed that communication and stress management pathways are essential for the survival of the blood microbiome.

The Effect of Burn Resuscitation Volumes on the Gut Microbiome in a Swine Model

INTRODUCTION

While recent reports underscore the significance of the gut microbiome (GM) in health and disease, its importance in burn outcomes remains unclear. Moreover, aggressive intravenous (IV) fluid resuscitation of patients may alter intestinal flora. Herein, we describe GM changes following a large burn in swine randomized to different volumes of IV Lactated Ringers' (LR).

METHODS

Anesthetized Yorkshire swine sustained 40% total body surface area full-thickness burns and were randomized to different volumes of IV LR: none (n = 5), 15 mL/kg/d (low; n = 6), or 80 mL/kg/d (high; n = 6). At baseline and days 1 and 2, fecal swabs were collected for 16s rDNA sequencing. Proximal jejunum was collected immediately after euthanasia (day 2) for western blot, histopathology, and cytokine analyses.

RESULTS

Burns produced significant shifts in β-diversity and non-significant reductions in α-diversity that did not recover regardless of treatment group. Burn-induced increases in Proteobacteria and decreases in Firmicutes were attenuated by IV fluids in a dose-dependent manner, and also correlated with α-diversity. IV fluids caused a dose-dependent increase in Bacteroides and prevented a transient increase in the opportunistic pathogen Haemophilus parainfluenzae. While high volumes of IV fluids increased intestinal Hsp70 levels (P = 0.0464), they reduced SGLT1 (P = 0.0213) and caspase3 (P = 0.0139) levels. IV fluids elicited a non-specific cytokine response; however, Bacteroidetes levels correlated with intestinal IL18 levels (P = 0.0166, R = 0.4201).

CONCLUSIONS

We present the first report on the gut microbiome in a porcine burn model, and present data to suggest that IV fluids may influence GM and gut functional proteins following a burn. Overall, burn-induced GM diversity shifts may expose diagnostic and/or therapeutic targets to improve outcomes.

Characterising Post-mortem Bacterial Translocation Under Clinical Conditions Using 16S rRNA Gene Sequencing in Two Animal Models

Sudden unexpected death in infancy (SUDI) is the sudden and unexpected death of an apparently healthy infant occurring within the first year of life where the cause is not immediately obvious. It is believed that a proportion of unexplained infant deaths are due to an infection that remains undiagnosed. The interpretation of post-mortem microbiology results is difficult due to the potential false-positives, a source of which is post-mortem bacterial translocation. Post-mortem bacterial translocation is the spread of viable bacteria from highly colonised sites to extra-intestinal tissues. We hypothesise that although post-mortem bacterial translocation occurs, when carcasses are kept under controlled routine clinical conditions it is not extensive and can be defined using 16S rRNA gene sequencing. With this knowledge, implementation of the 16S rRNA gene sequencing technique into routine clinical diagnostics would allow a more reliable retrospective diagnosis of ante-mortem infection. Therefore, the aim of this study was to establish the extent of post-mortem bacterial translocation in two animal models to establish a baseline sequencing signal for the post-mortem process. To do this we used 16S rRNA gene sequencing in two animal models over a 2 week period to investigate (1) the bacterial community succession in regions of high bacterial colonisation, and (2) the bacterial presence in visceral tissues routinely sampled during autopsy for microbiological investigation. We found no evidence for significant and consistent post-mortem bacterial translocation in the mouse model. Although bacteria were detected in tissues in the piglet model, we did not find significant and consistent evidence for post-mortem bacterial translocation from the gastrointestinal tract or nasal cavity. These data do not support the concept of significant post-mortem translocation as part of the normal post-mortem process.

PCL/Andiroba Oil (Carapa guianensis Aubl.) Hybrid Film for Wound Healing Applications

Developing a biomimetic material to wound care is an emerging need for the healing process. Poly (ε-caprolactone) (PCL) is a polymer with the necessary dressing's requirements often used in medicine. Their surface, physic-chemical and biological properties can be modified by adding bioactive compounds, such as andiroba seed oil (Carapa guianensis). This Amazonian natural plant has medicinal and pharmacological properties. For this purpose, PCL polymeric films incorporated with andiroba oil were investigated. The synthesis of hybrids materials was carried out in the solvent casting method. Thermal properties were evaluated using thermogravimetric analysis (TGA/DTGA) and differential scanning calorimetry (DSC). The solvent type on the surface and hydrophilicity of samples was studied using a scanning electron microscope (SEM). Additionally, contact angle measurements, functional groups analysis, fluid absorption capacity, and cell viability were performed. The results demonstrated the influences of andiroba oil under the morphology and thermal properties of the polymeric matrix; the hydrophilicity of the hybrid film obtained by acetic acid was reduced by 13%; the porosity decreased as the concentration of oil increased, but its higher thermal stability. The L929 cell line's proliferation was observed in all materials, and it presented nontoxic nature. It was demonstrated the ability of PCL hybrid film as a matrix for cell growth. Then, the materials were proved potential candidates for biomedical applications.

Polyphosphazenes enable durable, hemocompatible, highly efficient antibacterial coatings

Biocompatible antibacterial coatings are highly desirable to prevent bacterial colonization on a wide range of medical devices from hip implants to skin grafts. Traditional polyelectrolytes are unable to directly form coatings with cationic antibiotics at neutral pH and suffer from high degrees of antibiotic release upon exposure to physiological concentrations of salt. Here, novel inorganic-organic hybrid polymer coatings based on direct layer-by-layer assembly of anionic polyphosphazenes (PPzs) of various degrees of fluorination with cationic antibiotics (polymyxin B, colistin, gentamicin, and neomycin) are reported. The coatings displayed low levels of antibiotic release upon exposure to salt and pH-triggered response of controlled doses of antibiotics. Importantly, coatings remained highly surface active against Escherichia coli and Staphylococcus aureus, even after 30 days of pre-exposure to physiological conditions (bacteria-free) or after repeated bacterial challenge. Moreover, coatings displayed low (<1%) hemolytic activity for both rabbit and porcine blood. Coatings deposited on either hard (Si wafers) or soft (electrospun fiber matrices) materials were non-toxic towards fibroblasts (NIH/3T3) and displayed controllable fibroblast adhesion via PPz fluorination degree. Finally, coatings showed excellent antibacterial activity in ex vivo pig skin studies. Taken together, these results suggest a new avenue to form highly tunable, biocompatible polymer coatings for medical device surfaces.

RNA delivery by extracellular vesicles in mammalian cells and its applications

The term 'extracellular vesicles' refers to a heterogeneous population of vesicular bodies of cellular origin that derive either from the endosomal compartment (exosomes) or as a result of shedding from the plasma membrane (microvesicles, oncosomes and apoptotic bodies). Extracellular vesicles carry a variety of cargo, including RNAs, proteins, lipids and DNA, which can be taken up by other cells, both in the direct vicinity of the source cell and at distant sites in the body via biofluids, and elicit a variety of phenotypic responses. Owing to their unique biology and roles in cell-cell communication, extracellular vesicles have attracted strong interest, which is further enhanced by their potential clinical utility. Because extracellular vesicles derive their cargo from the contents of the cells that produce them, they are attractive sources of biomarkers for a variety of diseases. Furthermore, studies demonstrating phenotypic effects of specific extracellular vesicle-associated cargo on target cells have stoked interest in extracellular vesicles as therapeutic vehicles. There is particularly strong evidence that the RNA cargo of extracellular vesicles can alter recipient cell gene expression and function. During the past decade, extracellular vesicles and their RNA cargo have become better defined, but many aspects of extracellular vesicle biology remain to be elucidated. These include selective cargo loading resulting in substantial differences between the composition of extracellular vesicles and source cells; heterogeneity in extracellular vesicle size and composition; and undefined mechanisms for the uptake of extracellular vesicles into recipient cells and the fates of their cargo. Further progress in unravelling the basic mechanisms of extracellular vesicle biogenesis, transport, and cargo delivery and function is needed for successful clinical implementation. This Review focuses on the current state of knowledge pertaining to packaging, transport and function of RNAs in extracellular vesicles and outlines the progress made thus far towards their clinical applications.

Human-microorganism mutualism theory: Possible mechanisms for the delayed chronic wound healing process

Skin microbial flora was believed to can implicate skin health, and many recent reports point out a close linkage between the dysbiosis of the microbiome with the disease. Changes of microbiota, including diversity, species, and abundance, have been demonstrated in disease states, and it was believed the changes may cause infection and chronicity of the debilitating wounds. And it was been found a reverse of the dysbiosis after the effective treatment, but it failed to find a positive effect of antibiotic therapy on skin disease without significant clinical infection. The microbiomes were compared to the 'second gene reservoir', and indicated that their co-existing with the human being is a result of co-evolution. The current studies have shown that the microbial community on the skin surface should have an ideal optimal state, which can effectively regulate the immune tolerance and help to avoid the invasion of external pathogenic bacteria, then the body can be in a relatively healthy state. In this paper, we hypothesized that failing to maintain the harmonious relationship between microbes and human beings is the reason we suffering from most skin diseases, including chronic non-healing wounds. Thus, the dysbiosis of skin microbiota theory can help us better understand the mechanism of wound formation and problems encountered in wound treatment.

Wound protectors for improved exposure in open hernia repair

INTRODUCTION

Achieving adequate surgical exposure is fundamental to good surgical practice. Traditionally, in the repair of ventral and open inguinal hernias, this has been accomplished with the aid of self-retaining retractors or by extending the incision length. We propose that using disposable wound protectors, surgical exposure will be improved for a given incision length in the repair of ventral and open inguinal hernias, compared to traditional methods.

METHOD

Through the use of an animal tissue model, we compared incisions of varying lengths and measured the dimensions of the exposure achieved with disposable wound protectors (Alexis™) and a Mollison self-retainer. We calculated the surface area and, therefore, exposure gained using the specified wound retraction devices and compared the results.

RESULTS

The average superficial surface area of wound with a self-retainer compared to the small and extra-small disposable wound protector was 2.65 cm² vs 2.27 cm² (small) and 2.2 cm² (extra-small) for 2 cm incision length, 3.6 cm² vs 4.93 cm² and 4.2 cm² for 3 cm incision length, 5.19 cm² vs 8.25 cm² and 6.27 cm² for 4 cm incision length, 6.17 cm² vs 12.25 cm² and 9.07 cm² for 5 cm incision length, and 8.75 cm² vs 16.73 cm² and 10.78 cm² for 6 cm incision length [p = 0.038 (small) and p = 0.049 (extra-small)]. Our results show a statistically significant increase in surface area of a wound for each incision length when a disposable wound protector was used for exposure, compared to a self-retainer.

CONCLUSION

Our results demonstrate that the use of disposable wound protectors provides superior surgical exposure for a given incision length compared to traditional techniques in the repair of ventral and open inguinal hernia repairs.

Microbiome Imbalances: An Overlooked Potential Mechanism in Chronic Nonhealing Wounds

Chronic nonhealing wounds are a severe burden to health care systems worldwide, causing millions of patients to have lengthy hospital stays, high health care costs, periods of unemployment, and reduced quality of life. Moreover, treating chronic nonhealing wounds effectively and reasonably in countries with limited medical resources can be extremely challenging. With many outstanding questions surrounding chronic nonhealing wounds, in this review, we offer changes to the microbiome as a potentially ignored mechanism important in the formation and treatment of chronic wounds. Our analysis helps bring a whole new understanding to wound formation and healing and provides a potential breakthrough in the treatment of chronic nonhealing wounds in the future.

Multi-Method Characterization of the Human Circulating Microbiome

The term microbiome describes the genetic material encoding the various microbial populations that inhabit our body. Whilst colonization of various body niches (e.g., the gut) by dynamic communities of microorganisms is now universally accepted, the existence of microbial populations in other "classically sterile" locations, including the blood, is a relatively new concept. The presence of bacteria-specific DNA in the blood has been reported in the literature for some time, yet the true origin of this is still the subject of much deliberation. The aim of this study was to investigate the phenomenon of a "blood microbiome" by providing a comprehensive description of bacterially derived nucleic acids using a range of complementary molecular and classical microbiological techniques. For this purpose we utilized a set of plasma samples from healthy subjects (n = 5) and asthmatic subjects (n = 5). DNA-level analyses involved the amplification and sequencing of the 16S rRNA gene. RNA-level analyses were based upon the de novo assembly of unmapped mRNA reads and subsequent taxonomic identification. Molecular studies were complemented by viability data from classical aerobic and anaerobic microbial culture experiments. At the phylum level, the blood microbiome was predominated by Proteobacteria, Actinobacteria, Firmicutes, and Bacteroidetes. The key phyla detected were consistent irrespective of molecular method (DNA vs. RNA), and consistent with the results of other published studies. In silico comparison of our data with that of the Human Microbiome Project revealed that members of the blood microbiome were most likely to have originated from the oral or skin communities. To our surprise, aerobic and anaerobic cultures were positive in eight of out the ten donor samples investigated, and we reflect upon their source. Our data provide further evidence of a core blood microbiome, and provide insight into the potential source of the bacterial DNA/RNA detected in the blood. Further, data reveal the importance of robust experimental procedures, and identify areas for future consideration.

Melanoma-related changes in skin microbiome

Melanoma is the least common form of skin tumor, but it is potentially the most dangerous and responsible for the majority of skin cancer deaths. We suggest that the skin microbiome might be changed during the progression of melanoma. The aim of this study is to compare the composition of the skin microbiota between different locations (skin and melanoma) of a MeLiM (Melanoma-bearing Libechov Minipig) pig model (exophytic melanoma). Ninety samples were used for PCR-DGGE analysis with primers specifically targeting the V3 region of the 16S rRNA gene. The profiles were used for cluster analysis by UPGMA and principal coordinate analysis PCoA and also to calculate the diversity index (Simpson index of diversity). By comparing the obtained results, we found that both bacterial composition and diversity were significantly different between the skin and melanoma microbiomes. The abundances of Fusobacterium and Trueperella genera were significantly increased in melanoma samples, suggesting a strong relationship between melanoma development and skin microbiome changes.

Extracellular polymeric substance (EPS)-degrading enzymes reduce staphylococcal surface attachment and biocide resistance on pig skin in vivo

Staphylococcal extracellular polymeric substances (EPS) such as extracellular DNA (eDNA) and poly-N-acetylglucosamine surface polysaccharide (PNAG) mediate numerous virulence traits including host colonization and antimicrobial resistance. Previous studies showed that EPS-degrading enzymes increase staphylococcal biocide susceptibility in vitro and in vivo, and decrease virulence in animal models. In the present study we tested the effect of EPS-degrading enzymes on staphylococcal skin colonization and povidone iodine susceptibility using a novel in vivo pig model that enabled us to colonize and treat 96 isolated areas of skin on a single animal in vivo. To quantitate skin colonization, punch biopsies of colonized areas were homogenized, diluted, and plated on agar for colony forming unit enumeration. Skin was colonized with either Staphylococcus epidermidis or Staphylococcus aureus. Two EPS-degrading enzymes, DNase I and the PNAG-degrading enzyme dispersin B, were employed. Enzymes were tested for their ability to inhibit skin colonization and detach preattached bacteria. The effect of enzymes on the susceptibility of preattached S. aureus to killing by povidone iodine was also measured. We found that dispersin B significantly inhibited skin colonization by S. epidermidis and detached preattached S. epidermidis cells from skin. A cocktail of dispersin B and DNase I detached preattached S. aureus cells from skin and increased their susceptibility to killing by povidone iodine. These findings suggest that staphylococcal EPS components such as eDNA and PNAG contribute to skin colonization and biocide resistance in vivo. EPS-degrading enzymes may be a useful adjunct to conventional skin antisepsis procedures in order to further reduce skin bioburden.

The Cutaneous Microbiome and Wounds: New Molecular Targets to Promote Wound Healing

The ecological community of microorganisms in/on humans, termed the microbiome, is vital for sustaining homeostasis. While culture-independent techniques have revealed the role of the gut microbiome in human health and disease, the role of the cutaneous microbiome in wound healing is less defined. Skin commensals are essential in the maintenance of the epithelial barrier function, regulation of the host immune system, and protection from invading pathogenic microorganisms. In this review, we summarize the literature derived from pre-clinical and clinical studies on how changes in the microbiome of various acute and chronic skin wounds impact wound healing tissue regeneration. Furthermore, we review the mechanistic insights garnered from model wound healing systems. Finally, in the face of growing concern about antibiotic-resistance, we will discuss alternative strategies for the treatment of infected wounds to improve wound healing and outcomes. Taken together, it has become apparent that commensals, symbionts, and pathogens on human skin have an intimate role in the inflammatory response that highlights several potential strategies to treat infected, non-healing wounds. Despite these promising results, there are some contradictory and controversial findings from existing studies and more research is needed to define the role of the human skin microbiome in acute and chronic wound healing.

A detailed investigation of the porcine skin and nose microbiome using universal and Staphylococcus specific primers

MRSA is an increasing problem in humans as well as livestock. The bacterial co-colonization of the skin in MRSA carriers has been poorly investigated and moreover, there have been no methods for high resolution investigations of the Staphylococcus genus apart from tediously culturing or doing multiple PCRs. On 120 samples from pig ear, skin and nose, we generated amplicons from the V1-V2 region of the 16S rRNA gene to gather an overview of the genus-level microbiome, along with using MRSA specific plates to count MRSA. In parallel with this, amplicons of the tuf gene were generated, targeting only a region of the tuf gene found only in the Staphylococcus genus. Using these methods, we determined a core microbiota across the healthy pig and determined the Staphylococcus genus to be dominated by S. equorum. Moreover, we found Streptococcus to be inversely associated with Staphylococcus and MRSA, suggesting a role for this genus in combating MRSA. In this work, we have thoroughly investigated the skin and nose microbiome of the pig and developed a high throughput method for profiling the Staphylococcus genus which we believe will be useful for further investigations.

Drug delivery and tissue engineering to promote wound healing in the immunocompromised host: Current challenges and future directions

As regenerative medicine matures as a field, more promising technologies are being translated from the benchtop to the clinic. However, many of these strategies are designed with otherwise healthy hosts in mind and validated in animal models without other co-morbidities. In reality, many of the patient populations benefiting from drug delivery and tissue engineering-based devices to enhance wound healing also have significant underlying immunodeficiency. Specifically, patients suffering from diabetes, malignancy, human immunodeficiency virus, post-organ transplantation, and other compromised states have significant pleotropic immune defects that affect wound healing. In this work, we review the role of different immune cells in the regenerative process, highlight the effect of several common immunocompromised states on wound healing, and discuss different drug delivery strategies for overcoming immunodeficiencies.

Exploring the microbiome of healthy and diseased peri-implant sites using Illumina sequencing

AIM

To compare the microbiome of healthy (H) and diseased (P) peri-implant sites and determine the core peri-implant microbiome.

MATERIALS AND METHODS

Submucosal biofilms from 32 H and 35 P sites were analysed using 16S rRNA sequencing (MiSeq, Illumina), QIIME and HOMINGS. Differences between groups were determined using principal coordinate analysis (PCoA), t tests and Wilcoxon rank sum test and FDR-adjusted. The peri-implant core microbiome was determined.

RESULTS

PCoA showed partitioning between H and P at all taxonomic levels. Bacteroidetes, Spirochetes and Synergistetes were higher in P, while Actinobacteria prevailed in H (p < .05). Porphyromonas and Treponema were more abundant in P while Rothia and Neisseria were higher in H (p < .05). The core peri-implant microbiome contained Fusobacterium, Parvimonas and Campylobacter sp. T. denticola, and P. gingivalis levels were higher in P, as well as F. alocis, F. fastidiosum and T. maltophilum (p < .05).

CONCLUSION

The peri-implantitis microbiome is commensal-depleted and pathogen-enriched, harbouring traditional and new pathogens. The core peri-implant microbiome harbours taxa from genera often associated with periodontal inflammation.

Captive bottlenose dolphins and killer whales harbor a species-specific skin microbiota that varies among individuals

Marine animals surfaces host diverse microbial communities, which play major roles for host’s health. Most inventories of marine animal surface microbiota have focused on corals and fishes, while cetaceans remain overlooked. The few studies focused on wild cetaceans, making difficult to distinguish intrinsic inter- and/or intraspecific variability in skin microbiota from environmental effects. We used high-throughput sequencing to assess the skin microbiota from 4 body zones of 8 bottlenose dolphins (Tursiops truncatus) and killer whales (Orcinus orca), housed in captivity (Marineland park, France). Overall, cetacean skin microbiota is more diverse than planktonic communities and is dominated by different phylogenetic lineages and functions. In addition, the two cetacean species host different skin microbiotas. Within each species, variability was higher between individuals than between body parts, suggesting a high individuality of cetacean skin microbiota. Overall, the skin microbiota of the assessed cetaceans related more to the humpback whale and fishes’ than to microbiotas of terrestrial mammals.