Commensal Staphylococcus epidermidis contributes to skin barrier homeostasis by generating protective ceramides

Optimizing Skin Surface Metabolomics: A Comprehensive Evaluation of Sampling Methods, Extraction Solvents, and Analytical Techniques

Characterizing the metabolite fingerprint from the skin surface provides invaluable insights into skin biology and microbe-host interactions. To ensure data accuracy and reproducibility, it is essential to develop standard operating procedures for skin surface metabolomics. However, there is a notable lack of studies in this area. In this study, we thoroughly evaluated different sampling materials, extraction solvents, taping methods (frequency and number of tapes), and analytical techniques to optimize skin surface metabolomics. Our results showed that the combination of D-Squame D100 tape with a methyl tert-butyl ether/methanol extractant is optimal for skin surface lipidomics. Performing the skin-taping procedure 5 times with 1 tape yields sufficient biomass for lipid analysis, whereas the optimal taping procedure varies for water-soluble compounds. In addition, our study identified associations among the skin surface metabolites, some of which potentially underlie the formation of microbial cutotypes and offer insights into host-microbe interactions.

Microbe-Host Interaction in Rosacea and its Modulation Through Topical Ivermectin

Rosacea is characterized by inflammatory lesions, often accompanied by an increased density of the common skin mite Demodex folliculorum. Although rosacea shows a high prevalence and significantly affects the quality of life of patients, the underlying mechanisms, especially the role of cutaneous dysbiosis are largely unknown. Hence, we aimed to systematically characterize disease severity of rosacea patients in the context of mite density, the cutaneous microbiome and the host's transcriptome before and after 30 days of topical 1% ivermectin cream treatment. At day 30, a marked decrease in mite density was observed in 87.5% of patients. At day 0, distinct microbial community changes included the decrease in Cutibacterium acnes abundance, while Staphylococcus epidermidis colonization increased when compared to healthy volunteers. Interestingly, the insect symbiont Snodgrassella alvi was recovered from a highly Demodex-colonized patient and eradicated by day 30 of treatment. Although topical ivermectin did not affect bacterial dysbiosis, the host's transcriptome significantly normalized and an "ivermectin transcriptomic signature" was defined. Findings of the present study support that rosacea lesions are associated with dysbiosis. However, improvement of clinical signs during topical ivermectin is not associated with normalization of the bacterial microbiome, but rather a decrease of transcriptomic dysregulation and mite density.

Lactobacillus-derived artificial extracellular vesicles for skin rejuvenation and prevention of photo-aging

Extracellular vesicles (EVs) are small membrane-bound sacs released by cells that play crucial roles in intercellular communication. They transport biomolecules between cells and have both diagnostic and therapeutic potential. Artificial EVs, designed to mimic natural EVs, have been developed using various methods. In this study, Lactobacillus plantarum was used to create Lactobacillus-derived artificial EVs (LAEs) for skin rejuvenation and anti-aging. LAEs demonstrated monodispersity and effectively improved adverse gene expression and wound healing in fibroblasts. They also modulated aging-related genes and improved skin conditions in humans. Their simplicity, promptness, and lack of animal-derived sources make LAEs a promising alternative to natural EVs. LAEs have the potential to overcome the technical limitations of artificial EVs and advance EVs or exosome-based technologies for comprehensive skin rejuvenation.

Investigating the Effect of Enzymatically-Derived Blackcurrant Extract on Skin Staphylococci Using an In Vitro Human Stratum Corneum Model

Background/Objectives: Numerous intrinsic and extrinsic stressors can disrupt the balance of the skin microbiome, leading to the development of various skin diseases. It has been proven that coagulase-negative staphylococci (CoNS) are important commensals for maintaining skin microbiome homeostasis and fighting cutaneous pathogens such as Staphylococcus aureus (S. aureus). Here, we examined the influence of polyphenol-rich enzymatic blackcurrant extract (EBCE) on pathogenic coagulase-positive S. aureus strains and beneficial CoNS, like Staphylococcus epidermidis (S. epidermidis), to explore its potential for rebalancing the skin microbiota. Methods: The polyphenol profile of EBCE was determined by ultra-high-pressure liquid chromatography-tandem mass spectrometry. Microwell plate assays were employed to study the effect of EBCE on five S. aureus strains isolated from the skin of atopic dermatitis patients. An in vitro human stratum corneum model was used to test its effect on mixed bacterial cultures. Results: EBCE inhibited the growth of all tested S. aureus strains by 80-100% at the highest tested concentration after 7 h. No microbial growth was observed at the highest tested EBCE concentration using the stratum corneum model inoculated with one selected pathogen (S. aureus SA-DUS-017) and one commensal laboratory strain (S. epidermidis DSM 20044). The lowest tested concentration did not interfere with S. aureus growth but strongly stimulated the growth of S. epidermidis (~300-fold colony forming unit increase). In addition, low EBCE concentrations strongly stimulated CoNS growth in microbiome samples taken from the armpits of healthy volunteers that were spiked with S. aureus SA-DUS-017. Conclusions: These preclinical data support further testing of EBCE-enriched topical preparations as potential cutaneous prebiotics in human studies.

Disrupting the balance: how acne duration impacts skin microbiota assembly processes

Growing interest in the impact of microbial balance on health has driven studies on the ecological processes shaping the skin microbiota. Skin diseases, which alter the skin's local environment, can disrupt the microbial structure and interact with the disease itself. However, research on microbial assembly in diseased skin remains limited. In this study, we applied ecological models to characterize the processes shaping the skin microbiota in acne patients, considering the impact of disease duration on both skin pores and surfaces using bacterial amplicon sequencing. Our results revealed a significant shift in microbial diversity on the skin surface of patients with long-term acne. Further microbial community analyses showed a transition in ecological processes from healthy to diseased skin. Microbial communities on the skin surfaces of healthy controls and individuals with short-duration acne were primarily driven by heterogeneous selection, whereas microbial drift dominated the assembly process in the long-duration groups. Using the Sloan neutral model, we classified amplicon sequence variants (ASVs) into high-effect and low-effect groups based on relative abundance and sample occurrence. High-effect ASVs, likely exerting a greater ecological influence, were predominantly represented by Cutibacterium across all acne-affected skin groups, while Staphylococcus became enriched among high-effect ASVs in patients with long-term acne. Functional profiling further demonstrated that high-effect ASVs were significantly enriched in motility-related pathways. Additionally, we observed a reduction in microbial network complexity on skin surfaces as disease duration increased. Overall, the ecological dynamics of skin microbial communities may offer valuable insights into the mechanisms underlying disease onset and persistence.IMPORTANCEThe skin microbiota plays a critical role in acne development, yet the processes governing microbial assembly during acne progression remain poorly understood. Previous studies predominantly focused on factors such as acne severity, location, and duration in relation to skin microbial structure, with little attention given to the ecological mechanisms shaping the communities. In this study, we applied ecological models to investigate the processes influencing microbial assembly of skin microbiota in acne patients with varying disease durations and examined functions of ecologically important non-neutral amplicon sequence variants (ASVs). Our findings reveal a transition in ecological processes from deterministic to neutral processes as acne duration increased, with non-neutral ASVs potentially contributing to acne pathogenicity and persistence. These insights contribute to a deeper understanding of the ecological dynamics underlying acne and indicate that targeting these non-neutral ASVs or their associated functions may serve as the basis for future therapeutic strategies.

Barrier Integrity and Immunity: Exploring the Cutaneous Front Line in Health and Disease

Immune responses are influenced by not only immune cells but also the tissue microenvironment where these cells reside. Recent advancements in understanding the underlying molecular mechanisms and structures of the epidermal tight junctions (TJs) and stratum corneum (SC) have significantly enhanced our knowledge of skin barrier functions. TJs, located in the granular layer of the epidermis, are crucial boundary elements in the differentiation process, particularly in the transition from living cells to dead cells. The SC forms from dead keratinocytes via corneoptosis and features three distinct pH zones critical for barrier function and homeostasis. Additionally, the SC-skin microbiota interactions are crucial for modulating immune responses and protecting against pathogens. In this review, we explore how these components contribute both to healthy and disease states. By targeting the skin barrier in therapeutic strategies, we can enhance its integrity, modulate immune responses, and ultimately improve outcomes for patients with inflammatory skin conditions.

Conversation between skin microbiota and the host: from early life to adulthood

Host life is inextricably linked to commensal microbiota, which play a crucial role in maintaining homeostasis and immune activation. A diverse array of commensal microbiota on the skin interacts with the host, influencing the skin physiology in various ways. Early-life exposure to commensal microbiota has long-lasting effects, and disruption of the epidermal barrier or transient exposure to these microorganisms can lead to skin dysbiosis and inflammation. Several commensal skin microbiota have the potential to function as either commensals or pathogens, both influencing and being influenced by the pathogenesis of skin inflammatory diseases. Here we explore the impact of various commensal skin microbiota on the host and elucidate the interactions between skin microbiota and host systems. A deeper understanding of these interactions may open new avenues for developing effective strategies to address skin diseases.

Prurigo nodularis and the microbiome

Prurigo nodularis (PN) is a chronic skin condition that profoundly impacts quality of life. Histopathological studies of itchy hyperkeratotic nodules show dense infiltrates of T lymphocytes, mast cells, and eosinophils. A robust inflammatory response is implicated, coupled with key changes in neuronal plasticity that affect nerve fiber architecture and function. The microbial community in PN lesions exhibits a distinct composition, marked by decreased α-diversity and a prominent increase in Staphylococcus aureus (S aureus). This alteration appears to contribute to the disease's pathophysiology, causing further disruption of the skin barrier, immune dysregulation, and neuronal plasticity. There is ample evidence that virulence factors of S aureus promote Th2, Th17, and Th22 cytokine production, which are key to PN. In addition, S aureus V8 protease (Endoproteinase Glu-C) has recently been identified to trigger robust itch by activating protease-activated receptor 1 (PAR1) on sensory neurons. This review underscores the complex interplay between the altered microbiome and the itch-scratch cycle of PN, providing insights into potential therapeutics targeting the skin microbiome. A multidisciplinary approach is crucial for providing relief to individuals suffering from this skin condition.

Multi-perspective analysis of skin microbiota in elderly eczema patients

Eczema is a common inflammatory skin disease in elderly people. It not only causes physical damage to elderly people but also seriously affects their mental health. The skin microbiota plays a vital role in the development of skin disease. However, relatively few studies have investigated the characteristics of the skin microbiota in elderly eczema patients. In this study, the differences in the composition of the skin microbiota between lesion sites and healthy sites, between exposed sites and unexposed sites, and between elderly and younger eczema sites were analyzed, aiming to characterize the skin microbiota in elderly eczema patients from multiple perspectives and provide a basis for clinical diagnosis and treatment. The results indicated that the species richness of elderly eczema patients was greater than that of younger eczema patients. There was no significant difference between groups at the phylum level. At the genus level, the abundance of Staphylococcus significantly increased in the lesion sites of the elderly group. Compared with the younger eczema group, the elderly eczema group had greater abundances of Paracoccus, Deinococcus_B, Kaistella, Escherichia_710834, and Chryseobacterium_796703. These findings indicated that more attention should be given to the roles of Kaistella and Streptococcus in elderly eczema patients because Kaistella was the only genus among the 20 most abundant genera that was closely related to the EASI scores. Moreover, correlation analysis suggested that many genera had a positive relationship with Streptococcus. The results provide basic microbiological data for physicians treating elderly patients with eczema.

Pinosylvin: A Multifunctional Stilbenoid with Antimicrobial, Antioxidant, and Anti-Inflammatory Potential

Stilbenoids are a category of plant compounds exhibiting notable health-related benefits. After resveratrol, perhaps the most well-known stilbenoid is pinosylvin, a major phytochemical constituent of most plants characterised by the pine spines among others. Pinosylvin and its derivatives have been found to exert potent antibacterial and antifungal effects, while their antiparasitic and antiviral properties are still a subject of ongoing research. The antioxidant properties of pinosylvin are mostly based on its scavenging of free radicals, inhibition of iNOS and protein kinase C, and promotion of HO-1 expression. Its anti-inflammatory properties are based on a variety of mechanisms, such as COX-2 inhibition, NF-κB and TRPA1 activation inhibition, and reduction in IL-6 levels. Its anticancer properties are partly associated with its antioxidant and anti-inflammatory potential, although a number of other mechanisms are described, such as apoptosis induction and matrix metalloproteinase inhibition. A couple of experiments have also suggested a neuroprotective potential. A multitude of ethnomedical and ethnobotanical effects of pinosylvin-containing plants are reported, like antimicrobial, antioxidant, anti-inflammatory, hepatoprotective, and prokinetic actions; many of these are corroborated by recent research. The advent of novel methods of artificial pinosylvin synthesis may facilitate its mass production and adoption as a medical compound. Finally, pinosylvin may be a tool in promoting environmentally friendly pesticide and insecticide policies and be used in land remediation schemes.

Research hotspots and trends of skin barrier in atopic dermatitis in the past 24-year: a bibliometric analysis

Background

Atopic dermatitis (AD) is a chronic, pruritic, inflammatory skin condition that imposes significant psychological and economic burdens on patients due to its recurring nature. Its etiology is multifactorial, involving interactions between genetic predispositions and environmental factors. The skin barrier serves as both a mechanical and immunological defense, and its structural damage and functional impairments significantly contribute to the pathogenesis of AD. This study aims to explore the future prospects and developmental trends of the skin barrier in the context of AD through a bibliometric analysis.

Objective

To analyze the research status, hot spots and development trend of skin barrier in AD.

Methods

Relevant studies were extracted from the Web of Science database and screened by researchers, with bibliometric analysis conducted using VOSviewer, CiteSpace, and other tools.

Results

A total of 4,227 publications were identified over a 24-year research period. The United States is the leading contributor, with 1,263 publications, and demonstrates extensive collaboration with numerous countries. The journal with the highest number of publications is the Journal of Allergy and Clinical Immunology. The most prolific institutions is the University of California, San Francisco. Recent years have seen high citation intensity for keywords such as "dupilumab," "barrier dysfunction," and "gut microbiota".

Conclusion

The mechanism of the skin barrier in AD remains an area requiring ongoing research and analysis. Although significant progress has been achieved, future research will benefit from advancements in technology.

Melatonin treatment increases skin microbiota-derived propionic acid to alleviate atopic dermatitis

BACKGROUND

Melatonin has been reported to relieve the inflammatory symptoms and improve sleep disturbance in patients with atopic dermatitis (AD). Recent studies showed that melatonin produced beneficial effects by remodeling intestinal microbiota composition; however, whether the beneficial effects of melatonin in AD were mediated by the modulation of skin microbiota remains unclear.

OBJECTIVE

We sought to investigate the mechanism by which melatonin treatment-induced changes in the skin microbiota composition further alleviated AD.

METHODS

The changes in skin bacterial composition after melatonin treatment were detected by 16S-rRNA sequencing. Further mechanisms were explored in calcipotriol (MC903)-induced AD mice and HaCaT cells through skin microbiota transplantation, quantification detection of short-chain fatty acids, transcriptome and single-cell sequencing analysis, quantitative RT-PCR, Western blotting, and Cell Counting Kit-8 assay.

RESULTS

We demonstrated that melatonin reshaped the skin microbiota in AD mice. The transplantation of skin microbiota from melatonin-treated mice alleviated AD symptoms in mice. Skin microbiota-derived short-chain fatty acids, especially propionic acid, were increased in the skin of melatonin-treated AD mice, which further inhibited FABP5 expression to alleviate AD. Propionic acid also inhibited FABP5 expression in HaCaT cells, which was reversed by the treatment of GPR43 inhibitor GLPG0974. GLPG0974 also blocked the therapeutic effects of melatonin on AD mice.

CONCLUSIONS

Our study demonstrated that melatonin alleviates AD through the skin microbiota/propionic acid/GPR43/FABP5 axis, highlighting a novel role of melatonin as a modulator of skin microbiota to alleviate AD.

Skin Microbiome Dynamics in Atopic Dermatitis: Understanding Host-Microbiome Interactions

Atopic dermatitis (AD) is a chronic inflammatory skin disorder affecting both children and adults, characterized by pruritus, eczematous lesions, and compromised skin barrier function. A key feature of AD is dysbiosis of the skin microbiome, marked by reduced microbial diversity and the overgrowth of Staphylococcus aureus in lesional skin. S. aureus exacerbates skin barrier dysfunction and immune dysregulation, leading to recurrent infections and disease flares. In contrast, commensal bacteria such as Staphylococcus epidermidis and Roseomonas mucosa may exert protective effects by inhibiting S. aureus colonization and modulating immune responses. Beyond microbial composition, microbial metabolites play a crucial role in AD pathophysiology. Short-chain fatty acids, indole derivatives, and other bacterial metabolites influence cutaneous immune responses, lipid metabolism, and skin barrier integrity. Altered metabolite profiles, including reduced levels of beneficial microbial metabolites, are associated with AD severity and disease progression. Notably, S. aureus overabundance correlates with disruption in lipid metabolism, further compromising the skin barrier. This review explores recent advances in understanding the relationship between microbial metabolites and AD pathogenesis and examines the therapeutic potential of microbiome-targeted interventions. Strategies such as probiotics, prebiotics, and topical microbiome transplantation aim to restore microbial diversity and rebalance metabolite production, ultimately improving clinical outcomes in AD patients. Future therapeutic approaches focusing on commensal-derived metabolites offer promising avenues for alleviating symptoms and modulating disease severity in AD.

Do Melanocytes Have a Role in Controlling Epidermal Bacterial Colonisation and the Skin Microbiome?

In addition to producing melanin to protect epidermal keratinocytes against DNA damage, melanocytes may have important roles in strengthening innate immunity against pathogens. We have developed a functional, pigmented, human full-thickness 3D skin equivalent to determine whether the presence of melanocytes impacts epidermal bacterial growth and regulates the expression of genes involved in the immune response. We introduced primary epidermal melanocytes to construct a 3-cell full-thickness skin equivalent with primary dermal fibroblasts and epidermal keratinocytes. Immunohistochemistry verified the appropriate ratio and spatial organisation of melanocytes. Alpha-MSH induced melanogenesis, confirming an appropriate physiological response. We compared this 3-cell skin equivalent with the 2-cell version without melanocytes in response to inoculation with 3 species of bacteria: Staphylococcus epidermidis, Corynebacterium striatum, and Cutibacterium acnes. There was a significant decrease in the colonisation of bacteria in the skin equivalents containing functional melanocytes. There was increased expression of immune-response genes (S100A9, DEFB4A, IL-4R) following microorganism exposure; however, there were marked differences between the unpigmented and pigmented skin equivalents. This physiologically relevant human 3D-skin equivalent opens up new avenues for studying complex skin pigmentation disorders, melanoma, and UV damage, as well as the rapidly evolving field of the skin microbiome and the balance between commensal and pathogenic species.

Crosstalk Between the Skin Environment and Microbial Community in Immune-Related Skin Diseases

The skin surface hosts diverse skin microbiota, including bacteria, fungi, and viruses. Intricate interactions between the skin microenvironment and microbial community are crucial for maintaining cutaneous homeostasis. This review explores the bidirectional relationship between the skin ecosystem and its microbiota. The skin microenvironment is shaped by a combination of intrinsic factors, dominated by sweat glands and pilosebaceous units, and external factors, such as UV radiation and personal care products, which create distinct niches that influence microbial colonization patterns across different skin regions. The skin microbiome, in turn, modulates the physical, chemical, immunological, and microbial barriers of the skin. We also discuss the alterations in this crosstalk in various immune-related skin conditions such as atopic dermatitis, psoriasis, rosacea, hidradenitis suppurativa, skin cancer, and aging. Understanding these interactions is vital for developing targeted microbiome-based therapies for various skin disorders. Further researches are needed to deepen insights into the microbial roles and their therapeutic potentials in skin health and disease.

Living Microneedles for Intradermal Delivery of Beneficial Bacteria

The skin, our first line of defense against external threats, combines a physical barrier and a rich microbial community. Disruptions of this community, for example, due to infectious injury, have been linked to a decrease in bacteria diversity and to mild to severe pathological conditions. Although some progress has been made in the field, possibilities/procedures for restoring the skin microbiome are still far from ideal. The objective of this study was to design and evaluate a dissolvable poly(vinyl alcohol)/polyvinylpyrrolidone microneedle (MN) patch containing live Bacillus subtilis. According to the plan, bacteria were distributed equally throughout the patch without compromising the morphology and mechanical properties of the needles. B. subtilis was successfully released from the MNs, reaching a logarithmic growth phase after 5 h. These MNs demonstrated remarkable antibacterial activity against the Gram-positive pathogenic S. pyogenes, S. aureus, and C. acnes, while the empty control MNs showed no such activity. Finally, mice were inserted with a single MN patch loaded with GFP-B. subtilis presented significantly higher total radiance efficiency (TRE) values compared to the empty-MN mice throughout the entire experiment. This concept of incorporating live, secreting bacteria within a supportive MN patch shows great promise as a bacterial delivery system, offering a potential shift from conventional pharmacological approaches to more sustainable and symbiotic therapies.

Skin microbiome and dermatologic disorders

Human skin acts as a physical barrier to prevent the entry of pathogenic microbes while simultaneously providing a home for commensal bacteria and fungi. Microbiome sequencing studies have demonstrated the unappreciated diversity and selectivity of these microbes. Functional studies have demonstrated the impact of specific strains to tune the immune system, sculpt the microbial community, provide colonization resistance, and promote epidermal barrier integrity. Recent studies have integrated the microbiome, immunity, and tissue integrity to understand their interplay in common disorders such as atopic dermatitis. In this Review, we explore microbiome shifts associated with cutaneous disorders with an eye toward how the microbiome can be mined to identify new therapeutic opportunities.

Staphylococcus felis C4 exhibits in vitro antimicrobial activity against methicillin-resistant Staphylococcus pseudintermedius in a novel canine skin explant model

BACKGROUND

Canine superficial pyoderma is a common bacterial skin infection of dogs, generally caused by Staphylococcus pseudintermedius. The C4 strain of Staphylococcus felis was recently discovered to have strong antimicrobial activity against S. pseudintermedius in mice.

OBJECTIVES

We aimed to evaluate in vitro if this antimicrobial activity was maintained using a novel canine skin explant model.

MATERIALS AND METHODS

Punch biopsies (8 mm) of skin from recently euthanised dogs were collected and placed into six-well plates on top of an agarose pedestal.

RESULTS

Histological examination of the skin explants showed an intact dermal-epidermal organisation and a stratum corneum that was successfully colonised by S. pseudintermedius after topical application. The number of colony forming units of S. pseudintermedius showed a 2 log increase after 24 h colonisation, indicating that the explant supported bacterial growth. By contrast, co-treatment with S. felis C4 live bacteria and its sterile protein product significantly reduced the growth of a methicillin-susceptible (ST540, p = 0.0357) and a methicillin-resistant (MR) strain (ST71, p = 0.0143) of S. pseudintermedius. No detectable bacteria were recovered from or visualised on skin 24 h posttreatment with the S. felis C4 sterile protein product.

CONCLUSIONS AND CLINICAL RELEVANCE

Using a novel canine explant model, we demonstrate that the S. felis C4 strain inhibits the growth of S. pseudintermedius and that it is a promising candidate for a new probiotic therapy to treat cutaneous infections caused by S. pseudintermedius, including MR strains.

In vitro analysis of XLAsp-P2 peptide loaded cellulose acetate nanofiber for wound healing

Recently, nanofiber-based wound dressings are currently a viable strategy to expedite the healing of wounds by providing a suitable microenvironment for tissue growth with active ingredients. This research study subjects the development of electrospun cellulose acetate (CA) nanofibers loaded with the XLAsp-P2, an antimicrobial peptide (AMP) that holds great potential for enhanced wound healing as a therapeutic agent. The synthesized XLAsp-P2-loaded CA nanofibers were fabricated via three loading percentages, 0.1 %, 0.2 %, and 0.3 % w/w, and characterized and evaluated their antimicrobial potential with MTT assay and Agar overlay methods as an alternative strategy. FT-IR analysis confirmed the compatibility of the peptide-loaded CA nanocomposite, showing distinct peaks corresponding to the constituent materials. Scanning electron microscopy (SEM) analysis was employed to characterize the morphology of electrospun peptide CA nanocomposites and illustrate the fiber's size at the nanoscale. The in vitro release study during the 24 hr, 87 % of the peptide was released which was approximately 5.2 mg; which was closer matched to the square root model of Higuchi at room temperature. MTT assay presented sensitive results towards Gram-positive bacteria compared to Gram Negative bacteria; which corresponded to the inhibition zones of the Agar overlay method proving that Escherichia coli (ATCC 25922) 17.66 ± 0.38 mm and Pseudomonas aeruginosa (ATCC 27853) 17.44 ± 0.38 mm exhibited moderate susceptibility, while Staphylococcus aureus (ATCC 25923)19.89 ± 0.69 mm and Bacillus cereus (ATCC 11778) 23.00 ± 0.33 mm showed promising responses. Collectively, The study's findings indicate that the XLAsp-P2 incorporated CA mat possesses an opportunity to function as an efficient platform for delivering therapeutic peptides.

The prebiotic effects of fructooligosaccharides enhance the growth characteristics of Staphylococcus epidermidis and enhance the inhibition of Staphylococcus aureus biofilm formation

OBJECTIVE

Oligosaccharides have been shown to enhance the production of short chain fatty acids (SCFAs) by gut probiotics and regulate gut microbiota, to improve intestinal health. Recent research indicates that oligosaccharides may also positively impact skin microbiota by selectively promoting the growth of skin commensal bacteria and inhibiting pathogenic bacteria. However, the specific metabolic and regulatory mechanisms of skin commensal bacteria in response to oligosaccharides remain unclear. This study aims to explore the influence of four oligosaccharides on the growth and metabolism of Staphylococcus epidermidis and further identify skin prebiotics that can enhance its probiotic effects on the skin.

METHODS

Fructooligosaccharides (FOS), isomaltooligosaccharide (IMO), galactooligosaccharides (GOS) and inulin were compared in terms of their impact on cell proliferation, SCFAs production of S. epidermidis CCSM0287 and the biofilm inhibition effect of their fermentation supernatants on Staphylococcus aureus CCSM0424. Furthermore, the effect of FOS on S. epidermidis CCSM0287 was analysed by the transcriptome analysis.

RESULTS

All four oligosaccharides effectively promoted the growth of S. epidermidis CCSM0287 cells, increased the production of SCFAs, with FOS demonstrating the most significant effect. Analysis of the SCFAs indicated that S. epidermidis CCSM0287 predominantly employs oligosaccharides to produce acetic acid and isovaleric acid, differing from the SCFAs produced by gut microbiota. Among the four oligosaccharides, the addition of 2% FOS fermentation supernatant significantly inhibited S. aureus CCSM0424 biofilm formation. Furthermore, RNA sequencing revealed 162 differentially expressed genes (84 upregulated and 78 downregulated) of S. epidermidis CCSM0287 upon FOS treatment compared with glucose treatment. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis highlighted differences in the amino acid synthesis pathway, particularly in terms of arginine biosynthesis.

CONCLUSION

FOS promotes cell proliferation, increases the SCFA production of S. epidermidis CCSM0287 and enhance the inhibition of S. aureus biofilm formation, suggesting that FOS serves as a potential prebiotic for strain S. epidermidis CCSM0287.

Commensal-derived tryptophan metabolites fortify the skin barrier: Insights from a 50-species gnotobiotic model of human skin microbiome

The epidermal barrier defends the body against dehydration and harmful substances. The commensal microbiota is essential for proper differentiation and repair of the epidermal barrier, an effect mediated by the aryl hydrocarbon receptor (AHR). However, the microbial mechanisms of AHR activation in skin are less understood. Tryptophan metabolites are AHR ligands that can be products of microbial metabolism. To identify microbially regulated tryptophan metabolites in vivo, we established a gnotobiotic model colonized with fifty human skin commensals and performed targeted mass spectrometry on murine skin. Indole-related metabolites were enriched in colonized skin compared to germ-free skin. In reconstructed human epidermis and in murine models of atopic-like barrier damage, these metabolites improved barrier repair and function individually and as a cocktail. These results provide a framework for the identification of microbial metabolites that mediate specific host functions, which can guide the development of microbe-based therapies for skin disorders.

Skin microbiota: pathogenic roles and implications in atopic dermatitis

Atopic dermatitis (AD) is a chronic and inflammatory skin disorder characterized by impaired barrier function and imbalanced immunity. Recent advances have revealed that dysbiosis of skin microbiota plays important roles in the pathogenesis and development of AD. Meanwhile, endogenous and external factors contribute to the dysbiosis of skin microbiota in AD. Additionally, various treatments, including topical treatments, phototherapy, and systemic biologics, have demonstrated positive impacts on the clinical outcomes, alongside with the modulations of cutaneous microbiota in AD patients. Importantly, therapeutics or products regulating skin microbiota homeostasis have demonstrated potential for AD treatment in early clinical studies. In this review, we underline changes of the skin microbiota correlated with AD. Meanwhile, we provide an overview of the skin microbiota regarding its roles in the pathogenesis and development of AD. Finally, we summarize therapeutic strategies restoring the skin microbial homeostasis in AD management.

Ribotyping Staphylococcus epidermidis Using Probabilistic Sequence Analysis and Levenshtein Distance Algorithm

Staphylococcus epidermidis (S. epidermidis) live in different human locations and natural environments. For ribotyping S. epidermidis sub-species, 2507 PCR-amplified reads of 16S rRNA genes of S. epidermidis in a public dataset were used for probabilistic sequence analysis. A sequence probability logo (sequence pLogo) as a reference sequence of 16S rRNA genes of S. epidermidis was constructed. Through implementation of Levenshtein Distance algorithm, two 20-base pairs (bp) motifs, commonly present in 2507 PCR-amplified reads, were identified. The top 38 S. epidermidis isolates, which carried 16S rRNA nucleotide domains that were made of different sequences but have high similarity scores to two 20-bp motifs, were found from 11 human, 8 animal, 9 plant and 10 environmental samples, indicating that these two 20-bp motifs were broadly present in diverse S. epidermidis isolates. Thirty-one PCR-amplified reads of 16S rRNA genes, which were currently not in the dataset, were utilized to verify the feasibility of using two 20-bp motifs for ribotyping S. epidermidis sub-species. S. epidermidis S1, S3, but not S2, isolates on the human scalp carried a 20-bp sequence domain with high similarities to a 20-bp motif in the sequence pLogo. The phylogenetic tree showed that S. epidermidis S1, S2 and S3 were not from a single common ancestor. Two newly identified 20-bp motifs here, thus, provided reference nucleotide residues for ribotyping S. epidermidis.

Non-antibiotic approaches to mitigating wound infections: Potential for SSRIs and adrenergic antagonists as emerging therapeutics

Bacterial biofilms represent a formidable challenge in the treatment of chronic wounds, largely because of their resistance to conventional antibiotics. The emergence of multidrug-resistant (MDR) bacterial strains exacerbates this issue, necessitating a shift towards exploring alternative therapeutic approaches. In response to this urgent need, there has been a surge in research efforts aimed at identifying effective non-antibiotic treatments. Recently noted among the non-antibiotic options are selective serotonin reuptake inhibitors (SSRIs) and beta-adrenergic (β-AR) antagonists. Both have demonstrated antimicrobial activities and wound-healing properties, which makes them particularly promising potential therapeutics for chronic wounds. This review seeks to comprehensively evaluate the landscape of non-antibiotic strategies for managing wound infections. By analysing the latest research findings and clinical developments, it aims to shed light on emerging therapeutic alternatives. Additionally, the review delves into the potential of repurposing systemic therapeutics for topical application, offering insights into the feasibility and challenges associated with current approaches. We also address the necessity of translating promising preclinical results into tangible clinical benefits.

Gut bacterial sphingolipid production modulates dysregulated skin lipid homeostasis

Sphingolipids are an essential lipid component of the skin barrier with alterations in skin sphingolipid composition associated with multiple skin disorders including psoriasis, atopic dermatitis, and ichthyosis. Contributions to skin sphingolipid abundance are not well characterized, thus the main method of modulating skin lipid levels is the topical application of creams rich with sphingolipids at the skin surface. Evidence that diet and gut microbiome function can alter skin biology proposes an intriguing potential for the modulation of skin lipid homeostasis through gut microbial metabolism, but potential mechanisms of action are not well understood. Sphingolipid synthesis by prominent gut microbes has been shown to affect intestinal, hepatic and immune functions with the potential for sphingolipid-producing bacteria to affect skin biology through altering skin sphingolipid levels. To address this question, we used bioorthogonal chemistry to label lipids from the sphingolipid-producing bacteria Bacteroides thetaiotaomicron and trace these lipids to the skin epidermis. Exposing mice to B. thetaiotaomicron strains mutant in the ability to produce sphingolipids resulted in significantly lower transfer of gut microbiome-derived lipids to the skin, while also altering skin biology and altering expression of skin barrier genes. Measurement of skin ceramide levels, a class of sphingolipids involved in skin barrier function, determined that skin sphingolipid levels were altered in the presence of gut sphingolipid-producing bacteria. Together this work demonstrates that gut bacterial lipids can transfer to the skin and provides a compelling avenue for modulating sphingolipid-dominant compartments of the skin using sphingolipid-producing bacteria of the gut microbiome.

Unveiling the hidden causal links: skin flora and cutaneous melanoma

Objective

The presence of skin flora (SF) has been identified as a significant factor in the onset and progression of cutaneous melanoma (CM). However, the vast diversity and abundance of SF present challenges to fully understanding the causal relationship between SF and CM.

Methods

A Two Sample Mendelian Randomization (TSMR) analysis was conducted to investigating the causal relationship between SF and CM. The Inverse-Variance Weighted (IVW) method was utilized as the primary approach to assess the causal relationship under investigation. Furthermore, an independent external cohort was employed to validate the initial findings, followed by a meta-analysis of the consolidated results. To address potential confounding factors related to the influence of SF on CM, a Multivariate Mendelian Randomization (MVMR) analysis was also conducted. Finally, a Reverse Mendelian Randomization (RMR) was conducted to further validate the causal association.

Results

TSMR results showed that 9 SF have a causal relationship with CM in the training cohort. Although these 9 SF weren't confirmed in the testing cohort, 4 SF remained significant in the meta-analysis after integrating results from both cohorts. MVMR analysis indicated that 3 SF were still significantly associated with CM after accounting for the interactions between different SF in the training cohort. No reverse causal relationship was identified in RMR analysis.

Conclusion

A total of 9 SF were identified as having a potential causal relationship with CM; however, a large randomized controlled trial is needed to verify these results.

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.

Microenvironmental host-microbe interactions in chronic inflammatory skin diseases

Several microbiome studies have recently demonstrated microbial dysbiosis in various chronic inflammatory skin diseases, and it is considered an important role in the pathogenesis. Although the role of skin dysbiosis in inflammatory skin diseases is debatable, the local microenvironment is considered essential concerning compositional changes and functional alterations of the skin microbiota. Indeed, various local nutrients (e.g., lipids), pH values, water, oxygen, and antimicrobial peptides may affect the level of skin dysbiosis in these skin diseases. In particular, in atopic dermatitis and hidradenitis suppurativa, significant changes in skin dysbiosis have been associated with local aberrant host immune changes. In this review, the potential pathogenic crosstalk between the host and the microbiota is reviewed in relation to the physical, chemical, and biological microenvironments of various chronic inflammatory skin diseases.

A greener side of health care: Revisiting phytomedicine against the human fungal pathogen Malassezia

Malassezia species are commensal fungi residing on the skin and in the gut of humans and animals. Yet, under certain conditions, they become opportunistic pathogens leading to various clinical conditions including dermatological disorders. The emergence of drug resistance and adverse effects associated with conventional antifungal agents has propelled the search for alternative treatments, among which phytomedicine stands out prominently. Phytochemicals, including phenolic acids, flavonoids, and terpenoids, demonstrate potential antifungal activity against Malassezia by inhibiting its growth, adhesion, and biofilm formation. Furthermore, the multifaceted therapeutic properties of phytomedicine (including anti-fungal and, antioxidant properties) contribute to its efficacy in alleviating symptoms associated with Malassezia infections. Despite these promising prospects, several challenges hinder the widespread adoption of phytomedicine in clinical practice mostly since the mechanistic studies and controlled experiments to prove efficacy have not been done. Issues include standardization of herbal extracts, variable bioavailability, and limited clinical evidence. Hence, proper regulatory constraints necessitate comprehensive research endeavors and regulatory frameworks to harness the full therapeutic potential of phytomedicine. In conclusion, while phytomedicine holds immense promise as an alternative or adjunctive therapy against Malassezia, addressing these challenges is imperative to optimize its efficacy and ensure its integration into mainstream medical care. In this review we provide an update on the potential phytomedicines in combating Malassezia-related ailments, emphasizing its diverse chemical constituents and mechanisms of action.

Role of microbiota in the GUT-SKIN AXIS responses to outdoor stressors

Beside the respiratory tract, the skin and the gut represent the first defensive lines of our body against the external insults displaying many important biochemical features able to maintain the epithelial barrier integrity and to regulate the tissue immune responses. The human microbiome is essential in maintaining the tissue homeostasis and its dysregulation may lead to tissue conditions including inflammatory pathologies. Among all external insults, air pollutants have been shown to cause oxidative stress damage within the target tissues via an OxInflammatory response. Dysregulation of the gut microbiome (dysbiosis) by outdoor stressors, including air pollutants, may promote the exacerbation of the skin tissue damage via the interplay between the gut-skin axis. The intent of this review is to highlight the ability of exogenous stressors to modulate the human gut-skin axis via a redox regulated mechanism affecting the microbiome and therefore contributing to the development and aggravation of gut and skin conditions.

Large-scale investigation for antimicrobial activity reveals novel defensive species across the healthy skin microbiome

The human skin microbiome constitutes a dynamic barrier that can impede pathogen invasion by producing antimicrobial natural products. Gene clusters encoding for production of secondary metabolites, biosynthetic gene clusters (BGCs), that are enriched in the human skin microbiome relative to other ecological settings, position this niche as a promising source for new natural product mining. Here, we introduce a new human microbiome isolate collection, the EPithelial Isolate Collection (EPIC). It includes a large phylogenetically diverse set of human skin-derived bacterial strains from eight body sites. This skin collection, consisting of 980 strains is larger and more diverse than existing resources, includes hundreds of rare and low-abundance strains, and hundreds of unique BGCs. Using a large-scale co-culture screen to assess 8,756 pairwise interactions between skin-associated bacteria and potential pathogens, we reveal broad antifungal activity by skin microbiome members. Integrating 287 whole isolate genomes and 268 metagenomes from sampling sites demonstrates that while the distribution of BGC types is stable across body sites, specific gene cluster families (GCFs), each predicted to encode for a distinct secondary metabolite, can substantially vary. Sites that are dry or rarely moist harbor the greatest potential for discovery of novel bioactive metabolites. Among our discoveries are four novel bacterial species, three of which exert significant and broad-spectrum antifungal activity. This comprehensive isolate collection advances our understanding of the skin microbiomes biosynthetic capabilities and pathogen-fighting mechanisms, opening new avenues towards antimicrobial drug discovery and microbiome engineering.

Multi-drug resistant Staphylococcus epidermidis from chronic wounds impair healing in human wound model

Venous leg ulcers (VLUs) represent one of the most prevalent types of chronic wounds characterised by perturbed microbiome and biofilm-forming bacteria. As one of the most abundant skin-commensal, Staphylococcus epidermidis is known as beneficial for the host, however, some strains can form biofilms and hinder wound healing. In this study, S. epidermidis distribution in VLUs and associated resistome were analysed in ulcer tissue from patients. Virulence of S. epidermidis isolates from VLUs were evaluated by whole genome sequencing, antimicrobial susceptibility testing, in vitro biofilm and binding assays, and assessment of biofilm-forming capability and pro-inflammatory potential using human ex vivo wound model. We demonstrated that S. epidermidis isolates from VLUs inhibit re-epithelialization through biofilm-dependent induction of IL-1β, IL-8, and IL-6 which was in accordance with impaired healing outcomes observed in patients. High extracellular matrix binding ability of VLU isolates was associated with antimicrobial resistance and expression levels of the embp and sdrG, responsible for bacterial binding to fibrinogen and fibrin, respectively. Finally, we showed that S. epidermidis from VLUs demonstrate pathogenic features with ability to impair healing which underscores the emergence of treatment-resistant virulent lineages in patients with chronic ulcers.

The Core-Shell Microneedle with Probiotic Extracellular Vesicles for Infected Wound Healing and Microbial Homeostasis Restoration

Wound healing is a dynamic process involving the timely transition of organized phases. However, infected wounds often experience prolonged inflammation due to microbial overload. Thus, addressing the viable treatment needs across different healing stages is a critical challenge in wound management. Herein, a novel core-shell microneedle (CSMN) patch is designed for the sequential delivery of tannic acid-magnesium (TA-Mg) complexes and extracellular vesicles from Lactobacillus druckerii (LDEVs). Upon application to infected sites, CSMN@TA-Mg/LDEV releases TA-Mg first to counteract pathogenic overload and reduce reactive oxygen species (ROS), aiding the transition to proliferative phase. Subsequently, the sustained release of LDEVs enhances the activities of keratinocytes and fibroblasts, promotes vascularization, and modulates the collagen deposition. Notably, dynamic track of microbial composition demonstrates that CSMN@TA-Mg/LDEV can both inhibit the aggressive pathogen and increase the microbial diversity at wound sites. Functional analysis further highlights the potential of CSMN@TA-Mg/LDEV in facilitating wound healing and skin barrier restoration. Moreover, it is confirmed that CSMN@TA-Mg/LDEV can accelerate wound closure and improve post-recovery skin quality in the murine infected wound. Conclusively, this innovative CSMN patch offers a rapid and high-quality alternative treatment for infected wounds and emphasizes the significance of microbial homeostasis.

Commensal Skin Bacteria Exacerbate Inflammation and Delay Skin Barrier Repair

The skin microbiome can both trigger beneficial immune stimulation and pose a potential infection threat. Previous studies have shown that colonization of mouse skin with the model human skin commensal Staphylococcus epidermidis is protective against subsequent excisional wound or pathogen challenge. However, less is known about concurrent skin damage and exposure to commensal microbes, despite growing interest in interventional probiotic therapy. In this study, we address this open question by applying commensal skin bacteria at a high dose to abraded skin. Although depletion of the skin microbiome through antibiotics delayed repair from damage, probiotic-like application of commensals-including the mouse commensal Staphylococcus xylosus, 3 distinct isolates of S. epidermidis, and all other tested human skin commensals-also significantly delayed barrier repair. Increased inflammation was observed within 4 hours of S. epidermidis exposure and persisted through day 4, at which point the skin displayed a chronic wound-like inflammatory state with increased neutrophil infiltration, increased fibroblast activity, and decreased monocyte differentiation. Transcriptomic analysis suggested that the prolonged upregulation of early canonical proliferative pathways inhibited the progression of barrier repair. These results highlight the nuanced role of members of the skin microbiome in modulating barrier integrity and indicate the need for caution in their development as probiotics.

Skin Microbiota, Immune Cell, and Skin Fibrosis: A Comprehensive Mendelian Randomization Study

BACKGROUND

Microbiota dysbiosis has been reported to lead to leaky epithelia and trigger numerous dermatological conditions. However, potential causal associations between skin microbiota and skin fibrosis and whether immune cells act as mediators remain unclear.

METHODS

Summary statistics of skin microbiota, immune cells, and skin fibrosis were identified from large-scale genome-wide association studies summary data. Bidirectional Mendelian randomization was performed to ascertain unidirectional causal effects between skin microbiota, immune cells, and skin fibrosis. We performed a mediation analysis to identify the role of immune cells in the pathway from skin microbiota to skin fibrosis.

RESULTS

Three specific skin microbiotas were positively associated with skin fibrosis, while the other three were negative. A total of 15 immune cell traits were associated with increased skin fibrosis risk, while 27 were associated with a decreased risk. Moreover, two immune cell traits were identified as mediating factors.

CONCLUSIONS

Causal associations were identified between skin microbiota, immune cells, and skin fibrosis. There is evidence that immune cells exert mediating effects on skin microbiota in skin fibrosis. In addition, some strains exhibit different effects on skin fibrosis in distinct environments.

The Contribution of the Skin Microbiome to Psoriasis Pathogenesis and Its Implications for Therapeutic Strategies

Psoriasis is a common chronic inflammatory skin disease, associated with significant morbidity and a considerable negative impact on the patients' quality of life. The complex pathogenesis of psoriasis is still incompletely understood. Genetic predisposition, environmental factors like smoking, alcohol consumption, psychological stress, consumption of certain drugs, and mechanical trauma, as well as specific immune dysfunctions, contribute to the onset of the disease. Mounting evidence indicate that skin dysbiosis plays a significant role in the development and exacerbation of psoriasis through loss of immune tolerance to commensal skin flora, an altered balance between Tregs and effector cells, and an excessive Th1 and Th17 polarization. While the implications of skin dysbiosis in psoriasis pathogenesis are only starting to be revealed, the progress in the characterization of the skin microbiome changes in psoriasis patients has opened a whole new avenue of research focusing on the modulation of the skin microbiome as an adjuvant treatment for psoriasis and as part of a long-term plan to prevent disease flares. The skin microbiome may also represent a valuable predictive marker of treatment response and may aid in the selection of the optimal personalized treatment. We present the current knowledge on the skin microbiome changes in psoriasis and the results of the studies that investigated the efficacy of the different skin microbiome modulation strategies in the management of psoriasis, and discuss the complex interaction between the host and skin commensal flora.

Modulations of the skin microbiome in skin disorders: A narrative review from a wound care perspective

The cutaneous microbiome represents a highly dynamic community of bacteria, fungi and viruses. Scientific evidence, particularly from the last two decades, has revealed that these organisms are far from being inconsequential microscopic hitchhikers on the human body, nor are they all opportunistic pathogens waiting for the chance to penetrate the skin barrier and cause infection. In this review, we will describe how dermatological diseases have been found to be associated with disruptions and imbalances in the skin microbiome and how this new evidence had shaped the diagnosis and clinical practice relating to these disorders. We will identify the microbial agents which have been found to directly exacerbate skin diseases, as well as those which can ameliorate many of the symptoms associated with dermatological disorders. Furthermore, we will discuss the studies which suggest that bacteriotherapy, either by topical use of probiotics or by bacteria-derived compounds, can rectify skin microbial imbalances, thereby offering a promising alternative to antibiotic treatment and reducing the risks of antibiotic resistance.

Comparative Analysis of the Cutaneous Microbiome in Psoriasis Patients and Healthy Individuals-Insights into Microbial Dysbiosis: Final Results

Psoriasis is one of the most frequent chronic inflammatory skin diseases and exerts a significant psychological impact, causing stigmatization, low self-esteem and depression. The pathogenesis of psoriasis is remarkably complex, involving genetic, immune and environmental factors, some of which are still incompletely explored. The cutaneous microbiome has become more and more important in the pathogenesis of inflammatory skin diseases such as acne, rosacea, atopic dermatitis and psoriasis. Dysbiosis of the skin microbiome could be linked to acute flare ups in psoriatic disease, as recent studies suggest. Given this hypothesis, we conducted a study in which we evaluated the cutaneous microbiome of psoriasis patients and healthy individuals. In our study, we collected multiple samples using swab sampling, adhesive tape and punch biopsies. Our results are similar to other studies in which the qualitative and quantitative changes found in the cutaneous microbiome of psoriasis patients are different than healthy individuals. Larger, standardized studies are needed in order to elucidate the microbiome changes in psoriasis patients, clarify their role in the pathogenesis of psoriasis, decipher the interactions between the commensal microorganisms of the same and different niches and between microbiomes and the host and identify new therapeutic strategies.

Birth and household exposures are associated with changes to skin bacterial communities during infancy

Background and objectives

Microbial exposures during infancy shape the development of the microbiome, the collection of microbes living in and on the body, which in turn directs immune system training. Newborns acquire a substantial quantity of microbes during birth and throughout infancy via exposure to microbes in the physical and social environment. Alterations to early life microbial environments may give rise to mismatches, where environmental, cultural and behavioral changes that outpace the body's adaptive responses can lead to adverse health outcomes, particularly those related to microbiome development and immune system regulation.

Methods

This study explored the development of the skin microbiome among infants born in Chicago, USA. We collected skin swab microbiome samples from 22 mother-infant dyads during the first 48 h of life and again at 6 weeks postpartum. Mothers provided information about social environments and hygiene behaviors that may impact infants' microbial exposures.

Results

Analysis of amplicon bacterial gene sequencing data revealed correlations between infant skin bacterial abundances shortly after birth and factors such as antibiotic exposure and receiving a bath in the hospital. The composition of the infant microbiome at 6 weeks of age was associated with interactions with caregivers and infant feeding practices. We also found shifts in maternal skin microbiomes that may reflect increased hygiene practices in the hospital.

Conclusions and implications

Our data suggest that factors related to the birth and household environment can impact the development of infant skin microbiomes and point to practices that may produce mismatches for the infant microbiome and immune system.

Polyphenol-Rich Cranberry Beverage Positively Affected Skin Health, Skin Lipids, Skin Microbiome, Inflammation, and Oxidative Stress in Women in a Randomized Controlled Trial

This study aimed to determine whether a polyphenol-rich cranberry beverage affects skin properties, lipids, and the microbiome in women using a randomized, double-blinded, placebo-controlled, cross-over design. Twenty-two women with Fitzpatrick skin types 2-3 were randomized to drink a cranberry beverage or placebo for six weeks. After a 21-day washout, they consumed the opposite beverage for six weeks. Six weeks of cranberry beverage significantly reduced UVB-induced erythema, improved net elasticity on the face and forearm, smoothness on the face, and gross elasticity on the forearm compared to the placebo. When stratified by age, these effects of the cranberry beverage were primarily observed in women >40 years old. SOD activities were improved after six weeks of cranberry beverage consumption compared to the placebo, while glutathione peroxide and TNF-α were improved compared to baseline. These effects were found to differ by age group. Skin lipid composition was modulated by both the cranberry beverage and the placebo. Cranberry beverages did not change α- or β-diversity but altered the abundance of several skin microbes at the species and strain level. Consumption of a cranberry beverage for six weeks improved specific skin properties and oxidative stress and modulated skin lipids and microbiome compared to placebo.

Integrated analysis of facial microbiome and skin physio-optical properties unveils cutotype-dependent aging effects

BACKGROUND

Our facial skin hosts millions of microorganisms, primarily bacteria, crucial for skin health by maintaining the physical barrier, modulating immune response, and metabolizing bioactive materials. Aging significantly influences the composition and function of the facial microbiome, impacting skin immunity, hydration, and inflammation, highlighting potential avenues for interventions targeting aging-related facial microbes amidst changes in skin physiological properties.

RESULTS

We conducted a multi-center and deep sequencing survey to investigate the intricate interplay of aging, skin physio-optical conditions, and facial microbiome. Leveraging a newly-generated dataset of 2737 species-level metagenome-assembled genomes (MAGs), our integrative analysis highlighted aging as the primary driver, influencing both facial microbiome composition and key skin characteristics, including moisture, sebum production, gloss, pH, elasticity, and sensitivity. Further mediation analysis revealed that skin characteristics significantly impacted the microbiome, mostly as a mediator of aging. Utilizing this dataset, we uncovered two consistent cutotypes across sampling cities and identified aging-related microbial MAGs. Additionally, a Facial Aging Index (FAI) was formulated based on the microbiome, uncovering the cutotype-dependent effects of unhealthy lifestyles on skin aging. Finally, we distinguished aging related microbial pathways influenced by lifestyles with cutotype-dependent effect.

CONCLUSIONS

Together, our findings emphasize aging's central role in facial microbiome dynamics, and support personalized skin microbiome interventions by targeting lifestyle, skin properties, and aging-related microbial factors. Video Abstract.

Skin Lipid Barrier: Structure, Function and Metabolism

Lipids are important skin components that provide, together with proteins, barrier function of the skin. Keratinocyte terminal differentiation launches unique metabolic changes to lipid metabolism that result in the predominance of ceramides within lipids of the stratum corneum (SC)-the very top portion of the skin. Differentiating keratinocytes form unique ceramides that can be found only in the skin, and generate specialized extracellular structures known as lamellae. Lamellae establish tight hydrophobic layers between dying keratinocytes to protect the body from water loss and also from penetration of allergens and bacteria. Genetic and immunological factors may lead to the failure of keratinocyte terminal differentiation and significantly alter the proportion between SC components. The consequence of such changes is loss or deterioration of skin barrier function that can lead to pathological changes in the skin. This review summarizes our current understanding of the role of lipids in skin barrier function. It also draws attention to the utility of testing SC for lipid and protein biomarkers to predict future onset of allergic skin diseases.

Trifunctional sphingomyelin derivatives enable nanoscale resolution of sphingomyelin turnover in physiological and infection processes via expansion microscopy

Sphingomyelin is a key molecule of sphingolipid metabolism, and its enzymatic breakdown is associated with various infectious diseases. Here, we introduce trifunctional sphingomyelin derivatives that enable the visualization of sphingomyelin distribution and sphingomyelinase activity in infection processes. We demonstrate this by determining the activity of a bacterial sphingomyelinase on the plasma membrane of host cells using a combination of Förster resonance energy transfer and expansion microscopy. We further use our trifunctional sphingomyelin probes to visualize their metabolic state during infections with Chlamydia trachomatis and thereby show that chlamydial inclusions primarily contain the cleaved forms of the molecules. Using expansion microscopy, we observe that the proportion of metabolized molecules increases during maturation from reticulate to elementary bodies, indicating different membrane compositions between the two chlamydial developmental forms. Expansion microscopy of trifunctional sphingomyelins thus provides a powerful microscopy tool to analyze sphingomyelin metabolism in cells at nanoscale resolution.

Nasal symbiont Staphylococcus epidermidis restricts influenza A virus replication via the creation of a polyamine-deficient cellular environment

Studies on the immune-regulatory roles played by the commensal microbes residing in the nasal mucosa consider the contribution of antiviral immune responses. Here, we sought to identify the nasal microbiome, Staphylococcus epidermidis-regulated antiviral immune responses and the alteration of polyamine metabolites in nasal epithelium. We found that polyamines were required for the life cycle of influenza A virus (IAV) and depletion of polyamines disturbed IAV replication in normal human nasal epithelial (NHNE) cells. Inoculation of S. epidermidis also suppressed IAV infection and the concentration of polyamines including putrescine, spermidine, and spermine was completely attenuated in S. epidermidis-inoculated NHNE cells. S. epidermidis activated the enzyme involved in the production of ornithine from arginine and downregulated the activity of the enzyme involved in the production of putrescine from ornithine in nasal epithelium. S. epidermidis also induced the activation of enzymes that promote the extracellular export of spermine and spermidine in NHNE cells. Our findings demonstrate that S. epidermidis is shown to be able of creating an intracellular environment lacking polyamines in the nasal epithelium and promote the balance of cellular polyamines in favor of the host to restrict influenza virus replication.

A New Generation of Postbiotics for Skin and Scalp: In Situ Production of Lipid Metabolites by Malassezia

Effects of pre- and probiotics on intestinal health are well researched and microbiome-targeting solutions are commercially available. Even though a trend to appreciate the presence of certain microbes on the skin is seeing an increase in momentum, our understanding is limited as to whether the utilization of skin-resident microbes for beneficial effects holds the same potential as the targeted manipulation of the gut microflora. Here, we present a selection of molecular mechanisms of cross-communication between human skin and the skin microbial community and the impact of these interactions on the host's cutaneous health with implications for the development of skin cosmetic and therapeutic solutions. Malassezia yeasts, as the main fungal representatives of the skin microfloral community, interact with the human host skin via lipid mediators, of which several are characterized by exhibiting potent anti-inflammatory activities. This review therefore puts a spotlight on Malassezia and provides a comprehensive overview of the current state of knowledge about these fungal-derived lipid mediators and their capability to reduce aesthetical and sensory burdens, such as redness and itching, commonly associated with inflammatory skin conditions. Finally, several examples of current skin microbiome-based interventions for cosmetic solutions are discussed, and models are presented for the use of skin-resident microbes as endogenous bio-manufacturing platforms for the in situ supplementation of the skin with beneficial metabolites.

The Human Skin Microbiome in Health: CME Part 1

Human skin is home to a myriad of microorganisms, including bacteria, viruses, fungi, and mites, many of which are considered commensal microbes that aid in maintaining the overall homeostasis or steady-state condition of the skin and contribute to skin health. Our understanding of the complexities of the skin's interaction with its microorganisms is evolving. This knowledge is based primarily on in vitro and animal studies, and more work is needed to understand how this knowledge relates to humans. Here, we introduce the concept of the skin microbiome and discuss skin microbial ecology, some intrinsic factors with potential influence on the human skin microbiome, and possible microbiome-host interactions. The second article of this two-part CME series describes how microbiome alterations may be associated with skin disease, how medications can affect the microbiome, and what microbiome-based therapies are under investigation.

Changes in oral, skin, and gut microbiota in children with atopic dermatitis: a case-control study

Introduction

Atopic dermatitis (AD) is a common clinical recurrent atopic disease in dermatology, most seen in children and adolescents. In recent years, AD has been found to be closely associated with microbial communities.

Methods

To explore the synergistic effects between colonizing bacteria from different sites and AD, we comparatively analyzed the skin, oral, and gut microbiota of children with AD (50 individuals) and healthy children (50 individuals) by 16S rRNA gene sequencing. Twenty samples were also randomly selected from both groups for metabolic and macrogenomic sequencing.

Results

The results of our sequencing study showed reduced microbiota diversity in the oral, skin, and gut of children with AD (P < 0.05). Metabolomics analysis showed that serotonergic synapse, arachidonic acid metabolism, and steroid biosynthesis were downregulated at all three loci in the oral, skin, and gut of children with AD (P < 0.05). Macrogenomic sequencing analysis showed that KEGG functional pathways of the three site flora were involved in oxidative phosphorylation, ubiquitin-mediated proteolysis, mRNA surveillance pathway, ribosome biogenesis in eukaryotes, proteasome, basal transcription factors, peroxisome, MAPK signaling pathway, mitophagy, fatty acid elongation, and so on (P < 0.05).

Discussion

The combined microbial, metabolic, and macrogenetic analyses identified key bacteria, metabolites, and pathogenic pathways that may be associated with AD development. We provides a more comprehensive and in-depth understanding of the role of the microbiota at different sites in AD patients, pointing to new directions for future diagnosis, treatment and prognosis.

Commensal microbe regulation of skin cells in disease

Human skin is the host to various commensal microbes that constitute a substantial microbial community. The reciprocal communication between these microbial inhabitants and host cells upholds both the morphological and functional attributes of the skin layers, contributing indispensably to microenvironmental and tissue homeostasis. Thus, disruption of the skin barrier or imbalances in the microbial communities can exert profound effects on the behavior of host cells. This influence, mediated by the microbes themselves or their metabolites, manifests in diverse outcomes. In this review, we examine existing knowledge to provide insight into the nuanced behavior exhibited by the microbiota on skin cells in health and disease states. These interactions provide insight into potential cellular targets for future microbiota-based therapies to prevent and treat skin disease.

Microbiological insights and dermatological applications of live biotherapeutic products

As our understanding of dermatological conditions advances, it becomes increasingly evident that traditional pharmaceutical interventions are not universally effective. The intricate balance of the skin microbiota plays a pivotal role in the development of various skin conditions, prompting a growing interest in probiotics, or live biotherapeutic products (LBPs), as potential remedies. Specifically, the topical application of LBPs to modulate bacterial populations on the skin has emerged as a promising approach to alleviate symptoms associated with common skin conditions. This review considers LBPs and their application in addressing a wide spectrum of dermatological conditions with particular emphasis on three key areas: acne, atopic dermatitis, and wound healing. Within this context, the critical role of strain selection is presented as a pivotal factor in effectively managing these dermatological concerns. Additionally, the review considers formulation challenges associated with probiotic viability and proposes a personalised approach to facilitate compatibility with the skin's unique microenvironment. This analysis offers valuable insights into the potential of LBPs in dermatological applications, underlining their promise in reshaping the landscape of dermatological treatments while acknowledging the hurdles that must be overcome to unlock their full potential.

Staphylococcus aureus/Staphylococcus epidermidis from skin microbiota are balanced by Pomegranate peel extract: An eco-sustainable approach

The imbalance in skin microbiota is characterized by an increased number of pathogens in respect to commensal microorganisms. Starting from a skin microbiota collection, the aim of this work was to evaluate the possible role of Pomegranate (Punica granatum L.) Peel Extract (PPE) in restoring the skin microbiota balance acting on Staphylococcus spp. PPE was extracted following green methodology by using n-butane and the Dimethyl Ether (DME) solvents and analyzed for phytochemical composition and antimicrobial activity. The PPE antimicrobial action was evaluated against Gram +, Gram - bacteria and yeast reference strains and the most effective extract was tested against the main skin microbiota isolated strains. PPE extracted with DME showed the best antimicrobial action with MICs ranging from 1 to 128 mg/mL; the main active compounds were Catechin, Quercetin, Vanillic acid and Gallic acid. The PPE in DME anti-adhesive effect was examined against S. epidermidis and S. aureus mono and dual-species biofilm formation by biomass quantification and CFU/mL determination. The extract toxicity was evaluated by using Galleria mellonella larvae in vivo model. The extract displayed a significant anti-adhesive activity with a remarkable species-specific action at 4 and 8 mg/mL against S. epidermidis and S. aureus mono and dual-species biofilms. PPE in DME could represent an eco-sustainable non-toxic strategy to affect the Staphylococcal skin colonization in a species-specific way. The innovation of this work is represented by the reuse of food waste to balance skin microbiota.