The skin microbiome

Outcomes of peripherally inserted central catheter vs conventional central venous catheters in hematological cancer patients: a systematic review and meta-analysis

OBJECTIVE

This review aimed to examine if there is any difference in the risk of thrombosis and central line-associated bloodstream infection (CLABSI) with the use of peripherally inserted central catheter (PICC) and conventional central venous catheters (CVC) in hematological cancer patients.

METHODS

We searched the online databases of PubMed, CENTRAL, Scopus, Web of Science, and Embase for all types of studies comparing the risk of thrombosis and CLABSI between PICC and CVC. The search ended on 23rd September 2024.

RESULTS

Eight studies were included. One was a randomized trial while others were observational studies. Meta-analysis showed no statistically significant difference in the risk of thrombosis between PICC and CVC (OR: 1.69 95% CI: 0.75, 3.82 I2 = 78%). However, these results were not stable on sensitivity analysis. The exclusion of two studies indicated a higher risk of thrombosis with PICC. Pooled analysis showed that the risk of CLABSI was significantly lower with PICC as compared to CVC (OR: 0.52 95% CI: 0.40, 0.66 I2 = 0%). Results of subgroup analysis based on study design and diagnosis showed conflicting results.

CONCLUSIONS

There is conflicting evidence on the risk of thrombosis between PICC and CVC when used for hematological cancer patients. There could be a tendency of higher risk of thrombosis with PICC which needs to be confirmed by further studies. However, the use of PICC may reduce the risk of CLABSI in such patients. The quality of evidence is low owing to the predominance of observational studies with high inter-study heterogeneity.

A multifunctional semi-interpenetrating polymer network hydrogel dressing for wound healing

Hydrogels have exhibited significant application potential in the field of new wound dressings due to their unique physicochemical properties and biological functions. However, traditional hydrogels possess limitations regarding mechanical properties, adhesion, and the promotion of wound healing. Herein, a multifunctional polyvinyl alcohol-tannic acid/polyacrylamide-polydopamine (PVA-TA/PAM-PDA) hydrogels are developed. By combining an amide-rich crosslinked polyacrylamide (PAM) network with a hydroxyl-rich linear polyvinyl alcohol (PVA) structure, a semi-interpenetrating polymer network (semi-IPN) is formed, which serves as a scaffold to enhance mechanical properties. The incorporation of tannic acid (TA) and polydopamine (PDA) into the semi-IPN framework can enhance cell affinity and tissue adhesiveness. This multifunctional composite hydrogel demonstrates outstanding physical and mechanical properties, including excellent elasticity and toughness, stable rheological properties, and favorable swelling properties. It also exhibits strong adhesive properties to various materials and skin, and can promote tissue regeneration and wound healing. This study offers novel ideas for the development and application of multifunctional composite hydrogel wound dressings, and the PVA-TA/PAM-PDA hydrogel shows great promise for clinical applications as an innovative wound dressing.

3D-printed multifunctional bilayer scaffold with sustained release of apoptotic extracellular vesicles and antibacterial coacervates for enhanced wound healing

Full-thickness skin defects pose significant challenges to physical and psychological health while traditional skin grafting techniques are associated with limitations. Herein, we present a 3D-printed multifunctional bilayer scaffold that incorporates apoptotic extracellular vesicles (ApoEVs) and antibacterial coacervates to prevent wound infection and promote wound healing. The ApoEVs were continuously released from the lower layer of the scaffold with large pores to promote angiogenesis and collagen deposition. Meanwhile, the pH-responsive curcumin-containing coacervates were released from the upper layer of the scaffold with dense pores to exert antibacterial and reactive oxygen species scavenging ability. In vivo experiments showed that the scaffold accelerated wound healing and improved healing quality by promoting a more organized collagen arrangement and reducing hyperplastic scar tissue. Furthermore, it effectively reduced hyperplastic scar tissue, resulting in a decrease in the average scar area from 73.3 % to 19.9 %. RNA sequencing analysis revealed that the scaffold upregulated genes associated with cell proliferation and downregulated genes related to inflammation, indicating its potential therapeutic applications for wound healing. This multifunctional bilayer scaffold represents a promising candidate for the treatment of full-thickness skin defects, offering rationales for designing skin scaffolds for regenerative medicine applications.

TEAL-Seq: targeted expression analysis sequencing

Metagenome sequencing enables the genetic characterization of complex microbial communities. However, determining the activity of isolates within a community presents several challenges, including the wide range of organismal and gene expression abundances, the presence of host RNA, and low microbial biomass at many sites. To address these limitations, we developed "targeted expression analysis sequencing" or TEAL-seq, enabling sensitive species-specific analyses of gene expression using highly multiplexed custom probe pools. For proof of concept, we targeted about 1,700 core and accessory genes of Staphylococcus aureus and S. epidermidis, two key species of the skin microbiome. Two targeting methods were applied to laboratory cultures and human nasal swab specimens. Both methods showed a high degree of specificity, with >90% reads on target, even in the presence of complex microbial or human background DNA/RNA. Targeting using molecular inversion probes demonstrated excellent correlation in inferred expression levels with bulk RNA-seq. Furthermore, we show that a linear pre-amplification step to increase the number of nucleic acids for analysis yielded consistent and predictable results when applied to complex samples and enabled profiling of expression from as little as 1 ng of total RNA. TEAL-seq is much less expensive than bulk metatranscriptomic profiling, enables detection across a greater dynamic range, and uses a strategy that is readily configurable for determining the transcriptional status of organisms in any microbial community.IMPORTANCEThe gene expression patterns of bacteria in microbial communities reflect their activity and interactions with other community members. Measuring gene expression in complex microbiome contexts is challenging, however, due to the large dynamic range of microbial abundances and transcript levels. Here we describe an approach to assessing gene expression for specific species of interest using highly multiplexed pools of targeting probes. We show that an isothermal amplification step enables the profiling of low biomass samples. TEAL-seq should be widely adaptable to the study of microbial activity in natural environments.

Utilizing Dual-Channel Graph and Hypergraph Convolution Network to Discover Microbes Underlying Disease Traits

Discovering microbes underlying disease traits opens up opportunities for the diagnosis and effective treatment of diseases. However, traditional methods are often based on biological experiments, which are not only time-consuming but also costly, driving the need for computational frameworks that can accelerate the discovery of these associations. Motivated by these challenges, we propose an innovative prediction algorithm named dual-channel graph and Hypergraph Convolutional Network (DCGHCN) to discover microbes underlying disease traits. First, based on the K-Nearest Neighbors (KNN) principle, we constructed attribute graphs for microbes and diseases, respectively. Next, Graph Convolutional Networks (GCNs) are used to capture homogeneous level implicit representations from attribute graphs of microbes and diseases. We used the output of the GCN layer as input to construct a hypergraph convolutional layer of microbes and diseases, to evaluate the impact of the confirmed microbes and diseases associations (MDAs) on the prediction results. Perform scalar product calculation on the microbe and disease features to determine the predicted score. The innovation of DCGHCN lies in employing the KNN algorithm to handle missing values in the correlation matrix during preprocessing and the use of a dual-channel structure to combine the advantages of GCNs and Hypergraph Convolutional Networks (HGCNs). We used 5-fold cross-validation (CV) to evaluate the performance of DCGHCN. The results showed that the DCGHCN model achieved AUC (Area Under the ROC Curve), AUPR (Area Under the PR Curve), F1-score and accuracy of 0.9415, 0.7637, 0.7515, and 0.9818. We selected two diseases for case studies, and a large number of published literature conclusions confirmed the prediction results of DCGHCN, thus proving that DCGHCN is an effective tool for discovering microbes underlying disease traits.

Rediscovery of viomellein as an antibacterial compound and identification of its biosynthetic gene cluster in dermatophytes

Fungi produce a wide variety of compounds, especially those that exhibit biological activity. Such compounds may aid the survival of fungi in the environment or may contribute to host infection for pathogenic species. Regarding dermatophytes, which affect a large number of patients worldwide, studies on metabolites that exhibit biological activity are scarce. In this study, to gain insight into the interaction with skin microbiota at the site of infection, we searched for compounds that exhibit antibacterial activity among the metabolites of Trichophyton rubrum. We rediscovered viomellein, a red pigment, as a potent antibacterial compound and identified its biosynthetic gene (vio) cluster by RNA-sequencing and gene deletion analyses. Sequential reconstruction of the vio cluster genes in Aspergillus oryzae revealed the biosynthetic pathway for viomellein via nor-toralactone, semivioxanthin, and vioxanthin production. The vio gene cluster is widely conserved among dermatophytes and is also present in some Aspergillus and Penicillium species. Consistent with the results, viomellein and its structural analogs, xanthomegnin, and vioxanthin, were shown to be produced by most dermatophyte species. These results suggest that dermatophytes can produce diverse naphthopyranone compounds, some of which have strong growth inhibitory effects against bacteria. This study provides a previously unknown molecular entity for antibiotic production by dermatophytes and provides insight into the interaction between commensal bacteria and dermatophytes.IMPORTANCEDermatophytes are widespread human pathogens in the world, but the mechanisms of infection have been little studied. Although bacterial density at the site of infection is abundant, interaction between dermatophytes and the bacterial community has not yet been studied. Here, to understand the infection ecology of dermatophytes, we searched for antimicrobial substances that would be effective against the dermal bacterial community. We discovered viomellein, which exhibits strong antibacterial activity against gram-positive bacteria such as Staphylococcus aureus, and its biosynthetic genes are shared not only by dermatophytes but also by other fungi. Since many dermatophytes showed the ability to produce viomellein, it is likely that this is the initial infection strategy of dermatophytes, which has been a mystery for long.

Skin mycobiome: Fungi drive colonization resistance in an already hostile environment

Fungi are an understudied part of the microbiome and can impact host physiology and maintenance of homeostasis. A new study explores how colonization resistance mediated by the fungal skin commensal Malassezia sympodialis exerts evolutionary pressures on Staphylococcus aureus.

Exploring indigenous South African plants as alternative treatments for dermatophytosis: Focusing on the antifungal properties and mechanism of action of Searsia lancea

Numerous medicinal plants are reported to have activity against dermatophytes, however, there are limited studies providing insights into their mechanism of action, which may be hindering their clinical use. This study aimed to investigate the antifungal activity and toxicity of three South African plants traditionally used to treat skin infections caused by dermatophytes and to investigate the mechanism of action of the most active plant extract. Searsia lancea showed the highest antifungal activity against Microsporum canis (MIC 0.156 mg/mL). Warburgia salutaris and M. comosus showed no toxic effects on HaCaT cells while S. lancea exhibited moderate cytotoxicity. The most active combination of S. lancea combined with M. comosus showed to be non-toxic. Searsia lancea and M. comosus were non-mutagenic at 500 μg/mL. The ethyl acetate partition of S. lancea demonstrated a two-fold increase in activity against Microsporum species while fraction fifteen (F15) exhibited a four-fold increase in activity against T. mentagrophytes. Two compounds in F15 were identified as sakuranetin and gentisic acid, with sakuranetin showing the best activity against T. mentagrophytes. Electron microscopy showed alterations of hyphal surfaces in the form of shrinkage and folding of the plasma membrane (24-48 h) and breakage and leakage of cytoplasmic material (72 h). The RT-qPCR showed significant repression (p < 0.01) of the SSU1 gene of M. canis treated with S. lancea (0.312 mg/mL) after 2 and 7 days. The findings not only support traditional usage of S. lancea but also provide targets of S. lancea's anti-dermatophytic activity.

Unique dermal bacterial signature differentiates atopic dermatitis skin from healthy

Gaining a deeper understanding of the variation in skin microbiota across habitats and layers provides critical insights into the complex host-microbial interactions that drive inflammatory skin diseases. Our study investigated dermal versus epidermal microbiota in lesional and non-lesional skin of 37 adult atopic dermatitis (AD) patients and 37 healthy controls. Skin biopsies were partitioned into epidermal and dermal compartments, while serial tape strips collected the superficial epidermis. Bacterial communities were analyzed by cultivation, matrix-assisted laser desorption ionization time-of-flight mass spectrometry, confocal laser scanning microscopy, and metagenomic sequencing. We found that the effects of AD were evident across skin layers. The natural variation between skin layers and habitats diminishes in AD-affected skin, intensifying the impact of the microenvironment and host factors. A remarkably distinct dermal bacterial community was discovered among AD patients, being more conserved and providing a clearer difference between skin habitats, while the epidermis varied substantially. Importantly, comparisons between AD patients and controls revealed more genera differed when studying the dermal samples than the epidermal ones. Staphylococcus, Corynebacterium, and Cutibacterium genera differed with AD status across all samples, but Prevotella and Mitsuokella only differed in the dermis. In the dry and moist dermis, this translated into 14 and 61 gene pathways significantly varying with AD status, including many related to the biosynthesis of menaquinones (vitamin K2). These results suggest dermal sampling would allow for the role of the skin microbiome within AD pathogenesis to be better resolved since these communities are simpler and less prone to environmental contamination.

IMPORTANCE

This study sheds light on the profound impact of skin microbiota's complex composition and distribution in atopic dermatitis (AD). The distinctive bacterial profile and activity, especially within the dermal skin compartment, vividly mirrored the cutaneous conditions in this inflamed microenvironment. The striking similarity in bacterial communities across different skin habitats in atopic skin underscores the high influence of atopic dermatitis-the genetic predisposition to an amplified immune response. This finding suggests that the dermal bacterial profile could be a valuable tool for longitudinally monitoring changes during the disease's relapsing phases, allowing for a precise categorization of patients into specific AD endotypes. Broadening the focus throughout the entire eczema-affected skin paves the way for treatments capable of modulating dermal biological factors, offering more effective management of AD. By further centering the interest in host-microbial interactions, we can refine personalized treatments, ultimately improving the lives of millions suffering from atopic dermatitis.

Skin-associated commensal microorganisms and their metabolites

The skin microbiome is an essential component on our skin and is critical for the maintenance of skin health. It consists of a diverse ecosystem of bacteria, fungi, and viruses. Different body sites in humans exhibit vastly different levels of sebum, temperature and pH, therefore the microbes that colonize these areas have adapted to create a niche for colonization. Healthy microbial diversity is important in the normal function of the skin, and imbalances in microbial diversity in the skin microbiome have been found to correlate with several skin diseases, such as atopic dermatitis, acne vulgaris, psoriasis and chronic wound infections. These microorganisms, especially commensal bacteria, produce various metabolites such as short-chain fatty acids, antimicrobial peptides, siderophores and tryptophan-derived metabolites. These metabolites can interact with and aid the host in processes, such as wound healing and colonization resistance. Metabolites produced by skin commensals have promising therapeutical potential for drug-resistant bacterial infections in place of conventional antibiotics to combat widespread antibiotic resistance. In this review, we will discuss the composition of the skin microbiota and the different classes of metabolites produced by its members, as well as how changes in the skin microbiome impact certain disease conditions.

Effect of Skin Closure with Metal Staples vs. Intradermal Suture on Groin Infections after Vascular Surgery: A Randomised Controlled Trial

OBJECTIVE

Inguinal incision is the most common vascular surgery incision and is associated with a high rate of surgical site infections (SSIs). The objective of this study was to determine whether intradermal suture leads to a lower SSI rate than metal staples.

METHODS

A multicentre, open label, superiority randomised controlled trial was conducted from March 2018 until November 2021 in three Finnish hospitals (ClinicalTrials.gov ID: NCT03468621). Patients with scheduled elective vascular surgery with isolated exposure of the femoral vessels from a longitudinal incision, i.e., femoral endarterectomy, femoral cutdown for endovascular aortic repair, and femoropopliteal or femorofemoral crossover bypass procedure using synthetic graft, were screened for eligibility. Patients were randomised with 1:1 allocation to undergo skin closure with metal staples or continuous intradermal suture. The primary outcome was 30 day SSI rate. SSI was defined according to the US Centers for Disease Control and Prevention (CDC). Secondary outcomes included incision dehiscence and lymphatic leak or seroma.

RESULTS

Three hundred patients aged 54 - 94 years were enrolled (mean age ± standard deviation, 73.4 ± 8.0 years; 217, 72.3% male), with 148 patients randomised to skin closure with intradermal suture and 152 patients to skin closure with metal staples. The SSI rate was 10.1% (15/148) after intradermal suture and 15.8% (24/152) after metal staples (relative risk [RR] 0.64, 95% confidence interval [CI] 0.35 - 1.17; p = .15). The rate of seroma and lymph leak was 12.8% (19/148) and 21.1% (32/152) in the intradermal suture and metal staple groups, respectively (RR 0.6, 95% CI 0.4 - 1.0; p = .060). The rate of inguinal incision complications (infection or dehiscence) was 13.5% (20/148) and 19.7% (30/152) in the intradermal suture and metal staple groups, respectively (RR 0.7, 95% CI 0.4 - 1.2; p = .15).

CONCLUSION

In patients undergoing elective vascular surgery with primary isolated exposure of the femoral vessels, skin closure with intradermal suture did not reduce the SSI rate compared with the use of metal staples.

Assessing the safety of microbiome perturbations

Everyday actions such as eating, tooth brushing or applying cosmetics inherently modulate our microbiome. Advances in sequencing technologies now facilitate detailed microbial profiling, driving intentional microbiome-targeted product development. Inspired by an academic-industry workshop held in January 2024, this review explores the oral, skin and gut microbiomes, focussing on the potential long-term implications of perturbations. Key challenges in microbiome safety assessment include confounding factors (ecological variability, host influences and external conditions like geography and diet) and biases from experimental measurements and bioinformatics analyses. The taxonomic composition of the microbiome has been associated with both health and disease, and perturbations like regular disruption of the dental biofilm are essential for preventing caries and inflammatory gum disease. However, further research is required to understand the potential long-term impacts of microbiome disturbances, particularly in vulnerable populations including infants. We propose that emerging technologies, such as omics technologies to characterize microbiome functions rather than taxa, leveraging artificial intelligence to interpret clinical study data and in vitro models to characterize and measure host-microbiome interaction endpoints, could all enhance the risk assessments. The workshop emphasized the importance of detailed documentation, transparency and openness in computational models to reduce uncertainties. Harmonisation of methods could help bridge regulatory gaps and streamline safety assessments but should remain flexible enough to allow innovation and technological advancements. Continued scientific collaboration and public engagement are critical for long-term microbiome monitoring, which is essential to advancing safety assessments of microbiome perturbations.

Perturbations in the skin microbiome of infantile and adult seborrheic dermatitis and new treatment options based on restoring a healthy skin microbiome

Seborrheic dermatitis (SD) is a common, multifaceted skin condition, but its undefined etiology hampers the development of effective therapeutic strategies. In this review, we describe the intricate relationship between the skin microbiome and the pathogenesis of SD, focusing on the complex interplay between three major groups of organisms that can either induce inflammation (Malassezia spp., Staphylococcus aureus) or else promote healthy skin (Propionibacterium spp.). We describe how the disequilibrium of these microorganisms in the skin microbiome can develop skin inflammation in SD patients. Understanding these complex interactions of the skin microbiome has led to development of novel probiotics (e.g., Vitreoscilla spp. and Lactobacillus spp.) to restore normal skin physiology in SD. There are also differences in the skin microbiomes of healthy and SD infant and adult patients that impact pathogenesis and prompt different management strategies. A deeper understanding of the skin microbiome and its dynamic interactions will provide valuable insights into the pathogenesis of SD and prompt further development of targeted probiotic treatments to restore the balance of the skin microbiome in SD patients.

A Photodermatologic Perspective on Shingles: A Narrative Review Exploring the Skin Microbiome as a Variable in the Effect of UV Radiation on VZV Reactivation

Varicella Zoster Virus (VZV), a member of the herpes virus family, causes varicella (chicken pox) upon primary infection and later manifests as herpes zoster ([HZ] or shingles) upon reactivation. VZV-specific T-cell immunity acquired during primary infection aids recovery, with the virus lying latent in neuronal ganglia until it transports to the skin axonally during reactivation. It has been well-established that reduced T-cell recognition and proliferation, as well as immunosuppression more generally, contribute to VZV reactivation. It has also been discovered that seasonal variation, which is linked to ultraviolet radiation (UVR), correlates with increased HZ cases. This correlation may be explained by the direct immunosuppressant effects of UVR, with melanin offering photoprotective effects that decrease reactivation rates. However, an underexplored aspect of this correlation is the potential role of the skin microbiome in UVR-induced VZV reactivation. Vital for skin homeostasis and immune modulation, the skin microbiome has been found to influence various skin conditions. Preliminary evidence suggests that microbiome diversity may influence VZV reactivation rates, supported by antibiotic-induced effects on HZ incidence. Research also indicates the microbiome's modulating effect on UVR-induced immune suppression, emphasizing its potential significance in VZV reactivation. The skin microbiome's contribution may also help further explain sex and ethnicity-specific variations in VZV reactivation rates. Understanding the interplay between UVR, the skin microbiome, and VZV reactivation warrants further investigation and may help uncover preventive strategies for mitigating VZV reactivation.

Monitoring Skin Volatile Emissions Using Wearable Sensors

Human skin emits a continuous flux of volatile compounds reflecting various metabolic processes in the body, microbial activity, and environmental factors. Harnessing this emission for diagnostics is of great interest given the noninvasive, passive, and accessible nature of the emission, and there is much research underway to understand the value of this skin-emitted volatile organic compound (VOC) matrix. In parallel to this, wearable skin VOC sensors are emerging and garnering attention due to their potential to provide noninvasive, real-time information for monitoring human health, overcoming many of the design challenges related to biofluid monitoring via wearables. The projected opportunities for skin VOCs are fueling innovations in wearable VOC monitoring. This review discusses the most recent developments, from fully integrated wearable skin VOC sensors that exploit existing semiconductor technology to the design and preparation of advanced new sensing materials and devices to deliver new modalities for wearable skin VOC sensors. We articulate the challenges, limitations, and opportunities for technological advances to provide a perspective on promising directions for future developments.

Topical administration of coumarin derivatives alleviates skin inflammatory symptoms in atopic dermatitis model

The prevalence of atopic dermatitis (AD), a chronic inflammatory skin condition, is increasing. Coumarin derivatives, plant secondary metabolites, possess anti-inflammatory properties, but their specific role in AD treatment remain unclear. This study investigated the therapeutic potential of 7-geranyloxycoumarin (C#6), a selective coumarin derivative, in alleviating AD-like symptoms through multifaceted mechanisms. Among various coumarin derivatives tested, C#6 demonstrated remarkable efficacy in both in vitro and in vivo models. Notably, C#6 significantly suppressed interleukin-8 and thymic stromal lymphopoietin production in stimulated HaCaT cells. Experiments on an MC903-induced mouse model of AD revealed that topical administration of C#6 for 10 days led to a significant reduction in ear and epidermal thickness. Flow cytometry analysis showed a significant decrease in CD45 + leukocytes, eosinophils, and Th2 cells in C#6-treated AD mice. Importantly, 16S rRNA sequencing indicated that C#6 restored the disrupted skin microbiome by increasing the abundance of beneficial Lactobacillus and reducing pathogenic bacteria such as Enterobacteriaceae, Corynebacteriaceae, and Corynebacterium, contributing to maintaining skin microbiome balance. Molecular docking studies revealed high binding affinities of C#6 to key regulators, including NOD1, TLR2, PAR2, and TLR3, suggesting a role in modulating critical inflammatory pathways. Additionally, co-culture experiments revealed that C#6 treatment of TNF-α and IFN-γ-stimulated HaCaT cells suppressed inflammatory cytokines expression by THP-1 cells. Collectively, these findings demonstrate that C#6 exerts its anti-atopic effects by suppressing Th2-driven inflammation, reducing eosinophilic infiltration, modulating immune-epidermal crosstalk, and maintaining skin microbiome homeostasis, highlighting its potential as a promising therapeutic agent for AD management.

The spatial and single-cell landscape of skin: Charting the multiscale regulation of skin immune function

Immune regulation is a key function of the skin, a barrier tissue that exhibits spatial compartmentalization of innate and adaptive immune cells. Recent advances in single-cell RNA sequencing (scRNA-seq) and spatial transcriptomics (ST) have facilitated systems-based investigations into the molecular and cellular features of skin immunity at single-cell resolution, identifying cell types that maintain homeostasis in a coordinated manner, and those that exhibit dysfunctional cell-cell interactions in disease. Here, we review how technological innovation is uncovering the multiple scales of heterogeneity in the immune landscape of the skin. The microanatomic scale encompasses the skin's diverse cellular components and multicellular spatial organization, which govern the functional cell interactions and behaviors necessary to protect the host. On the macroanatomic scale, understanding heterogeneity in cutaneous tissue architecture across anatomical sites promises to unearth additional functional immune variation and resulting disease consequences. We focus on how single-cell and spatial dissection of the immune system in experimental models and in humans has led to a deeper understanding of how each cell type in the skin contributes to overall immune function in a context-dependent manner. Finally, we highlight translational opportunities for adopting these technologies, and insights gleaned from them, into the clinic.

Skin Protection Effects of Lactobacillus paragasseri HN910 Lysate and the Role of Alanine

Skin aging is influenced by structural alterations, oxidative stress, inflammation, and microbiome changes, and a comprehensive approach to addressing these factors may be effective for mitigating skin aging. This study evaluates the multifaceted anti-aging effects of heat-killed (HK-HN910) and lysed (LS-HN910) forms of Lactobacillus paragasseri HN910. Protective effects on cell viability, cell permeability, nitric oxide (NO) production, and skin anti-aging gene expression for both HK-HN910 and LS-HN910 were observed. Both forms significantly enhanced tight junction (TJ) protein zonula occludens- 1 (ZO- 1) and antioxidant enzyme glutathione peroxidase (GPx) gene expression, while significantly downregulating that of senescence-associated secretory phenotype pro-inflammatory cytokines interleukin (IL)- 1α, IL- 1β, IL- 6, IL- 8, and tumor necrosis factor-alpha (TNFα). LS-HN910 showed significantly greater upregulation of ZO- 1 and GPx and greater downregulation of IL- 1β and TNFα expression compared to HK-HN910. Cell wall component D-alanine (D-Ala) was released in higher amounts in LS-HN910 than in HK-HN910 and demonstrated anti-aging effects. D-Ala upregulated gene expression of skin barrier ZO- 1, claudin- 1 (Cla- 1), occludin (OCC), filaggrin (FLG), and sphingomyelin phosphodiesterase 2 (SMPD2) and antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), and GPx, while downregulating IL- 1α, IL- 1β, IL- 6, IL- 8, and TNFα. LS-HN910 treatment clinically revealed improvements in anti-aging parameters, including transepidermal water loss, skin water contents, sebum levels, dermal density, eye wrinkle index, skin pH, brightness, and microbiota composition, with a significant increase in Rhodococcus abundance. These findings indicate that LS-HN910, containing released D-Ala, is a promising cosmeceutical for preventing skin aging by enhancing the skin barrier, promoting oxidative defense, modulating inflammatory responses, and influencing skin microbiota.

Skin bacterial community dynamics of hands and forearms before and after military field exercise

The human skin microbiome is crucial for health and immunity, especially under the extreme conditions military personnel face. Soldiers often encounter unique stressors and hygienic challenges that can alter their skin's microbial composition, particularly in field environments. In this study, we aimed to investigate the impact of military field exercises on the diversity and composition of the skin bacterial microbiota using 16S rRNA sequencing. We conducted a longitudinal study of Norwegian soldiers (n = 19) participating in outdoor training operations during the NATO winter exercise Cold Response 2022. Skin swabs were taken from soldiers' hands and forearms before and after the 10-day military exercise, and following a 3-week post-exercise leave. Our results reveal hand- and forearm-specific shifts in bacterial populations associated with the exercise, likely influenced by environmental exposure, reduced hygiene, and heightened social contact. Alpha diversity increased on forearms while remaining stable on hands, which appeared more resilient to perturbations. Both sites exhibited temporal changes in composition, with soil- and water-associated bacteria enriched post-exercise; most being transient on hands but more sustained on forearms. The soldiers' microbiomes converged during the exercise, then diverged in the post-exercise leave period, and neither skin site returned to baseline composition at follow-up. Our findings highlight the impact of collaborative outdoor activities on microbial communities and suggest that resilience and stability differ between skin sites.IMPORTANCEOptimizing soldier health and resilience is critical for maintaining military readiness and operational effectiveness. The skin, as the body's first line of defense, is subjected to numerous challenges in military environments. Unique environmental and hygiene challenges can disrupt the skin microbiome and increase susceptibility to skin and soft tissue infections. This longitudinal research provides valuable insights into the effects of military service on the bacterial dynamics of the skin microbiome but can also inform hygiene management and disease prevention in comparable situations.

Matrix Dynamics and Microbiome Crosstalk: Matrix Metalloproteinases as Key Players in Disease and Therapy

Matrix metalloproteinases (MMPs) are key enzymes involved in extracellular matrix (ECM) remodeling, regulating a wide range of cellular and immune processes in both homeostatic and pathological conditions. Host-microbiota interactions play a critical role in maintaining ECM balance; however, during dysbiosis, this regulation is disrupted, leading to compromised barrier integrity, pathogen translocation into circulation, and the development of systemic diseases and cancer. This review highlights the bidirectional relationship between MMP expression/activity and microbiota dysbiosis, emphasizing tissue-specific alterations in MMP activity that contribute to disease progression. In addition, it integrates interdisciplinary evidence to illustrate the MMP-dependent mechanisms underlying various pathologies associated with oral and gut microbiome dysbiosis, including long-range effects through the gut-skin and gut-brain axes. Thus, this review introduces the emerging field of MatrixBiome, which explores the complex interactions between the ECM, microbiota, and host tissues. Finally, it also outlines therapeutic strategies to modulate MMP levels, either indirectly through microbiome-targeted approaches (e.g., prebiotics, probiotics, and postbiotics) or directly using MMP inhibitors, offering promising avenues for future clinical interventions.

Skin Microbiome Overview: How Physical Activity Influences Bacteria

The skin cannot be considered as just a barrier that protects against physical, chemical, and biological damage; it is a complex and dynamic ecosystem that varies across lifespans. Interest in the relationship between physical activity and skin microbiota has grown significantly in recent years. The skin microbiota has a crucial role in skin functions and physiology, and an imbalance, known as dysbiosis, is correlated with several diseases, such as inflammatory bowel disease (IBD), infectious disease, obesity, allergic disorders, and type 1 diabetes mellitus. Among the causes of dysbiosis, the practice of physical exercise, especially in contact sports, including wrestling, artistic gymnastics, and boating, certainly represents a predisposing factor for infectious disease. This review aims to provide an overview of the skin microbiota and its regulation, focusing on interactions between physical exercise and skin microbiota, the antimicrobial peptides (AMPs) as regulators of skin microbiota, and the impact of probiotics supplementation on physical performance.

Hydrogel Containing Biogenic Silver Nanoparticles and Origanum vulgare Essential Oil for Burn Wounds: Antimicrobial Efficacy Using Ex Vivo and In Vivo Methods Against Multidrug-Resistant Microorganisms

Background/Objectives: Wounds from burns are susceptible to infections, allowing multidrug-resistant microorganisms to complicate treatments and patient recovery. This highlights the development of new strategies to control these microorganisms. This work evaluated the antibacterial activity of hydrogels containing biogenic silver nanoparticles (bio-AgNP) and Origanum vulgare essential oil (OEO) against multidrug-resistant bacteria. Methods: The formulations were subjected to organoleptic, pharmacotechnical, and stability characterization and antimicrobial activity assessment by time-kill tests and alternative methods, an ex vivo model using porcine skin, and an in vivo model using Galleria mellonella. Results: All hydrogels maintained their stability after the thermal stress. The hydrogel containing bio-AgNP + OEO 1% (HAgNP + OEO1) presented bactericidal effectiveness, within 2 h, against both Gram-positive and Gram-negative multidrug-resistant bacteria in the time-kill test. For alternative testing, HAgNP + OEO1 was compared with 1% silver sulfadiazine (SS) and the base formulation. In the ex vivo test, both HAgNP + OEO1 and SS treatments showed a similar reduction in superficial washing of the burn for S. aureus 999, while for P. aeruginosa, the reduction was more expressive for SS treatment. In the burn tissue, HAgNP + OEO1 treatment was more effective against S. aureus 999, while for P. aeruginosa 1461, both formulations were similarly effective. In the Galleria mellonella test, survival rates after 48 h were 84% for the control group (base) and 50% for both HAgNP + OEO1 and SS treatment groups. Conclusions: This study demonstrates that the hydrogel combining antimicrobials is effective against multidrug-resistant microorganisms, offering a promising alternative for the treatment of infected burns.

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.

Enhancement of burn wound healing using optimized bioactive probiotic-loaded alginate films

Wound infection can prolong the healing process, leading to various complications. Although the use of antibiotics is common, it presents challenges such as poor pharmacokinetics. The prevalence of antibiotic resistance has further complicated wound management. Studies have demonstrated the potential of topical probiotics; however, stabilizing these cells and creating appropriate conditions for their colonization are essential. In this study, polymeric films were utilized to immobilize probiotics and provide an effective dressing. Aloe vera gel was incorporated into the films to enhance anti-inflammatory activity and probiotic viability. The optimal film was developed using sodium alginate and zinc chloride, with manufacturing parameters optimized to achieve the highest cell viability and suitable properties through the D-optimal method. The models were verified by comparing the actual and predictive responses of the optimized formulation. The optimal film was characterized using microscopic, mechanical, and microbial examinations. The cross-linked alginate matrix improved the stability of probiotics during storage. In vivo tests demonstrated that the formulation could reduce microbial counts and shorten healing duration. This dressing improved wound healing with immobilized probiotics and aloe vera gel, offering promising directions for future research on advanced biomaterials to enhance wound care and combat antibiotic resistance.

No detrimental effect on the hand microbiome of health care staff by frequent alcohol-based antisepsis

BACKGROUND

The importance of ethanol-based hand rubs (EBHRs) to prevent health care-associated infections is undisputed. However, there is a lack of meaningful data regarding the influence of EBHRs on skin microbiome.

METHODS

Four nurses in a neonatal intensive care unit were included. After a leave of 14 days, samples were taken before the first hand rubbing action and at the end of shift, with continued sampling on days 1, 7, and 28. To analyze the hand microbiome, microbial cells were collected using the glove-juice technique. Pro- and eukaryotic community profiles were created using amplicon sequencing of 16S and 18S ribosomal RNA (rRNA) gene markers.

RESULTS

On average, hand antisepsis was performed 108 times per 8-hour work shift. Microbial communities were dominated by typical taxa found on human skin. In addition, a clear nurse-specific (ie, individual) microbiome signature could be observed. For Prokaryota, daily exposure led to the end-of-the-day microbiomes being more similar to each other across nurses. In contrast, longitudinal effect of 28-day application revealed more similarity of the Eukaryotic community.

CONCLUSIONS

Frequent occupational use of EBHR did not adversely affect the composition of the human hand microbiome. Thus, daily hand antisepsis retains its significance as the most important procedure for infection control.

Pathogenesis of systemic sclerosis: an integrative review of recent advances

Systemic sclerosis (SSc), or scleroderma, is a complex autoimmune connective tissue disease characterized by autoimmunity, vasculopathy, and progressive organ fibrosis, leading to severe organ dysfunction. The disease begins with a vascular injury triggered by autoimmune responses and environmental factors against a backdrop of genetic predisposition. This injury impairs angiogenesis and vasculogenesis, resulting in capillary loss and arteriolar constriction, which promotes immune cell infiltration and sustained inflammation within affected tissues. These vascular anomalies cause severe complications, including pulmonary artery hypertension, scleroderma renal crisis, and skin ulcers. Chronic inflammation fosters persistent fibroblast activation, resulting in extensive fibrosis that defines SSc. This review synthesizes the latest research on pathogenesis of SSc, highlighting the shift from fundamental research to a precision therapeutic approach. It explores the potential of technologies like flow cytometry and single-cell RNA sequencing to investigate pathogenic cell subtypes. These platforms integrate transcriptomic, genomic, proteomic, and epigenomic data to uncover insights into the underlying mechanisms of SSc pathogenesis. This review advocates for a multidisciplinary, patient-centric approach that harnesses recent scientific advances, directing future SSc research toward personalized and precise interventions.

Comparative gut microbiome research through the lens of ecology: theoretical considerations and best practices

Comparative approaches in animal gut microbiome research have revealed patterns of phylosymbiosis, dietary and physiological convergences, and environment-host interactions. However, most large-scale comparative studies, especially those that are highly cited, have focused on mammals, and efforts to integrate comparative approaches with existing ecological frameworks are lacking. While mammals serve as useful model organisms, developing generalised principles of how animal gut microbiomes are shaped and how these microbiomes interact bidirectionally with host ecology and evolution requires a more complete sampling of the animal kingdom. Here, we provide an overview of what past comparative studies have taught us about the gut microbiome, and how community ecology theory may help resolve certain contradictions in comparative gut microbiome research. We explore whether certain hypotheses are supported across clades, and how the disproportionate focus on mammals has introduced potential bias into gut microbiome theory. We then introduce a methodological solution by which public gut microbiome data of understudied hosts can be compiled and analysed in a comparative context. Our aggregation and analysis of 179 studies shows that generating data sets with rich host diversity is possible with public data and that key gut microbes associated with mammals are widespread across the animal kingdom. We also show the effects that sample size and taxonomic rank have on comparative gut microbiome studies and that results of multivariate analyses can vary significantly with these two parameters. While challenges remain in developing a universal model of the animal gut microbiome, we show that existing ecological frameworks can help bring us one step closer to integrating the gut microbiome into animal ecology and evolution.

Pathophysiology and Prevention of Ventriculostomy-Related Infections: A Review

This qualitative review aims to summarize current knowledge on ventriculostomy-related infection (VRI) pathophysiology and its prevention. VRI generally occurs at day 10, mainly because of Gram-positive cocci , after a cerebrospinal fluid leak. Skin microbiota and biofilm seem to play a major role in VRI pathogenesis. Colonization of external ventricular drain by biofilm is universal and occurs quickly after catheter insertion. However, pathogens from the skin are more often associated with VRI than commensal bacteria. A review of proposed preventive measures shows that none has proven to be fully efficient. Periprocedural and prolonged systemic prophylactic antimicrobials have not shown to prevent VRIs and may promote the emergence of more resistant or pathogenic strains. Antimicrobial and silver-impregnated external ventricular drains, although promising, have not demonstrated preventive effects and may modify bacterial ecology. These results are consistent with the proposed pathophysiology. Finally, we will present a few propositions for future research that may help in improving our knowledge and thus better prevent VRIs. Until then, given the available data, limiting the duration of ventricular drainage may be the most attainable option to prevent VRIs.

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.

Impact of maternal obesity and mode of delivery on the newborn skin and oral microbiomes

Introduction. Previous studies have shown vast differences in the skin and oral microbiomes of newborns based on delivery method [Caesarean section (C-section) vs vaginal]. Exposure to or absence of certain bacteria during delivery can impact the neonate's future susceptibility to infections, allergies or autoimmunity by altering immune functions. Few studies have focused on the impact of maternal obesity on the variations of newborn skin and oral microbiomes. Obese pregnant women typically have a higher vaginal microbiome diversity, and their pregnancies are at higher risk for adverse outcomes and complications.Hypothesis. We hypothesized that the skin and oral microbiomes of newborns born to obese mothers would include more diverse, potentially pathogenic bacteria and that the skin and oral microbiome in C-section delivered newborns would be less diverse than vaginally delivered newborns.Aim. We aim to begin to establish maternal obesity and mode of delivery as factors contributing to increased risk for negative newborn outcomes through impacts on newborn bacterial dysbiosis.Methodology. A skin swab was collected immediately following delivery of 39 newborns from 13 healthy weight body mass index (BMI 18.50-24.99), 11 overweight (BMI 25.0-29.99) and 15 obese (BMI ≥30.00) pregnant participants. An oral swab was collected immediately following delivery for 38 of these newborns from 13 healthy weight, 10 overweight and 15 obese pregnant participants. Bacterial genera were identified via 16S rRNA amplicon sequencing.Results. The newborn skin microbiome was comprised of typical skin bacteria (i.e. Corynebacterium). Newborns of obese participants had a higher relative abundance of Peptoniphilus in their skin microbiome compared to newborns of healthy weight participants (P=0.007). Neonates born via C-section had a higher relative abundance of Ureaplasma in their oral microbiome compared to neonates delivered vaginally (P=0.046).Conclusion. We identified differences in the newborn skin and oral microbiomes based on pre-pregnancy BMI and method of delivery. These differences could be linked to an increased risk of allergies, autoimmune disease and infections. Future longitudinal studies will be crucial in determining the long-term impact of these specific genera on newborn outcomes. Understanding these connections could lead to targeted interventions that reduce the risk of adverse outcomes and improve overall health trajectory.

Little Peacemakers: Microbes Can Promote Nonviolent Conflict Resolution by Their Hosts

Conflicts between individuals of the same species are common in nature and are mostly resolved with limited aggression. Several theoretical studies, such as the Hawk-Dove (HD) game model, investigate the evolution of limited aggression expressed during conflicts between individuals. These studies mainly focus on the individuals involved in the conflict and their genes. Recently accumulating evidence indicates that microbes are associated with diverse functions of their host and can affect host behavior. Here we extend the classic HD game model to include both the hosts and their microbes, examining how natural selection acts on the microbes. We find that nonaggressive host behavior is more likely to evolve and spread in a population when induced by the microbes residing in the host, compared to nonaggressive behavior induced by host genes. Horizontal transmission allows microbes to colonize new hosts, making their success dependent on the fitness of both the host and its opponent. Therefore, selection on the microbes favors reduced host aggressiveness under wider conditions compared to selection acting on genes alone. Our results suggest that microbes may help explain the ubiquity of nonviolent conflict resolution. Consequently, factors that alter the microbial composition within hosts may affect the aggressiveness level in host populations.

The Beneficial Effects of a N-(1-Carbamoyl-2-phenyl-ethyl) Butyramide on Human Keratinocytes

Background: The skin microbiota-derived metabolite butyrate plays a pivotal role in maintaining skin health. Unfortunately, unpleasant sensorial properties and unfavorable physicochemical properties strongly limit the butyrate use in dermatology clinical practice. This study investigates the effects of N-(1-carbamoyl-2-phenyl-ethyl) butyramide (FBA), a butyric acid releaser with neutral sensorial properties on skin keratinocyte function. Methods: Immortalized human keratinocyte cell line (HaCaT cells) was treated with FBA at various concentrations (0.001-1 mM) and time points (6-48 h). Cellular proliferation was assessed using MTT assays, while barrier integrity was evaluated by measuring tight junction proteins (occludin and ZO-1). Oxidative stress was analyzed using ROS assays and Western blot for Nrf2 and NF-κB expression. Markers of differentiation and extracellular matrix proteins were measured via quantitative PCR and wound-healing capability was assessed using a scratch assay. Results: FBA significantly enhanced keratinocyte proliferation at an optimal concentration of 0.1 mM. Tight junction protein expression increased, indicating improved barrier function. FBA reduced oxidative stress by upregulating Nrf2 and suppressing NF-κB activity. It also promoted the expression of differentiation markers (e.g., keratin-1, filaggrin) and extracellular matrix proteins (e.g., collagen type I and elastin). Furthermore, FBA accelerated wound closure, demonstrating its efficacy in enhancing the mechanisms of skin repair. Conclusions: Our results demonstrate that FBA enhances human keratinocyte cell differentiation, proliferation, and skin repair while protecting against oxidative stress. Its potential in cosmetics lies in delivering butyric acid benefits without organoleptic limitations, with possible applications in several skin condition characterized by deficient butyrate production and inflammation, such as atopic dermatitis.

Effects of snake fungal disease (ophidiomycosis) on the skin microbiome across two major experimental scales

Emerging infectious diseases are increasingly recognized as a significant threat to global biodiversity conservation. Elucidating the relationship between pathogens and the host microbiome could lead to novel approaches for mitigating disease impacts. Pathogens can alter the host microbiome by inducing dysbiosis, an ecological state characterized by a reduction in bacterial alpha diversity, an increase in pathobionts, or a shift in beta diversity. We used the snake fungal disease (SFD; ophidiomycosis), system to examine how an emerging pathogen may induce dysbiosis across two experimental scales. We used quantitative polymerase chain reaction, bacterial amplicon sequencing, and a deep learning neural network to characterize the skin microbiome of free-ranging snakes across a broad phylogenetic and spatial extent. Habitat suitability models were used to find variables associated with fungal presence on the landscape. We also conducted a laboratory study of northern watersnakes to examine temporal changes in the skin microbiome following inoculation with Ophidiomyces ophidiicola. Patterns characteristic of dysbiosis were found at both scales, as were nonlinear changes in alpha and alterations in beta diversity, although structural-level and dispersion changes differed between field and laboratory contexts. The neural network was far more accurate (99.8% positive predictive value [PPV]) in predicting disease state than other analytic techniques (36.4% PPV). The genus Pseudomonas was characteristic of disease-negative microbiomes, whereas, positive snakes were characterized by the pathobionts Chryseobacterium, Paracoccus, and Sphingobacterium. Geographic regions suitable for O. ophidiicola had high pathogen loads (>0.66 maximum sensitivity + specificity). We found that pathogen-induced dysbiosis of the microbiome followed predictable trends, that disease state could be classified with neural network analyses, and that habitat suitability models predicted habitat for the SFD pathogen.

Microecology in vitro model replicates the human skin microbiome interactions

Skin microecology involves a dynamic equilibrium among the host, microbiome, and internal/external environments. This equilibrium, shaped by multifactorial interactions, reflects individual specificity and diversity. Creating a replicable in vitro skin microecological model is highly challenging. Here, we introduce a mimicked stratum corneum microecology model (SCmic). It uses light cured crosslinked hydrogels as a scaffold and moisture source, and nonviable epidermal cells as the main nutrient. This setup establishes a suitable, stable, and reproducible microecology for microbiome colonization. Notably, it replicates the normal/oily skin microbiota with no significant differences from the original native microbiota at the genus level. Simultaneously, we have developed a standardized human skin microbiota model (Hcm), featuring seven dominant strains that form a representative microbial community. The models provide highly convenient approaches for exploring the intricate mutual interactions among skin microecology, influence of microbiota on skin health, and metabolism of chemical substances by microbiota.

Chronological maturation of the skin immune barrier is topographically different

Adult skin varies across regions, with differences in chemical, physical, microbiota, and immune barriers. However, data on topographical immune differences in other age groups are limited. This study aimed to explore the chronological maturation of the immune barrier in various skin regions. A TaqMan low-density array and immunohistochemical and immunofluorescence detection of various immune cells and mediators in sebaceous gland-rich (SGR) and gland-poor (GP) healthy skin were performed in children, adolescents, and adults. The maturation of SGR skin showed a general upward trend in the mRNA levels of most Th17-related molecules with a significant increase in IL-1B from childhood to adulthood, but with only a slight elevation between childhood and adolescence. In addition, T cell, Treg, dendritic cell (DC) counts, as well as the levels of several Th17-related proteins (IL-17, IL-10, IL-23, CCL20, S100A8, sfTSLP, LCN2), increased significantly with age. In GP skin, AHR mRNA levels decreased, while Th17-related protein levels increased, although only moderately. When comparing the two regions, SGR and GP skin were similar in childhood, with differences emerging in adolescence and becoming significant in adulthood, particularly in the IL-17 pathway, mainly produced by Th17 cells. Our results show a similarly directed maturation process in GP and SGR regions, with more pronounced development of the SGR skin immune barrier (with more immune cell infiltration and cytokine production) during and after the adolescence. This is likely to be related to the significant changes in the chemical and microbiota barriers of the SGR skin during adolescence, and may explain the high incidence of inflammatory skin diseases on the SGR skin of adolescents, highlighting the need for targeted skin care in this region.

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.

Isolation, characterization, and genomic analysis of three novel Herelleviridae family lytic bacteriophages against uropathogenic isolates of Staphylococcus saprophyticus

BACKGROUND

Staphylococcus saprophyticus (S. saprophyticus) is the second most prevalent etiological agent of urinary tract infections (UTIs) in young women. However, there is a paucity of data regarding its bacteriophage (phage). Therefore, this study was conducted to isolate and identify new lytic phages from municipal wastewater with the objective of increasing knowledge about phages and their genomes.

METHODS

A total of 11 clinical isolates of S. saprophyticus and 30 wastewater samples were used to isolate three lytic phages (vB_SsapH-Golestan-100, vB_SsapH-Golestan101-M, and vB_SsapH-Golestan-105-M). The morphology, behavioral characteristics, and complete DNA genomes of these phages were analyzed.

RESULTS

The microscopic images of the phages revealed that the sizes of their heads and tail lengths fell within the ranges of 90-111 nm and 234-266 nm, respectively. All phages exhibited high adsorption rates (99.5% in 15 min) and burst sizes (150-210 PFU per infected cell), with a potential for a narrow host range. Genomic analysis of Staphylococcus phages indicated a size of 136,433 base pairs (bp) with a guanine-cytosine (GC) content of 33.7% and 192 open reading frames (ORFs) for vB_SsapH-Golestan-100, 144,081 bp with a GC content of 29.6% and 205 ORFs for vB_SsapH-Golestan101-M, and 142,199 bp with a GC content of 30.6% and 203 ORFs for vB_SsapH-Golestan-105-M. A bioinformatics analysis indicated that all three phages belong to the Twortvirinae subfamily of Herelleviridae. Among the three phages, vB_SsapH-Golestan-100 exhibited the least similarity to previously known phages, with less than 21% similarity with its closest counterparts in genomic databases.

CONCLUSIONS

This study identified new phages that have the ability to destroy a broad range of S. saprophyticus isolates and may potentially be classified as a new genus and species within the Herelleviridae family in future studies.

Insights into Liposomal and Gel-Based Formulations for Dermatological Treatments

Dermatological diseases pose a significant challenge due to their chronic nature, complex pathophysiology, and the need for effective, patient-friendly treatments. Recent advancements in liposomal and gel-based formulations have played a crucial role in improving drug delivery, therapeutic efficacy, and patient compliance. Liposomal formulations have garnered considerable attention in dermatology due to their ability to encapsulate both hydrophilic and lipophilic compounds, enabling controlled drug release and enhanced skin penetration. However, challenges such as formulation complexity, stability issues, and regulatory constraints remain. Similarly, gel-based formulations are widely used due to their ease of application, biocompatibility, and ability to retain active ingredients. However, they also face limitations, including restricted penetration depth, susceptibility to microbial contamination, and challenges in achieving sustained drug release. The integration of liposomal and gel-based technologies offers a promising strategy to overcome current challenges and optimize dermatological drug delivery. This review explores both well-established therapies and recent innovations, offering a comprehensive overview of their applications in the treatment of prevalent dermatological conditions. Ultimately, continued research is essential to refine these formulations, expanding their clinical utility and enhancing therapeutic effectiveness in dermatology.

Microbiome and Postbiotics in Skin Health

The skin microbiome, a diverse and dynamic ecosystem of microorganisms, plays a pivotal role in maintaining skin health by interacting with skin cells, immune components, and structural barriers. It is essential for skin homeostasis, immune defense, and protection against pathogenic colonization. Dysbiosis in the microbiome has been implicated in numerous dermatological conditions, including acne, eczema, psoriasis, and rosacea. Acne, the most prevalent skin condition, affects up to 85% of individuals at some point in their lives, while eczema and psoriasis impose significant public health and economic burdens. The composition of the skin microbiome varies across skin types and anatomical sites, with sebaceous, moist, and dry areas fostering distinct microbial communities. Emerging therapeutic strategies such as microbiome-targeted treatments offer novel avenues for addressing skin diseases. Among these approaches, postbiotics have gained significant attention for their safety and efficacy. Unlike probiotics, postbiotics are non-viable microbial cells or their metabolites, which reduce safety concerns while providing functional benefits such as UV protection and wound healing. This review consolidates current insights into the role of the skin microbiome in health and disease, emphasizing postbiotics as a promising therapeutic strategy by exploring the clinical and commercial potential of microbiome-based treatments, particularly postbiotics, and their ability to redefine dermatological care and improve patient outcomes.

Antimicrobial and anti-inflammatory effects of polyethyleneimine-modified polydopamine nanoparticles on a burn-injured skin model

Chronic infections involving bacterial biofilms pose significant treatment challenges due to the resilience of biofilms against existing antimicrobials. Here, we introduce a nanomaterial-based platform for treating Staphylococcus epidermidis biofilms, both in isolation and within a biofilm-infected burn skin model. Our approach leverages biocompatible and photothermal polydopamine nanoparticles (PDNP), functionalized with branched polyethyleneimine (PEI) and loaded with the antibiotic rifampicin, to target bacteria dwelling within biofilms. A key innovation of our method is its ability to not only target planktonic S. epidermidis but also effectively tackle biofilm-embedded bacteria. We demonstrated that PDNP-PEI interacts effectively with the bacterial surface, facilitating laser-activated photothermal eradication of planktonic S. epidermidis. In a 3D skin burn injury model, PDNP-PEI demonstrates anti-inflammatory and reactive oxygen species (ROS)-scavenging effects, reducing inflammatory cytokine levels and promoting healing. The rifampicin-loaded PDNP-PEI (PDNP-PEI-Rif) platform further shows significant efficacy against bacteria inside biofilms. The PDNP-PEI-Rif retained its immunomodulatory activity and efficiently eradicated biofilms grown on our burn-injured 3D skin model, effectively addressing the challenges of biofilm-related infections. This achievement marks a significant advancement in infection management, with the potential for a transformative impact on clinical practice.

Protocol for the development, assembly, and testing of a synthetic skin microbial community

A reproducible study system is essential for understanding the role of microbes in human skin health and disease. We present a protocol for constructing a synthetic microbial community (SkinCom) of nine strains dominant to native human skin microbiome. We describe steps for computing growth metrics, constructing communities, and extracting DNA and library preparation for shotgun sequencing. We detail steps for data preprocessing and analysis of community samples. We illustrate SkinCom's application with an epicutaneous murine model and downstream multiomic analysis. For complete details on the use and execution of this protocol, please refer to Lekbua et al.1.

Effects of Two Different Basic Skincare Regimens on Children and Adult Skin Microbiota: An Exploratory Randomized Controlled Crossover Trial

INTRODUCTION

Regular use of leave-on skincare products has positive effects on the skin barrier and appears to influence the skin microbiome in atopic dermatitis (AD). However, product-related effects on the skin microbiome are unclear. The aim of this study was to investigate to which extent the application of an emollient plus product differs from a petrolatum-based basic skincare product in terms of skin physiology, skin barrier, and skin microbiome.

METHODS

In an exploratory study regime, 50 subjects (children and adults) with mild AD were randomized to receive Bepanthen SensiDaily® (BSD) and Basiscreme DAC (DAC) for 3 months in a crossover design. Skin physiological measurements and skin microbiome swabs were taken on the forearm and lower leg before and after each 3-month application period of the respective product.

RESULTS

Improvement of skin physiological parameters after 3 months was observed in both topical leave-on product groups. Statistically significant differences were observed in baseline microbiomes between children and adults (p < 0.001) but not between the product groups.

CONCLUSION

Regular application of leave-on products leads to better stratum corneum hydration after 3 months with better effects of BSD on the forearms of children and the lower legs of adults compared to DAC. The application of BSD and DAC did not lead to significant alterations in the overall composition of the skin microbiome. Although there were shifts in the frequency of certain microbial genera, these changes were not consistent between age groups and treatments.

The Expanding Role of Probiotics in Human Health

Since the 1990s, it has been widely documented that probiotics, either alone or in combination with prebiotic supplements, play a vital role in host health and disease management [...].

Hand-to-surface bacterial transfer and healthcare-associated infections prevention: a pilot study on skin microbiome in a molecular biology laboratory

Background

Healthcare-associated infections (HAIs) are a major global public health problem, contributing significantly to patient morbidity and mortality. This study analyses differences in type and amounts of bacteria transferred from volunteers' dominant palm to two healthcare-relevant surfaces (glass and laminate table), both before and after hand washing with water and antibacterial soap. The aim was to understand hand-to-surface microbial contamination and support the development of HAI prevention strategies.

Methods

Microbial DNA was extracted and sequenced to identify bacteria species. Taxonomic and statistical analyses were performed to evaluate bacterial diversity and abundance across the experimental groups.

Results

The results confirmed greater bacteria abundance and species richness on palm compared to surfaces, with a significant reduction after hand washing, especially on glass. Taxa analysis highlighted the increased persistence of Gram-negative HAIs-related bacteria on laminate surface, while Gram-positive opportunistic bacteria were more abundant on palms and glass surface. Beta diversity confirmed significant differences in microbial composition between the groups, highlighting the importance of bacteria-surface characteristics in designing preventive measures.

Conclusion

Despite some limitations, our study emphasizes the importance of microbiological surveillance for all opportunistic bacteria with pathogenic potential. These findings can contribute to more effective guidelines for surface disinfection and hand washing, key elements in preventing HAIs.

Amplicon-based analysis reveals link between adolescent acne and altered facial skin microbiome induced by negative emotional states

Introduction

The skin microbiome is integral to maintaining skin homeostasis and is involved in the pathogenesis of acne. Emerging evidence supporting the 'brain-skin axis' suggests that psychological stress may exacerbate acne. Both negative emotional states and acne are highly prevalent among adolescents. Although research has begun to explore this relationship, the role of the skin microbiome in adolescents experiencing emotional disturbances and acne remains poorly understood.

Methods

166 adolescents aged 15-18 were divided into four distinct groups based on their emotional health and acne severity: no acne or negative emotions (NC), acne without negative emotions (NS), negative emotions without acne (YC), and acne with negative emotions (YS). Skin samples were collected from each participant's forehead and analyzed using high-throughput sequencing techniques, followed by comprehensive bioinformatics analyses to evaluate the microbial composition and diversity across the different groups.

Results

Adolescents with both acne and negative emotions exhibited significantly higher acne severity (IGA 2.675 ± 0.090) compared to the group with acne but without negative emotions (IGA 1.952 ± 0.136). Distinct microbial community patterns emerged among the groups, with acne-affected individuals displaying increased α-diversity. Additionally, negative emotions were associated with heightened β-diversity differences between acne-affected individuals. The predominant bacterial phyla identified were Firmicutes, Bacteroidetes, Proteobacteria, and Fusobacteria, with Acinetobacter being more abundant, and Roseomonas and Cutibacterium being less prevalent in adolescents experiencing negative emotions.

Conclusion

This study revealed that the bacterial biomarkers of the disease change when acne is accompanied by negative emotions. Cutibacterium, Acinetobacter, and Roseomonas may be key contributors to acne exacerbation. These findings underscore the importance of considering both emotional and microbiological factors in the management of adolescent acne, particularly within the context of the brain-skin connection.

The Neovaginal Microbiota, Symptoms, and Local Immune Correlates in Transfeminine Individuals with Penile Inversion Vaginoplasty

Transfeminine people (assigned male at birth) often undergo penile inversion vaginoplasty to create vulva, a clitoris and a vaginal canal (referred to as a neovagina). After vaginoplasty, transfeminine people frequently experience gynecological concerns but their etiology is unknown due to a lack of knowledge of the neovaginal microenvironment. We characterized neovaginal microbiota and cytokines in 47 transfeminine participants. Participants self-reported sexual behaviors and symptoms, enabling correlation with bacterial (16S rRNA) and immune profiles. Four distinct clusters of co-occurring bacteria with unique immune profiles were identified. One cluster, which included Fastidiosipila , Ezakiella , and Murdochiella , was abundant, stable, and correlated with lower cytokines. Conversely, another cluster containing Howardella , Parvimonas , Fusobacterium , and Lawsonella was linked to higher cytokines. Although Lactobacillus was detected, Lactobacillus -dominance was rare. These findings underscore the need for evidence-based clinical guidelines tailored to transfeminine gynecologic care, emphasizing the vital role of the neovaginal microbiome in symptom management and sexual health.

Mushrooms in modern cosmetics: unlocking anti-aging, antioxidant, and therapeutic potential

Mushrooms have gained significant attention in the cosmetics industry due to their rich bioactive compounds with numerous skin benefits. This review explores the potential of various mushroom species as ingredients in cosmeceuticals, focusing on their anti-aging, anti-wrinkle, skin whitening, moisturizing, antioxidant, anti-inflammatory, and antimicrobial properties. Mushrooms such as Ganoderma lucidum, Lentinula edodes, Pleurotus ostreatus, and Agaricus bisporus have demonstrated the ability to inhibit key enzymes like elastase, tyrosinase, hyaluronidase, and collagenase, which play vital roles in skin aging and pigmentation. These bioactive compounds, including polysaccharides, phenolic acids, vitamins, and carotenoids, contribute to reduce wrinkles, improving skin hydration, enhancing elasticity, and providing protection from oxidative stress and UV damage. Furthermore, mushrooms have shown antimicrobial activities, making them effective against skin infections and inflammation. Mushrooms have become a popular ingredient in hair care products for their nourishing benefits, helping to promote healthy hair growth and protect against damage. As demand for natural, sustainable, and effective skincare alternatives rises, the incorporation of mushrooms into cosmetic formulations offers a promising solution. This review highlights the growing application of mushrooms in the development of innovative cosmeceuticals and emphasizes the need for further research to explore their full potential. Advancements in extraction techniques and the identification of new bioactive compounds are expected to enhance the efficacy of mushroom-based skincare products, making them an integral part of the global cosmetics market in the future.

Analysis of the Culturable Skin Microbiome of Horses from Southern Germany

Horses have close interactions with humans and are important as working animals and livestock. In contrast to smaller companion animals like cats and dogs, there is only little information available about their skin microbiome. The objective of this study was to identify and characterize the culturable cutaneous microbiome of healthy horses. Samples were taken from 14 horses from Southern Germany which were randomly enrolled in this study. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was used as a method to detect the culturable microorganisms of horse skin. The most abundant culturable species of horse skin identified in this study include Bacillus cereus, Bacillus pumilus, Carnobacterium inhibens, Exiguobacterium sibiricum, Macrococcus carouselicus, Macrococcus goetzii and Staphylococcus equorum. Analyses of the bacteria across different body regions indicated the specific preferences of species for certain skin areas. In addition, our data hinted to an influence of the age of the horses tested and an influence between the four stables studied.

Absolute quantification of the living skin microbiome overcomes relic-DNA bias and reveals specific patterns across volunteers

BACKGROUND

As the first line of defense against external pathogens, the skin and its resident microbiota are responsible for protection and eubiosis. Innovations in DNA sequencing have significantly increased our knowledge of the skin microbiome. However, current characterizations do not discriminate between DNA from live cells and remnant DNA from dead organisms (relic DNA), resulting in a combined readout of all microorganisms that were and are currently present on the skin rather than the actual living population of the microbiome. Additionally, most methods lack the capability for absolute quantification of the microbial load on the skin, complicating the extrapolation of clinically relevant information.

RESULTS

Here, we integrated relic-DNA depletion with shotgun metagenomics and bacterial load determination to quantify live bacterial cell abundances across different skin sites. Though we discovered up to 90% of microbial DNA from the skin to be relic DNA, we saw no significant effect of this on the relative abundances of taxa determined by shotgun sequencing. Relic-DNA depletion prior to sequencing strengthened underlying patterns between microbiomes across volunteers and reduced intraindividual similarity. We determined the absolute abundance and the fraction of population alive for several common skin taxa across body sites and found taxa-specific differential abundance of live bacteria across regions to be different from estimates generated by total DNA (live + dead) sequencing.

CONCLUSIONS

Our results reveal the significant bias relic DNA has on the quantification of low biomass samples like the skin. The reduced intraindividual similarity across samples following relic-DNA depletion highlights the bias introduced by traditional (total DNA) sequencing in diversity comparisons across samples. The divergent levels of cell viability measured across different skin sites, along with the inconsistencies in taxa differential abundance determined by total vs live cell DNA sequencing, suggest an important hypothesis for certain sites being susceptible to pathogen infection. Overall, our study demonstrates a characterization of the skin microbiome that overcomes relic-DNA bias to provide a baseline for live microbiota that will further improve mechanistic studies of infection, disease progression, and the design of therapies for the skin. Video Abstract.