Activation of TLR2 by a small molecule produced by Staphylococcus epidermidis increases antimicrobial defense against bacterial skin infections

The pathogenicity and virulence of the opportunistic pathogen Staphylococcus epidermidis

The pervasive presence of Staphylococcus epidermidis and other coagulase-negative staphylococci on the skin and mucous membranes has long underpinned a casual disregard for the infection risk that these organisms pose to vulnerable patients in healthcare settings. Prior to the recognition of biofilm as an important virulence determinant in S. epidermidis, isolation of this microorganism in diagnostic specimens was often overlooked as clinically insignificant with potential delays in diagnosis and onset of appropriate treatment, contributing to the establishment of chronic infection and increased morbidity or mortality. While impressive progress has been made in our understanding of biofilm mechanisms in this important opportunistic pathogen, research into other virulence determinants has lagged S. aureus. In this review, the broader virulence potential of S. epidermidis including biofilm, toxins, proteases, immune evasion strategies and antibiotic resistance mechanisms is surveyed, together with current and future approaches for improved therapeutic interventions.

Combined metagenomic- and culture-based approaches to investigate bacterial strain-level associations with medication-controlled mild-moderate atopic dermatitis

Background

The skin microbiome is disrupted in atopic dermatitis (AD). Existing research focuses on moderate to severe, unmedicated disease.

Objective

We sought to investigate metagenomic- and culture-based bacterial strain-level differences in mild, medicated AD and the effects these have on human keratinocytes (HKs).

Methods

Skin swabs from anterior forearms were collected from 20 pediatric participants (11 participants with AD sampled at lesional and nonlesional sites and 9 age- and sex-matched controls). Participants had primarily mild to moderate AD and maintained medication use. Samples were processed for microbial metagenomic sequencing and bacterial isolation. Isolates identified as Staphylococcus aureus were tested for enterotoxin production. HK cultures were treated with cell-free conditioned media from representative Staphylococcus species to measure barrier effects.

Results

Metagenomic sequencing identified significant differences in microbiome composition between AD and control groups. Differences were seen at the species and strain levels for Staphylococci, with S aureus found only in participants with AD and differences in Staphylococcus epidermidis strains between control and AD swabs. These strains showed differences in toxin gene presence, which was confirmed in vitro for S aureus enterotoxins. The strain from the participant with the most severe AD produced enterotoxin B levels more than 100-fold higher than the other strains (P < .001). Strains also displayed differential effects on HK metabolism and barrier function.

Conclusions

Strain-level differences in toxin genes from Staphylococcus strains may explain varying effects on HK, with S aureus and non-aureus strains negatively affecting viability and barrier function. These differences are likely important in AD pathogenesis.

Exploring the Multifaceted Therapeutic Potential of Probiotics: A Review of Current Insights and Applications

The interplay between human health and the microbiome has gained extensive attention, with probiotics emerging as pivotal therapeutic agents due to their vast potential in treating various health issues. As significant modulators of the gut microbiota, probiotics are crucial in maintaining intestinal homeostasis and enhancing the synthesis of short-chain fatty acids. Despite extensive research over the past decades, there remains an urgent need for a comprehensive and detailed review that encapsulates probiotics' latest insights and applications. This review focusses on the multifaceted roles of probiotics in promoting health and preventing disease, highlighting the complex mechanisms through which these beneficial bacteria influence both gut flora and the human body at large. This paper also explores probiotics' neurological and gastrointestinal applications, focussing on their significant impact on the gut-brain axis and their therapeutic potential in a broad spectrum of pathological conditions. Current innovations in probiotic formulations, mainly focusing on integrating genomics and biotechnological advancements, have also been comprehensively discussed herein. This paper also critically examines the regulatory landscape that governs probiotic use, ensuring safety and efficacy in clinical and dietary settings. By presenting a comprehensive overview of recent studies and emerging trends, this review aims to illuminate probiotics' extensive therapeutic capabilities, leading to future research and clinical applications. However, besides extensive research, further advanced explorations into probiotic interactions and mechanisms will be essential for developing more targeted and effective therapeutic strategies, potentially revolutionizing health care practices for consumers.

Exploring the nuclear proteins, viral capsid protein, and early antigen protein using immunoinformatic and molecular modeling approaches to design a vaccine candidate against Epstein Barr virus

The available Epstein Barr virus vaccine has tirelessly harnessed the gp350 glycoprotein as its target epitope, but the result has not been preventive. Right here, we designed a global multi-epitope vaccine for EBV; with special attention to making sure all strains and preventive antigens are covered. Using a robust computational vaccine design approach, our proposed vaccine is armed with 6-16 mers linear B-cell epitopes, 4-9 mer CTL epitopes, and 8-15 mer HTL epitopes which are verified to induce interleukin 4, 10 & IFN-gamma. We employed deep computational mining coupled with expert intelligence in designing the vaccine, using human Beta defensin-3-which has been reported to induce the same TLRs as EBV-as the adjuvant. The tendency of the vaccine to cause autoimmune disorder is quenched by the assurance that the construct contains no EBNA-1 homolog. The protein vaccine construct exhibited excellent physicochemical attributes such as Aliphatic index 59.55 and GRAVY - 0.710; and a ProsaWeb Z score of - 3.04. Further computational analysis revealed the vaccine docked favorably with EBV indicted TLR 1, 2, 4 & 9 with satisfactory interaction patterns. With global coverage of 85.75% and the stable molecular dynamics result obtained for the best two interactions, we are optimistic that our nontoxic, non-allergenic multi-epitope vaccine will help to ameliorate the EBV-associated diseases-which include various malignancies, tumors, and cancers-preventively.

Alcaligenes faecalis corrects aberrant matrix metalloproteinase expression to promote reepithelialization of diabetic wounds

Chronic wounds are a common and costly complication of diabetes, where multifactorial defects contribute to dysregulated skin repair, inflammation, tissue damage, and infection. We previously showed that aspects of the diabetic foot ulcer microbiota were correlated with poor healing outcomes, but many microbial species recovered remain uninvestigated with respect to wound healing. Here, we focused on Alcaligenes faecalis, a Gram-negative bacterium that is frequently recovered from chronic wounds but rarely causes infection. Treatment of diabetic wounds with A. faecalis accelerated healing during early stages. We investigated the underlying mechanisms and found that A. faecalis treatment promotes reepithelialization of diabetic keratinocytes, a process that is necessary for healing but deficient in chronic wounds. Overexpression of matrix metalloproteinases in diabetes contributes to failed epithelialization, and we found that A. faecalis treatment balances this overexpression to allow proper healing. This work uncovers a mechanism of bacterial-driven wound repair and provides a foundation for the development of microbiota-based wound interventions.

Environmental factors and host sex influence the skin microbiota structure of Hong Kong newt (Paramesotriton hongkongensis) in a coldspot of chytridiomycosis in subtropical East Asia

Chytridiomycosis, an infectious skin disease caused by the chytrid fungi, Batrachochytrium dendrobatidis and B. salamandrivorans, poses a significant threat to amphibian biodiversity worldwide. Antifungal bacteria found on the skin of chytrid-resistant amphibians could potentially provide defense against chytridiomycosis and lower mortality rates among resistant individuals. The Hong Kong newt (Paramesotriton hongkongensis) is native to East Asia, a region suspected to be the origin of chytrids, and has exhibited asymptomatic infection, suggesting a long-term coexistence with the chytrids. Therefore, the skin microbiota of this resistant species warrant investigation, along with other factors that can affect the microbiota. Among the 149 newts sampled in their natural habitats in Hong Kong, China, putative antifungal bacteria were found in all individuals. There were 314 amplicon sequence variants distributed over 25 genera of putative antifungal bacteria; abundant ones included Acinetobacter, Flavobacterium, and Novosphingobium spp. The skin microbiota compositions were strongly influenced by the inter-site geographical distances. Despite inter-site differences, we identified some core skin microbes across sites that could be vital to P. hongkongensis. The dominant cores included the family Comamonadaceae, family Chitinophagaceae, and class Betaproteobacteria. Moreover, habitat elevation and host sex also exhibited significant effects on skin microbiota compositions. The antifungal bacteria found on these newts offer an important resource for conservation against chytridiomycosis, such as developing probiotic treatments for susceptible species.

Correlation between the facial skin microbiome and sensitive skin using the 2bRAD-M technique

OBJECTIVE

This study aimed to expound on the correlation between facial skin microbiome and sensitive skin (SS) using a novel sequencing technique.

METHODS

We applied the 2bRAD sequencing for the microbiome, which enables accurate characterization of the low-biomass microbiome at species resolution to profile facial skin microbes in SS and non-SS groups. Further, the bacterial colonies were isolated and cultured from skin surfaces to study the pro-inflammatory effect on human keratinocytes by ELISA.

RESULTS

We accordingly identified 1142 genera and 4436 strains. In the SS group, the proportions of Actinomyces and Microbotryomycetes were significantly increased, whereas that of Acidimicrobiia was decreased. Kruskal-Wallis analysis revealed significant differences in 11 genera and 35 species, among which the proportions of Dermabacter, Chryseobacterium, Rhodotorula and Peptoniphilus A were increased in the SS group. Analysis of the top 10 genera revealed increased proportions of Cutibacterium, Corynebacterium and Staphylococcus. Moreover, the proportion of Dermabacter hominis was significantly increased by 18.9-fold in the SS group, whereas those of many Streptococcus strains were significantly decreased. Focus on the isolated bacterial colonies from skin surfaces, more yellow colonies were found in SS group when cultured in Tryptic Soy Broth medium for 48 h, and more interleukin-8 was detected on keratinocytes after yellow colonies stimulation, such as S.capitis, M.luteus.

CONCLUSIONS

This study suggests that more SS-associated microorganisms can be identified using the 2bRAD technique even with a small sample size. Dermabacter hominis and Chryseobacterium was firstly reported with a significantly increase in SS, and the S.capitis, as well as M.luteus, but not S.aureus, may be associated with skin inflammation.

The past, present and future of polymicrobial infection research: Modelling, eavesdropping, terraforming and other stories

Over the last two centuries, great advances have been made in microbiology as a discipline. Much of this progress has come about as a consequence of studying the growth and physiology of individual microbial species in well-defined laboratory media; so-called "axenic growth". However, in the real world, microbes rarely live in such "splendid isolation" (to paraphrase Foster) and more often-than-not, share the niche with a plethora of co-habitants. The resulting interactions between species (and even between kingdoms) are only very poorly understood, both on a theoretical and experimental level. Nevertheless, the last few years have seen significant progress, and in this review, we assess the importance of polymicrobial infections, and show how improved experimental traction is advancing our understanding of these. A particular focus is on developments that are allowing us to capture the key features of polymicrobial infection scenarios, especially as those associated with the human airways (both healthy and diseased).

The epidermal lipid-microbiome loop and immunity: Important players in atopic dermatitis

BACKGROUND

The promotion of epidermal barrier dysfunction is attributed to abnormalities in the lipid-microbiome positive feedback loop which significantly influences the imbalance of the epithelial immune microenvironment (EIME) in atopic dermatitis (AD). This imbalance encompasses impaired lamellar membrane integrity, heightened exposure to epidermal pathogens, and the regulation of innate and adaptive immunity. The lipid-microbiome loop is substantially influenced by intense adaptive immunity which is triggered by abnormal loop activity and affects the loop's integrity through the induction of atypical lipid composition and responses to dysregulated epidermal microbes. Immune responses participate in lipid abnormalities within the EIME by downregulating barrier gene expression and are further cascade-amplified by microbial dysregulation which is instigated by barrier impairment.

AIM OF REVIEW

This review examines the relationship between abnormal lipid composition, microbiome disturbances, and immune responses in AD while progressively substantiating the crosstalk mechanism among these factors. Based on this analysis, the "lipid-microbiome" positive feedback loop, regulated by immune responses, is proposed.

KEY SCIENTIFIC CONCEPTS OF REVIEW

The review delves into the impact of adaptive immune responses that regulate the EIME, driving AD, and investigates potential mechanisms by which lipid supplementation and probiotics may alleviate AD through the up-regulation of the epidermal barrier and modulation of immune signaling. This exploration offers support for targeting the EIME to attenuate AD.

Recent advances in understanding the role of the skin microbiome in the treatment of atopic dermatitis

The skin is the largest organ in the human body, and histologically consists of the epidermis, dermis and subcutaneous tissue. Humans maintain a cooperative symbiotic relationship with their skin microbiota, a complex community of bacteria, fungi and viruses that live on the surface of the skin, and which act as a barrier to protect the body from the inside and outside. The skin is a 'habitat' and vast 'ecosystem' inhabited by countless microbes; as such, relationships have been forged through millions of years of coevolution. It is not surprising then that microbes are key participants in shaping and maintaining essential physiological processes. In addition to maintaining barrier function, the unique symbiotic microbiota that colonizes the skin increases the immune response and provides protection against pathogenic microbes. This review examines our current understanding of skin microbes in shaping and enhancing the skin barrier, as well as skin microbiome-host interactions and their roles in skin diseases, such as atopic dermatitis (AD). We also report on the current status of AD therapeutic drugs that target the skin microbiome, related research on current therapeutic strategies, and the limitations and future considerations of skin microbiome research. In particular, as a future strategy, we discuss the need for a skin-on-a-chip-based microphysiological system research model amenable to biomimetic in vitro studies and human skin equivalent models, including skin appendages.

Skin microbiome bacteria enriched following long sun exposure can reduce oxidative damage

Sun exposure is harmful to the skin and increases the risk of skin aging and skin cancer. Here we examined the effects of daily exposure to sun radiation on the skin microbiome in order to determine whether skim microbiome bacteria can contribute to protection from solar damage. Skin swabs were collected from ten lifeguards before and after the summer to analyse the skin microbiome. The results indicate that specific skin microbiome bacteria were enriched following the seasonal sun exposure. Especially interesting were two bacterial families - Sphingomonas and Erythrobacteraceae - which may have the ability to protect against UV radiation as they produce potentially protective compounds. We concentrated on a Sphingomonas strain and could show that it was highly resistant to UV irradiation and was able to reduce reactive oxygen species levels in human keratinocytes. These results provide a proof-of-concept for the role of the skin microbiome in protection from solar radiation.

Thermal Therapy Modulation of the Psoriasis-Associated Skin and Gut Microbiome

INTRODUCTION

Psoriasis is a systemic immune-mediated disease primarily manifesting as skin redness and inflammation. Balneotherapy proved to be a successful non-pharmacological option to reduce the skin areas affected by the disease, but the specific mechanisms underlying this effect have not been elucidated yet. Here we test the hypothesis that the effect of thermal treatments on psoriatic lesions could be partially mediated by changes in the resident microbial population, i.e., the microbiome.

METHODS

In this study, we enrolled patients with psoriasis and monitored changes in their skin and gut microbiome after a 12-bath balneotherapy course with a combination of 16S rRNA amplicon sequencing and metagenomics. Changes in the resident microbiome were then correlated with thermal therapy outcomes evaluated as changes in Psoriasis Area and Severity Index (PASI) and Body Surface Area index (BSA).

RESULTS

The amplicon sequencing analysis of the skin microbiome showed that after thermal treatment the microbiome composition of affected areas improved to approach that typical of unaffected skin. We moreover identified some low-abundance bacterial biomarkers indicative of disease status and treatment efficacy, and we showed via metagenomic sequencing that thermal treatments and thermal water drinking affect the fecal microbiome to host more species associated with favorable metabolic health.

CONCLUSIONS

Changes in lower-abundance microbial taxa presence and abundance could be the basis for the positive effect of thermal water treatment and drinking on the cutaneous and systemic symptomatology of psoriasis.

Skin microbiota secretomes modulate cutaneous innate immunity against Borrelia burgdorferi s.s

In Lyme borreliosis, the skin constitutes a major interface for the host, the bacteria and the tick. Skin immunity is provided by specialized immune cells but also by the resident cells: the keratinocytes and the fibroblasts. Discoveries on the role of the microbiome in the modulation of skin inflammation and immunity have reinforced the potential importance of the skin in vector-borne diseases. In this study, we analyzed in vitro the interaction of human primary keratinocytes and fibroblasts with Borrelia burgdorferi sensu stricto N40 in presence or absence of bacterial commensal supernatants. We aimed to highlight the role of resident skin cells and skin microbiome on the inflammation induced by B. burgdorferi s.s.. The secretomes of Staphylococcus epidermidis, Corynebacterium striatum and Cutibacterium acnes showed an overall increase in the expression of IL-8, CXCL1, MCP-1 and SOD-2 by fibroblasts, and of IL-8, CXCL1, MCP-1 and hBD-2 in the undifferentiated keratinocytes. Commensal bacteria showed a repressive effect on the expression of IL-8, CXCL1 and MCP-1 by differentiated keratinocytes. Besides the inflammatory effect observed in the presence of Borrelia on all cell types, the cutaneous microbiome appears to promote a rapid innate response of resident skin cells during the onset of Borrelia infection.

The influence of dietary patterns on skin bacterial diversity, composition, and co-occurrence relationships at forearm and neck sites of healthy Korean adults

AIMS

Diet and nutrition are important aspects of skin physiology and health. However, the influence of diet on the bacterial flora of different skin sites is not well understood. Therefore, we investigated the relationship between dietary patterns (DPs) and skin bacterial flora on the forearm (a dry site) and the neck (a sebaceous site) of healthy Korean adults.

METHODS AND RESULTS

In metagenomics analysis, Shannon and Simpson indices were higher on the forearm than on the neck and were negatively correlated with the two dominant species, Cutibacterium acnes and Staphylococcus epidermidis, on two skin sites. In addition, the Simpson index of the forearm was positively associated with DP1 (characterized by a high intake of vegetables, mushrooms, meat, fish and shellfish, seaweed, and fat and oil), while that on the neck was negatively associated with DP2 (characterized by a high intake of fast food). A high intake of DP1 was associated with a lower abundance of dominant species, including C. acnes, and higher degrees of the co-occurrence network, whereas a high intake of DP2 was associated with the opposite pattern.

CONCLUSIONS

Specific diets may impact both skin bacterial diversity and composition, as well as the co-occurrence of bacteria, which may vary across different skin sites.

Induction of IL-32 in the immune response of keratinocytes to Mycobacterium marinum infection

Keratinocytes are the predominant cell type in the skin epidermis, and they not only protect the skin from the influence of external physical factors but also function as an immune barrier against microbial invasion. However, little is known regarding the immune defence mechanisms of keratinocytes against mycobacteria. Here, we performed single-cell RNA sequencing (scRNA-seq) on skin biopsy samples from patients with Mycobacterium marinum infection and bulk RNA sequencing (bRNA-seq) on M. marinum-infected keratinocytes in vitro. The combined analysis of scRNA-seq and bRNA-seq data revealed that several genes were upregulated in M. marinum-infected keratinocytes. Further in vitro validation of these genes by quantitative polymerase chain reaction and western blotting assay confirmed the induction of IL-32 in the immune response of keratinocytes to M. marinum infection. Immunohistochemistry also showed the high expression of IL-32 in patients' lesions. These findings suggest that IL-32 induction is a possible mechanism through which keratinocytes defend against M. marinum infection; this could provide new targets for the immunotherapy of chronic cutaneous mycobacterial infections.

Emerging Trends and Focus in Human Skin Microbiome Over the Last Decade: A Bibliometric Analysis and Literature Review

Background

Human skin microbiome is the first barrier against exogenous attack and is associated with various skin disease pathogenesis and progression. Advancements in high-throughput sequencing technologies have paved the way for a deeper understanding of this field. Based on the bibliometric analysis, this investigation aimed to identify the hotspots and future research trends associated with human skin microbiomes studied over the past decade.

Methods

The published research on skin microbiome from January 2013 to January 2023 was retrieved from the Web of Science Core Collection. Data cleaning processes to ensure robust data and the bibliometrix packages R, CiteSpace, VOSviewer, Origin, and Scimago Graphica for bibliometric and visual analyses were utilized.

Results

A total of 1629 published documents were analyzed. The overall publication trend steadily increased, with relatively fast growth in 2017 and 2020. The United States of America has the highest number of publications and citations and shows close collaborations with China and Germany. The University of California, San Diego, indicated a higher number of publications than other institutions and the fastest growth rate. The top three most publishing journals on this topic are Microorganisms, Frontiers in Microbiology, and Experimental dermatology. Gallo RL is the most influential author with the highest h- and g-index and most publications in skin microecology, followed by Grice EA and Kong HH. The top 10 most frequently used keywords in recent years included skin microbiome, microbiome, staphylococcus aureus, diversity, atopic dermatitis, skin, bacteria, infections, gut microbiota, and disease.

Conclusion

The skin microbiome is an area of research that requires continuous analysis, and even with much-achieved progress, future research will further be aided as technology develops.

The feline skin microbiome: interrelationship between health and disease

PRACTICAL RELEVANCE

As with other species, the skin microbiome of cats has been assessed over the past few years utilizing modern technologies. This has resulted in the identification of many more bacterial and fungal organisms compared with what had been recorded historically on the skin in various states of health and disease using culture-based studies. This information is expanding the knowledge of how microbial communities are impacted by various changes in the skin health of cats. More specifically, how these microbial communities change in the face of health and disease, and how various therapeutic interventions affect the cutaneous microbiome, lends a greater understanding of disease pathogenesis and provides a growing area of research for correcting dysbiosis and improving feline skin health.

EVIDENCE BASE

Most studies on the feline skin microbiome thus far have been descriptive in nature. These provide a framework for the next level of investigations on how various states of health and disease impact the products produced by the cutaneous microbiome (ie, the cutaneous metabolome), as well as how targeted interventions may promote the restoration of balance.

AIMS

This review aims to summarize what is currently known about the feline cutaneous microbiome and its clinical implications. The role of the skin microbiome in health and disease, the current state of research in this area and the potential for future studies to produce targeted interventions for cats are a particular focus.

Human skin bacterial microbiota homeostasis: A delicate balance between health and disease

As the largest organ of the body, the skin acts as a barrier to prevent diseases and harbors a variety of beneficial bacteria. Furthermore, the skin bacterial microbiota plays a vital role in health and disease. Disruption of the barrier or an imbalance between symbionts and pathogens can lead to skin disorders or even systemic diseases. In this review, we first provide an overview of research on skin bacterial microbiota and human health, including the composition of skin bacteria in a healthy state, as well as skin bacterial microbiota educating the immune system and preventing the invasion of pathogens. We then discuss the diseases that result from skin microbial dysbiosis, including atopic dermatitis, common acne, chronic wounds, psoriasis, viral transmission, cutaneous lupus, cutaneous lymphoma, and hidradenitis suppurativa. Finally, we highlight the progress that utilizes skin microorganisms for disease therapeutics, such as bacteriotherapy and skin microbiome transplantation. A deeper knowledge of the interaction between human health and disease and the homeostasis of the skin bacterial microbiota will lead to new insights and strategies for exploiting skin bacteria as a novel therapeutic target.

Staphylococcus epidermidis isolates from atopic or healthy skin have opposite effect on skin cells: potential implication of the AHR pathway modulation

Introduction

Staphylococcus epidermidis is a commensal bacterium ubiquitously present on human skin. This species is considered as a key member of the healthy skin microbiota, involved in the defense against pathogens, modulating the immune system, and involved in wound repair. Simultaneously, S. epidermidis is the second cause of nosocomial infections and an overgrowth of S. epidermidis has been described in skin disorders such as atopic dermatitis. Diverse isolates of S. epidermidis co-exist on the skin. Elucidating the genetic and phenotypic specificities of these species in skin health and disease is key to better understand their role in various skin conditions. Additionally, the exact mechanisms by which commensals interact with host cells is partially understood. We hypothesized that S. epidermidis isolates identified from different skin origins could play distinct roles on skin differentiation and that these effects could be mediated by the aryl hydrocarbon receptor (AhR) pathway.

Methods

For this purpose, a library of 12 strains originated from healthy skin (non-hyperseborrheic (NH) and hyperseborrheic (H) skin types) and disease skin (atopic (AD) skin type) was characterized at the genomic and phenotypic levels.

Results and discussion

Here we showed that strains from atopic lesional skin alter the epidermis structure of a 3D reconstructed skin model whereas strains from NH healthy skin do not. All strains from NH healthy skin induced AhR/OVOL1 path and produced high quantities of indole metabolites in co-culture with NHEK; especially indole-3-aldehyde (IAld) and indole-3-lactic acid (ILA); while AD strains did not induce AhR/OVOL1 path but its inhibitor STAT6 and produced the lowest levels of indoles as compared to the other strains. As a consequence, strains from AD skin altered the differentiation markers FLG and DSG1. The results presented here, on a library of 12 strains, showed that S. epidermidis originated from NH healthy skin and atopic skin have opposite effects on the epidermal cohesion and structure and that these differences could be linked to their capacity to produce metabolites, which in turn could activate AHR pathway. Our results on a specific library of strains provide new insights into how S. epidermidis may interact with the skin to promote health or disease.

Butyrate inhibits Staphylococcus aureus-aggravated dermal IL-33 expression and skin inflammation through histone deacetylase inhibition

Atopic dermatitis (AD) is an inflammatory skin disease caused by the disruption of skin barrier, and is dominated by the type 2 immune responses. Patients with AD have a high risk of developing Staphylococcus aureus infection. Interleukin-33 (IL-33), an alarmin, has been implicated in the pathophysiology of AD development. Butyrate, a short chain fatty acid known to be produced from the fermentation of glycerol by the commensal skin bacterium, Staphylococcus epidermidis, has been reported to possess antimicrobial and anti-inflammatory properties that suppress inflammatory dermatoses. However, little is known about the effects of butyrate on dermal IL-33 expression and associated immune response in S. aureus-aggravated skin inflammation in the context of AD. To decipher the underlying mechanism, we established an AD-like mouse model with epidermal barrier disruption by delipidizing the dorsal skin to induce AD-like pathophysiology, followed by the epicutaneous application of S. aureus and butyrate. We discovered that S. aureus infection exacerbated IL-33 release from keratinocytes and aggravated dermal leukocyte infiltration and IL-13 expression. Moreover, we showed that butyrate could attenuate S. aureus-aggravated skin inflammation with decreased IL-33, IL-13, and leukocyte infiltration in the skin. Mechanistically, we demonstrated that butyrate suppressed IL-33 expression and ameliorated skin inflammation through histone deacetylase 3 (HDAC3) inhibition. Overall, our findings revealed the potential positive effect of butyrate in controlling inflammatory skin conditions in AD aggravated by S. aureus infection.

Dynamic Distribution of Skin Microorganisms in Donkeys at Different Ages and Various Sites of the Body

Considerable evidence suggests that the skin microbiota is not only important and complex in humans and other mammals but also critical for maintaining health and skin homeostasis. To date, studies on the skin microorganisms of donkeys are surprisingly rare. To investigate the dynamic changes in commensal microbial communities on the skins of healthy donkeys throughout the growing period, skin and soil samples were collected from 30 healthy Dezhou donkeys (ranging from 1, 6, 12, 24 to 48 months of age) and their corresponding breeding sheds on the farm. All samples were analysed for high-throughput sequencing of the 16S rRNA and ITS to characterize the skin microbiota of healthy donkeys and compare the differences in skin microbiota among donkeys of different ages. There were notable differences in the proportions of various genera (including bacteria and fungi) between dorsal and abdominal skin with increasing age. The comparison of the skin microbial communities among these groups revealed that Staphylococcus was mainly enriched in the early growing stage (1 and 6 months), while the relative abundance of Streptococcus was higher in both the 1- and 48-month-old age groups. Moreover, some bacteria and commensal fungi, such as Staphylococcus and Trichosporon, were found to be positively correlated between the skin and the environment. This is the first study to investigate the dynamic changes in skin microbiota diversity and composition in donkeys of different ages and at different sites of the body. Furthermore, this study provides insights into the dynamic alterations in skin microbes during a donkey's growth and characterizes the profiles of bacterial and fungal communities across a donkey's body regions (dorsal and abdomen).

Skin microbiome bacteria enriched following long sun exposure can reduce oxidative damage: a 5-month preliminary study of ten lifeguards

BACKGROUND

The skin microbiome is important for skin health and protection against solar damage. Sun exposure can cause long-term harm and increase the risk of skin aging and skin cancer. Here we examined the effects of daily exposure to sun radiation on the skin microbiome in order to determine whether skin microbiome bacteria can contribute to protection from solar damage.

METHODS

Skin swabs were collected from ten lifeguards before and after the summer season to analyze changes in the skin microbiome. The bacteria which were enriched after the summer were chosen for further studies to assess their response to solar radiation and potential effect on skin health.

RESULT

The study indicates that specific skin microbiome bacteria were enriched after seasonal sun exposure. Two of these, Sphingomonas and Erythrobacteraceae, may have the ability to protect against UV radiation as they produce potentially protective compounds. Indeed, further analysis showed that a Sphingomonas spp. was able to reduce reactive oxygen species levels in human keratinocytes.

CONCLUSION

These results suggest that members of the skin microbiome can enhance protection from solar radiation damage and contribute to human health. The findings provide a proof-of-concept for the role of the skin microbiome in promoting skin health.

Extracellular vesicles of commensal skin microbiota alleviate cutaneous inflammation in atopic dermatitis mouse model by reestablishing skin homeostasis

Atopic dermatitis (AD) is a chronic inflammatory cutaneous disorder in which the skin is affected by microbial dysbiosis. The role of commensal skin microbiota in AD is of great interest. Extracellular vesicles (EVs) are important regulators of skin homeostasis and pathology. The mechanism of preventing AD pathogenesis via commensal skin microbiota-derived EVs remains poorly understood. In this study, we investigated the role of commensal skin bacterium Staphylococcus epidermidis-derived EVs (SE-EVs). We showed that SE-EVs significantly decreased the expression of proinflammatory genes (TNF-α, IL-1β, IL-6, IL-8 and iNOS) via lipoteichoic acid and increased the proliferation and migration of calcipotriene (MC903)-treated HaCaT cells. Furthermore, SE-EVs increased the expression of human β-defensins 2 and 3 in MC903-treated HaCaT cells via Toll-like receptor 2, enhancing resistance to Staphylococcus aureus growth. In addition, topical SE-EV application remarkably attenuated inflammatory cell infiltration (CD4⁺ T cells and Gr1⁺ cells), T_H2 cytokine gene expression (IL-4, IL-13 and TLSP), and IgE levels in MC903-induced AD-like dermatitis mice. Intriguingly, SE-EVs induced IL-17A⁺ CD8⁺ T-cell accumulation in the epidermis, which may represent heterologous protection. Taken together, our findings showed that SE-EVs reduced AD-like skin inflammation in mice and may potentially be a bioactive nanocarrier for the treatment of AD.

Production of a selective antibacterial fatty acid against Staphylococcus aureus by Bifidobacterium strains

Aims: C16 monounsaturated fatty acid (C16:1) show antibacterial activity against Staphylococcus aureus, a pathogen associated with various diseases such as atopic dermatitis and bacteremia, while the compound does not exhibit antibacterial activity against Staphylococcus epidermidis, an epidermal commensal that inhibits the growth of S. aureus. In this study, we aimed to find bifidobacterial strains with the ability to produce C16:1 and to find a practical manner to utilize C16:1-producing strains in industry. Methods: Various Bifidobacterium strains were screened for their content of C16:1. The chemical identity of C16:1 produced by a selected strain was analyzed by gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS). Medium components that affect the C16:1 content of the selected strain were investigated. Antibacterial activity against staphylococci was compared between the authentic C16:1 isomers and total fatty acids (TFA) extracted from the selected strain. Results: B. adolescentis 12451, B. adolescentis 12-111, B. boum JCM 1211, and Bifidobacterium sp. JCM 7042 showed high C16:1 content among the tested strains. TFA extracted from Bifidobacterium sp. JCM 7042 contained C16:1 at 2.3% as the fatty acid constituent (2.4 mg/L of broth). Through GC-MS and LC-MS analyses, the C16:1 synthesized by Bifidobacterium sp. JCM 7042 was identified as 7-cis-hexadecenoic acid (7-cis-C16:1). The authentic 7-cis-C16:1 showed strong and selective antibacterial activity against S. aureus, similar to 6-cis-C16:1, with a minimum inhibitory concentration (MIC) of < 10 µg/mL. Components that increase C16:1 productivity were not found in the MRS and TOS media; however, Tween 80 was shown to considerably reduce the C16:1 ratio in TFA. Antibacterial activity against S. aureus was observed when the TFA extracted from Bifidobacterium sp. JCM 7042 contained high level of 7-cis-C16:1 (6.1% in TFA) but not when it contained low level of 7-cis-C16:1 (0.1% in TFA). Conclusion: The fatty acid, 7-cis-C16:1, which can selectively inhibit the S. aureus growth, is accumulated in TFA of several bifidobacteria. The TFA extracted from cultured cells of Bifidobacterium sp. JCM 7042 demonstrated antibacterial activity. From a practical viewpoint, our findings are important for developing an efficient method to produce novel skin care cosmetics, functional dairy foods, and other commodities.

Skin programming of inflammatory responses to Staphylococcus aureus is compartmentalized according to epidermal keratinocyte differentiation status

BACKGROUND

Acute cutaneous inflammation causes microbiome alterations as well as ultrastructural changes in epidermis stratification. However, the interactions between keratinocyte proliferation and differentiation status and the skin microbiome have not been fully explored.

OBJECTIVES

Hypothesizing that the skin microbiome contributes to regulation of keratinocyte differentiation and can modify antimicrobial responses, we examined the effect of exposure to commensal (Staphylococcus epidermidis, SE) or pathogenic (Staphylococcus aureus, SA) challenge on epidermal models.

METHODS

Explant biopsies were taken to investigate species-specific antimicrobial effects of host factors. Further investigations were performed in reconstituted epidermal models by bulk transcriptomic analysis alongside secreted protein profiling. Single-cell RNA sequencing analysis was performed to explore the keratinocyte populations responsible for SA inflammation. A dataset of 6391 keratinocytes from control (2044 cells), SE challenge (2028 cells) and SA challenge (2319 cells) was generated from reconstituted epidermal models.

RESULTS

Bacterial lawns of SA, not SE, were inhibited by human skin explant samples, and microarray analysis of three-dimensional epidermis models showed that host antimicrobial peptide expression was induced by SE but not SA. Protein analysis of bacterial cocultured models showed that SA exposure induced inflammatory mediator expression, indicating keratinocyte activation of other epidermal immune populations. Single-cell DropSeq analysis of unchallenged naive, SE-challenged and SA-challenged epidermis models was undertaken to distinguish cells from basal, spinous and granular layers, and to interrogate them in relation to model exposure. In contrast to SE, SA specifically induced a subpopulation of spinous cells that highly expressed transcripts related to epidermal inflammation and antimicrobial response. Furthermore, SA, but not SE, specifically induced a basal population that highly expressed interleukin-1 alarmins.

CONCLUSIONS

These findings suggest that SA-associated remodelling of the epidermis is compartmentalized to different keratinocyte populations. Elucidating the mechanisms regulating bacterial sensing-triggered inflammatory responses within tissues will enable further understanding of microbiome dysbiosis and inflammatory skin diseases, such as atopic eczema.

Probiotics in dermatological and cosmetic products – application and efficiency

The term “probiotics” has first been used in 1907 by Elie Metchnikoff. Since then, probiotics have been part of research not only in regards of digestive health, but also inflammatory diseases. Lately, there has been an increased interest of probiotic’s effects in skincare. The management of atopic dermatitis, acne, psoriasis, photo aging, skin cancer, intimate care, oral care, wound healing is getting harder each passing day, due to increased antibiotic resistance and other side effects of conventional therapy. Therefore, new ingredients have been investigated and probiotics have been proved to be effective in treating various skin conditions. This review aims to evaluate the scientific evidence on topical and oral probiotics, and to evaluate the efficacy of cosmetic and dermatological products containing probiotics. Many studies have shown that skin and gut microbiome alterations have an important role in skin health. Although this is a new topic in dermatology and cosmetology, there have been some promising results in lots of research studies that the use of probiotics in cosmetic products may help improve the patient’s outcome. While oral probiotics have been shown to promote gut health, which influences the host immune system and helps treat different skin diseases, the mechanism of action of topical probiotics is not yet fully understood. Although the number of commercial probiotic cosmetic products released in the market is increasing and most of the studies have not shown any serious side effect of probiotics, further studies, in larger and heterogeneous groups are needed.

Exposure to isocyanates predicts atopic dermatitis prevalence and disrupts therapeutic pathways in commensal bacteria

Atopic dermatitis (AD) is a chronic inflammatory skin condition increasing in industrial nations at a pace that suggests environmental drivers. We hypothesize that the dysbiosis associated with AD may signal microbial adaptations to modern pollutants. Having previously modeled the benefits of health-associated Roseomonas mucosa, we now show that R. mucosa fixes nitrogen in the production of protective glycerolipids and their ceramide by-products. Screening EPA databases against the clinical visit rates identified diisocyanates as the strongest predictor of AD. Diisocyanates disrupted the production of beneficial lipids and therapeutic modeling for isolates of R. mucosa as well as commensal Staphylococcus. Last, while topical R. mucosa failed to meet commercial end points in a placebo-controlled trial, the subgroup who completed the full protocol demonstrated sustained, clinically modest, but statistically significant clinical improvements that differed by study site diisocyanate levels. Therefore, diisocyanates show temporospatial and epidemiological association with AD while also inducing eczematous dysbiosis.

Large-Scale CRISPRi and Transcriptomics of Staphylococcus epidermidis Identify Genetic Factors Implicated in Lifestyle Versatility

Staphylococcus epidermidis is a ubiquitous human commensal skin bacterium that is also one of the most prevalent nosocomial pathogens. The genetic factors underlying this remarkable lifestyle plasticity are incompletely understood, mainly due to the difficulties of genetic manipulation, precluding high-throughput functional profiling of this species. To probe the versatility of S. epidermidis to survive across a diversity of environmental conditions, we developed a large-scale CRISPR interference (CRISPRi) screen complemented by transcriptional profiling (RNA sequencing) across 24 diverse conditions and piloted a droplet-based CRISPRi approach to enhance throughput and sensitivity. We identified putative essential genes, importantly revealing amino acid metabolism as crucial to survival across diverse environments, and demonstrated the importance of trace metal uptake for survival under multiple stress conditions. We identified pathways significantly enriched and repressed across our range of stress and nutrient-limited conditions, demonstrating the considerable plasticity of S. epidermidis in responding to environmental stressors. Additionally, we postulate a mechanism by which nitrogen metabolism is linked to lifestyle versatility in response to hyperosmotic challenges, such as those encountered on human skin. Finally, we examined the survival of S. epidermidis under acid stress and hypothesize a role for cell wall modification as a vital component of the survival response under acidic conditions. Taken together, this study integrates large-scale CRISPRi and transcriptomics data across multiple environments to provide insights into a keystone member of the human skin microbiome. Our results additionally provide a valuable benchmarking analysis for CRISPRi screens and are a rich resource for other staphylococcal researchers. IMPORTANCE Staphylococcus epidermidis is a bacteria that broadly inhabits healthy human skin, yet it is also a common cause of skin infections and bloodstream infections associated with implanted medical devices. Because human skin has many different types of S. epidermidis, each containing different genes, our goal is to determine how these different genes allow S. epidermidis to switch from healthy growth in the skin to being an infectious pathogen. Understanding this switch is critical to developing new strategies to prevent and treat S. epidermidis infections.

Genetic/Environmental Contributions and Immune Dysregulation in Children with Atopic Dermatitis

Atopic dermatitis (AD) is one of the most common skin conditions in humans. AD affects up to 20% of children worldwide and results in morbidity for both patients and their caregivers. The basis of AD is an interplay between genetics and the environment characterized by immune dysregulation. A myriad of mutations that compromise the skin barrier and/or immune function have been linked to AD. Of these, filaggrin gene (FLG) mutations are the most evidenced. Many other mutations have been implicated in isolated studies that are often unreplicated, creating an archive of genes with potential but unconfirmed relevance to AD. Harnessing big data, polygenic risk scores (PRSs) and genome-wide association studies (GWAS) may provide a more practical strategy for identifying the genetic signatures of AD. Epigenetics may also play a role. Staphylococcus aureus is the most evidenced microbial contributor to AD. Cutaneous dysbiosis may result in over-colonization by pathogenic strains and aberrant skin immunity and inflammation. Aeroallergens, air pollution, and climate are other key environmental contributors to AD. The right climate and/or commensals may improve AD for some patients.

Innovations in Therapeutic Improvement of the Cutaneous Microbiome in Children with Atopic Dermatitis

Biofilm is the dominant form of skin microbiota organization that provides adhesion and preservation of microorganisms in the skin micro-environment. It is necessary to ensure epidermal barrier function and local immunomodulation. Staphylococcus aureus becomes the major colonizer of skin lesions in case of atopic dermatitis exacerbation, and it also can form the biofilms. S. aureus growth and biofilm formation due to other microbial commensals on the skin of patients with atopic dermatitis leads to chronic output of pro-inflammatory cytokines and later to abnormalities in healthy skin microbiome. The role of microbial biofilm in human’s health makes the skin microbiota an attractive target for therapeutic intervention in various skin diseases.

Skin Barrier Function and the Microbiome

Human skin is the largest organ and serves as the first line of defense against environmental factors. The human microbiota is defined as the total microbial community that coexists in the human body, while the microbiome refers to the collective genome of these microorganisms. Skin microbes do not simply reside on the skin but interact with the skin in a variety of ways, significantly affecting the skin barrier function. Here, we discuss recent insights into the symbiotic relationships between the microbiome and the skin barrier in physical, chemical, and innate/adaptive immunological ways. We discuss the gut-skin axis that affects skin barrier function. Finally, we examine the effects of microbiome dysbiosis on skin barrier function and the role of these effects in inflammatory skin diseases, such as acne, atopic dermatitis, and psoriasis. Microbiome cosmetics can help restore skin barrier function and improve these diseases.

Gallomyrtucommulones G and H, New Phloroglucinol Glycosides, from Bioactive Fractions of Myrtus communis against Staphylococcus Species

Myrtaceae family is a continuous source of antimicrobial agents. In the search for novel antimicrobial agents against Staphylococcus species, bioactive fractions of Myrtus communis L., growing in the Sardinia island (Italy) have been investigated. Their phytochemical analysis led us to isolate and characterize four alkylphloroglucinol glycosides (1–4), three of them gallomyrtucommulones G–H (1,2), and myrtucommulonoside (4) isolated and characterized for the first time. The structures of the new and known compounds, endopreroxide G3 (5), myricetin-3-O-glycosides (6,7) were determined based on the spectroscopic evidence including 1D-/2D-NMR and HR-MS spectrometry. Enriched fractions as well as pure compounds were tested for their antimicrobial activity by broth micro-dilution assay against Staphylococcus epidermidis and S. aureus. Results reported herein demonstrated that gallomyrtucommulone G (1) showed a selective antimicrobial activity against both S. aureus strains (ATCC 29213 and 43300) until 16 μg/mL while gallomyrtucommulone D (3) showed the best growth inhibition value at 64 μg/mL.

Controlling skin microbiome as a new bacteriotherapy for inflammatory skin diseases

The skin serves as the interface between the human body and the environment and interacts with the microbial community. The skin microbiota consists of microorganisms, such as bacteria, fungi, mites, and viruses, and they fluctuate depending on the microenvironment defined by anatomical location and physiological function. The balance of interactions between the host and microbiota plays a pivotal role in the orchestration of skin homeostasis; however, the disturbance of the balance due to an alteration in the microbial communities, namely, dysbiosis, leads to various skin disorders. Recent developments in sequencing technology have provided new insights into the structure and function of skin microbial communities. Based on high-throughput sequencing analysis, a growing body of evidence indicates that a new treatment using live bacteria, termed bacteriotherapy, is a feasible therapeutic option for cutaneous diseases caused by dysbiosis. In particular, the administration of specific bacterial strains has been investigated as an exclusionary treatment strategy against pathogens associated with chronic skin disorders, whereas the safety, efficacy, and sustainability of this therapeutic approach using isolated live bacteria need to be further explored. In this review, we summarize our current understanding of the skin microbiota, as well as therapeutic strategies using characterized strains of live bacteria for skin inflammatory diseases. The ecosystem formed by interactions between the host and skin microbial consortium is still largely unexplored; however, advances in our understanding of the function of the skin microbiota at the strain level will lead to the development of new therapeutic methods.

Symbiotic microorganisms: prospects for treating atopic dermatitis

INTRODUCTION

Atopic dermatitis (AD) is a common chronic recurrent inflammatory skin disease. The pathogenesis is unclear but may be related to genetic, immune, and environmental factors and abnormal skin barrier function. Symbiotic microorganisms in the gut and on the skin are associated with AD occurrence.

AREAS COVERED

We discuss the metabolism and distribution of intestinal and skin flora and review their relationship with AD, summarizing the recent applications of intestinal and skin flora in AD treatment, and discussing the prospect of research on these two human microbiota systems and their influence on AD treatment. The PubMed database was searched to identify relevant publications from 1949 to 2020 for the bibliometric analysis of atopic dermatitis and symbiotic microorganisms.

EXPERT OPINION

Many studies have suggested a potential contribution of microbes in the intestine and on the skin to AD. Bacteria living on the skin can aggravate AD by secreting numerous virulence factors. Moreover, the metabolism of intestinal flora can influence AD occurrence and development via the circulatory system. Current evidence suggests that by regulating intestinal and skin flora, AD can be treated and prevented.

Antimicrobial Peptide Expression at the Ocular Surface and Their Therapeutic Use in the Treatment of Microbial Keratitis

Microbial keratitis is a common cause of ocular pain and visual impairment worldwide. The ocular surface has a relatively paucicellular microbial community, mostly found in the conjunctiva, while the cornea would be considered relatively sterile. However, in patients with microbial keratitis, the cornea can be infected with multiple pathogens including Staphylococcus aureus, Pseudomonas aeruginosa, and Fusarium sp. Treatment with topical antimicrobials serves as the standard of care for microbial keratitis, however, due to high rates of pathogen resistance to current antimicrobial medications, alternative therapeutic strategies must be developed. Multiple studies have characterized the expression and activity of antimicrobial peptides (AMPs), endogenous peptides with key antimicrobial and wound healing properties, on the ocular surface. Recent studies and clinical trials provide promise for the use of AMPs as therapeutic agents. This article reviews the repertoire of AMPs expressed at the ocular surface, how expression of these AMPs can be modulated, and the potential for harnessing the AMPs as potential therapeutics for patients with microbial keratitis.

Intestinal inflammation alters the antigen-specific immune response to a skin commensal

Resident microbes in skin and gut predominantly impact local immune cell function during homeostasis. However, colitis-associated neutrophilic skin disorders suggest possible breakdown of this compartmentalization with disease. Using a model wherein neonatal skin colonization by Staphylococcus epidermidis facilitates generation of commensal-specific tolerance and CD4⁺ regulatory T cells (Tregs), we ask whether this response is perturbed by gut inflammation. Chemically induced colitis is accompanied by intestinal expansion of S. epidermidis and reduces gut-draining lymph node (dLN) commensal-specific Tregs. It also results in reduced commensal-specific Tregs in skin and skin-dLNs and increased skin neutrophils. Increased CD4⁺ circulation between gut and skin dLN suggests that the altered cutaneous response is initiated in the colon, and resistance to colitis-induced effects in Cd4^creIl1r1^fl/fl mice implicate interleukin (IL)-1 in mediating the altered commensal-specific response. These findings provide mechanistic insight into observed connections between inflammatory skin and intestinal diseases.

Microbiota and maintenance of skin barrier function

Human skin forms a protective barrier against the external environment and is our first line of defense against toxic, solar, and pathogenic insults. Our skin also defines our outward appearance, protects our internal tissues and organs, acts as a sensory interface, and prevents dehydration. Crucial to the skin's barrier function is the colonizing microbiota, which provides protection against pathogens, tunes immune responses, and fortifies the epithelium. Here we highlight recent advances in our understanding of how the microbiota mediates multiple facets of skin barrier function. We discuss recent insights into pathological host-microbiota interactions and implications for disorders of the skin and distant organs. Finally, we examine how microbiota-based mechanisms can be targeted to prevent or manage skin disorders and impaired wound healing.

Early life host-microbe interactions in skin

Our skin is the interface through which we mediate lifelong interactions with our surrounding environment. Initial development of the skin's epidermis, adnexal structures, and barrier function is necessary for normal cutaneous microbial colonization, immune development, and prevention of disease. Early life microbial exposures can have unique and long-lasting impacts on skin health. The identity of neonatal skin microbes and the context in which they are first encountered, i.e., through a compromised skin barrier or in conjunction with cutaneous inflammation, can have additional short- and long-term health consequences. Here, we discuss key attributes of infant skin and endogenous and exogenous factors that shape its relationship to the early life cutaneous microbiome, with a focus on their clinical implications.

Glycerol fermentation by skin bacteria generates lactic acid and upregulates the expression levels of genes associated with the skin barrier function

Commensal bacteria play a major role in multiple skin functions by providing the first layer of defense against pathogens and maintaining the skin barrier. Staphylococcus epidermidis is one of the most common skin commensals. In this study, we showed that S. epidermidis ferments glycerol and uses it as a nutrient, while producing short-chain and organic fatty acids, with the most notable being lactic acid. Lactic acid is an alpha-hydroxy acid that inhibits the growth of pathogenic bacteria, without any negative effect on the commensal bacteria itself. Using in vivo experiments, we validated our in vitro results, showing that the skin microbiome is also capable of doing this. Finally, using 2D and 3D skin culture models, we showed that the fermentation of glycerol, mainly lactic acid, as determined by analytical methods, upregulates the expression levels of several key genes that are associated with the barrier properties of the skin. While the hydration effect of glycerol on the skin is well known, our study shows the overall benefits of glycerol on the skin microbiome, while revealing an alternate mode of action of glycerol for multiple skin benefits.

Type 2 Inflammation Contributes to Skin Barrier Dysfunction in Atopic Dermatitis

Skin barrier dysfunction, a defining feature of atopic dermatitis (AD), arises from multiple interacting systems. In AD, skin inflammation is caused by host-environment interactions involving keratinocytes as well as tissue-resident immune cells such as type 2 innate lymphoid cells, basophils, mast cells, and T helper type 2 cells, which produce type 2 cytokines, including IL-4, IL-5, IL-13, and IL-31. Type 2 inflammation broadly impacts the expression of genes relevant for barrier function, such as intracellular structural proteins, extracellular lipids, and junctional proteins, and enhances Staphylococcus aureus skin colonization. Systemic anti‒type 2 inflammation therapies may improve dysfunctional skin barrier in AD.

Microbiota in health and diseases

The role of microbiota in health and diseases is being highlighted by numerous studies since its discovery. Depending on the localized regions, microbiota can be classified into gut, oral, respiratory, and skin microbiota. The microbial communities are in symbiosis with the host, contributing to homeostasis and regulating immune function. However, microbiota dysbiosis can lead to dysregulation of bodily functions and diseases including cardiovascular diseases (CVDs), cancers, respiratory diseases, etc. In this review, we discuss the current knowledge of how microbiota links to host health or pathogenesis. We first summarize the research of microbiota in healthy conditions, including the gut-brain axis, colonization resistance and immune modulation. Then, we highlight the pathogenesis of microbiota dysbiosis in disease development and progression, primarily associated with dysregulation of community composition, modulation of host immune response, and induction of chronic inflammation. Finally, we introduce the clinical approaches that utilize microbiota for disease treatment, such as microbiota modulation and fecal microbial transplantation.

Skin immunity: dissecting the complex biology of our body's outer barrier

Our skin contributes critically to health via its role as a barrier tissue, carefully regulating passage of key substrates while also providing defense against exogenous threats. Immunological processes are integral to almost every skin function and paramount to our ability to live symbiotically with skin commensal microbes and other environmental stimuli. While many parallels can be drawn to immunobiology at other mucosal sites, skin immunity demonstrates unique features that relate to its distinct topography, chemical composition and microbial ecology. Here we provide an overview of skin as an immune organ, with reference to the broader context of mucosal immunology. We review paradigms of innate as well as adaptive immune function and highlight how skin-specific structures such as hair follicles and sebaceous glands interact and contribute to these processes. Finally, we highlight for the mucosal immunology community a few emerging areas of interest for the skin immunity field moving forward.

Alteration of barrier properties, stratum corneum ceramides and microbiome composition in response to lotion application on cosmetic dry skin

Xerosis, commonly referred to as dry skin, is a common dermatological condition affecting almost a third of the population. Successful treatment of the condition traditionally involves the application of cosmetic products facilitating the moisturisation of the skin with a range of ingredients including glycerol and fatty acids. While the effectiveness of these treatments is not in question, limited information exists on the impact on the skin microbiome following use of these products and the improvement in skin hydration. Here, we describe improvements in skin barrier properties together with increased levels of cholesterol, ceramides and long-chain fatty acids following application of Body Lotion. Concomitant alterations in the skin microbiome are also seen via 16S rRNA metataxonomics, in combination with both traditional and novel informatics analysis. Following 5 weeks of lotion use, beneficial skin bacteria are increased, with improvements in microbiome functional potential, and increases in pathways associated with biosynthesis of multiple long chain fatty acids.

Neuro-immune communication regulating pruritus in atopic dermatitis

Atopic dermatitis (AD) is a common, chronic-relapsing inflammatory skin disease with significant disease burden. Genetic and environmental trigger factors contribute to AD, activating two of our largest organs, the nervous and immune system. Dysregulation of neuro-immune circuits plays a key role in the pathophysiology of AD causing inflammation, pruritus, pain, and barrier dysfunction. Sensory nerves can be activated by environmental or endogenous trigger factors transmitting itch stimuli to the brain. Upon stimulation, sensory nerve endings also release neuromediators into the skin contributing again to inflammation, barrier dysfunction and itch. Additionally, dysfunctional peripheral and central neuronal structures contribute to neuroinflammation, sensitization, nerve elongation, neuropathic itch, thus chronification and therapy-resistance. Consequently, neuro-immune circuits in skin and central nervous system may be targets to treat pruritus in AD. Cytokines, chemokines, proteases, lipids, opioids, ions excite/sensitize sensory nerve endings not only induce itch but further aggravate/perpetuate inflammation, skin barrier disruption, and pruritus. Thus, targeted therapies for neuro-immune circuits as well as pathway inhibitors (e.g., kinase inhibitors) may be beneficial to control pruritus in AD either in systemic and/or topical form. Understanding neuro-immune circuits and neuronal signaling will optimize our approach to control all pathological mechanisms in AD, inflammation, barrier dysfunction and pruritus.

Microbiome function predicts amphibian chytridiomycosis disease dynamics

BACKGROUND

The fungal pathogen Batrachochytrium dendrobatidis (Bd) threatens amphibian biodiversity and ecosystem stability worldwide. Amphibian skin microbial community structure has been linked to the clinical outcome of Bd infections, yet its overall functional importance is poorly understood.

METHODS

Microbiome taxonomic and functional profiles were assessed using high-throughput bacterial 16S rRNA and fungal ITS2 gene sequencing, bacterial shotgun metagenomics and skin mucosal metabolomics. We sampled 56 wild midwife toads (Alytes obstetricans) from montane populations exhibiting Bd epizootic or enzootic disease dynamics. In addition, to assess whether disease-specific microbiome profiles were linked to microbe-mediated protection or Bd-induced perturbation, we performed a laboratory Bd challenge experiment whereby 40 young adult A. obstetricans were exposed to Bd or a control sham infection. We measured temporal changes in the microbiome as well as functional profiles of Bd-exposed and control animals at peak infection.

RESULTS

Microbiome community structure and function differed in wild populations based on infection history and in experimental control versus Bd-exposed animals. Bd exposure in the laboratory resulted in dynamic changes in microbiome community structure and functional differences, with infection clearance in all but one infected animal. Sphingobacterium, Stenotrophomonas and an unclassified Commamonadaceae were associated with wild epizootic dynamics and also had reduced abundance in laboratory Bd-exposed animals that cleared infection, indicating a negative association with Bd resistance. This was further supported by microbe-metabolite integration which identified functionally relevant taxa driving disease outcome, of which Sphingobacterium and Bd were most influential in wild epizootic dynamics. The strong correlation between microbial taxonomic community composition and skin metabolome in the laboratory and field is inconsistent with microbial functional redundancy, indicating that differences in microbial taxonomy drive functional variation. Shotgun metagenomic analyses support these findings, with similar disease-associated patterns in beta diversity. Analysis of differentially abundant bacterial genes and pathways indicated that bacterial environmental sensing and Bd resource competition are likely to be important in driving infection outcomes.

CONCLUSIONS

Bd infection drives altered microbiome taxonomic and functional profiles across laboratory and field environments. Our application of multi-omics analyses in experimental and field settings robustly predicts Bd disease dynamics and identifies novel candidate biomarkers of infection. Video Abstract.

Unravelling the role of surface modification in the dermocompatibility of silver nanoparticles in vitro and in vivo

A clearer picture of interactions between differently coated silver nanoparticles (AgNPs) and biological interfaces that are confronted with by the dermal exposure route is of utmost importance for the risk assessment of various AgNPs-based formulations utilized in the medical and dermocosmetic fields. This work sought to understand how surface modification of AgNPs, especially those produced by green synthesis strategy, affects the surface chemistry and dermocompatibility. Phytosynthetized AgNPs diverse in bio-reducing/capping agents i.e. chlorogenic acid, glycyrrhizic acid and gallic acid, were prepared by a bioinspired green approach and characterized in terms of size, shape, crystal phase, surface charge, structure and antioxidant activity. Chemically synthetized AgNPs stabilized by trisodium citrate or polyvinylpyrrolidone were also analyzed for comparison. The biological test results illustrate that varying coating material for AgNP stabilization results in differential toxicity against dermal microbes and HaCaT keratinocytes in vitro and affects dermal absorption through intact/compromised skin in vivo. Among all test samples, the citrate-stabilized AgNPs displayed the maximum cytotoxicity and dermal absorption. It is also of interest to note that the phytosynthetized AgNPs with chlorogenic acid exhibited superior antioxidant activity, attenuated cytotoxicity and minimal skin deposition, while those modified with glycyrrhizic acid demonstrated a preferentially antibacterial activity against the pathogenic (Escherichia coli and Staphylococcus aureus) over the beneficial strains (Staphylococcus epidermidis) inhabiting human skin. Furthermore, percutaneous absorption of AgNPs into live epidermis was observed on all 7-13 nm sized AgNPs, irrespective of surface coating, with more pronounced skin deposition of silver species occurring for the chemically-synthetized AgNPs within compromised skin. Given all these results, it is concluded that surface modification with particular phytochemicals may render AgNPs with enhanced dermocompatibility or antimicrobial activity. This study provides a basis for risk assessments of phytosynthetized AgNPs in consumer products and suggests the possibility of tailoring AgNPs applicability via green chemistry approach.

Staphylococcus epidermidis Controls Opportunistic Pathogens in the Nose, Could It Help to Regulate SARS-CoV-2 (COVID-19) Infection?

Staphylococcus epidermidis is more abundant in the anterior nares than internal parts of the nose, but its relative abundance changes along with age; it is more abundant in adolescents than in children and adults. Various studies have shown that S. epidermidis is the guardian of the nasal cavity because it prevents the colonization and infection of respiratory pathogens (bacteria and viruses) through the secretion of antimicrobial molecules and inhibitors of biofilm formation, occupying the space of the membrane mucosa and through the stimulation of the host’s innate and adaptive immunity. There is a strong relationship between the low number of S. epidermidis in the nasal cavity and the increased risk of serious respiratory infections. The direct application of S. epidermidis into the nasal cavity could be an effective therapeutic strategy to prevent respiratory infections and to restore nasal cavity homeostasis. This review shows the mechanisms that S. epidermidis uses to eliminate respiratory pathogens from the nasal cavity, also S. epidermidis is proposed to be used as a probiotic to prevent the development of COVID-19 because S. epidermidis induces the production of interferon type I and III and decreases the expression of the entry receptors of SARS-CoV-2 (ACE2 and TMPRSS2) in the nasal epithelial cells.

Inflammatory Response Against Staphylococcus aureus via Intracellular Sensing of Nucleic Acids in Keratinocytes

Staphylococcus aureus is one of the clinically most relevant pathogens causing infections. Humans are often exposed to S. aureus. In approximately one-third of the healthy population it can be found on the skin either for long or short periods as colonizing "commensals", without inducing infections or an inflammatory immune response. While tolerating S. aureus seems to be limited to certain individuals and time periods in most cases, Staphylococcus epidermidis is tolerated permanently on the skin of almost all individuals without activating overwhelming skin inflammation. To investigate this, we co-cultured a keratinocyte cell line (HaCaT) with viable S. aureus or S. epidermidis to study the differences in the immune activation. S. aureus activated keratinocytes depicted by a profound IL-6 and IL-8 response, whereas S. epidermidis did not. Our data indicate that internalization of S. aureus and the subsequent intracellular sensing of bacterial nucleic acid may be essential for initiating inflammatory response in keratinocytes. Internalized dsRNA activates IL-6 and IL-8 release, but not TNF-α or IFNs by human keratinocytes. This is a non-specific effect of dsRNA, which can be induced using Poly(I:C), as well as RNA from S. aureus and S. epidermidis. However, only viable S. aureus were able to induce this response as these bacteria and not S. epidermidis were actively internalized by HaCaT. The stimulatory effect of S. aureus seems to be independent of the TLR3, -7 and -8 pathways.