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

Age-Related Variation of Bacterial and Fungal Communities in Different Body Habitats across the Young, Elderly, and Centenarians in Sardinia

Human body microbes interact with the host, forming microbial communities that are in continual flux during the aging process. Previous studies have mostly focused on surveying a single body habitat to determine the age-related variation in the bacterial and fungal communities. A more comprehensive understanding of the variation in the human microbiota and mycobiota across multiple body habitats related to aging is still unclear. To obtain an integrated view of the spatial distribution of microbes in a specific Mediterranean population across a wide age range, we surveyed the bacterial and fungal communities in the skin, oral cavity, and gut in the young, elderly, and centenarians in Sardinia using 16S rRNA gene and internal transcribed spacer 1 (ITS1) sequencing. We found that the distribution and correlation of bacterial and fungal communities in Sardinians were largely determined by body site. In each age group, the bacterial and fungal communities found in the skin were significantly different in structure. In the oral cavity, age had a marginal impact on the structures of the bacterial and fungal communities. Furthermore, the gut bacterial communities in centenarians clustered separately from those of the young and elderly, while the fungal communities in the gut habitat could not be separated by host age.IMPORTANCE Site-specific microbial communities are recognized as important factors in host health and disease. To better understand how the human microbiota potentially affects and is affected by its host during the aging process, the fundamental issue to address is the distribution of microbiota related to age. Here, we show an integrated view of the spatial distribution of microbes in a specific Mediterranean population (Sardinians) across a wide age range. Our study indicates that age plays a critical role in shaping the human microbiota in a habitat-dependent manner. The dynamic age-related microbiota changes we observed across multiple body sites may provide possibilities for modulating microbe communities to maintain or improve health during aging.

Vancomycin Is Protective in a Neonatal Mouse Model of Staphylococcus epidermidis-Potentiated Hypoxic-Ischemic Brain Injury

Infection is correlated with increased risk of neurodevelopmental sequelae in preterm infants. In modeling neonatal brain injury, Toll-like receptor agonists have often been used to mimic infections and induce inflammation. Using the most common cause of bacteremia in preterm infants, Staphylococcus epidermidis, we present a more clinically relevant neonatal mouse model that addresses the combined effects of bacterial infection together with subsequent hypoxic-ischemic brain insult. Currently, there is no neuroprotective treatment for the preterm population. Hence, we tested the neuroprotective effects of vancomycin with and without adjunct therapy using the anti-inflammatory agent pentoxifylline. We characterized the effects of S. epidermidis infection on the inflammatory response in the periphery and the brain, as well as the physiological changes in the central nervous system that might affect neurodevelopmental outcomes. Intraperitoneal injection of postnatal day 4 mice with a live clinical isolate of S. epidermidis led to bacteremia and induction of proinflammatory cytokines in the blood, as well as transient elevations of neutrophil and monocyte chemotactic cytokines and caspase 3 activity in the brain. When hypoxia-ischemia was induced postinfection, more severe brain damage was observed in infected animals than in saline-injected controls. This infection-induced inflammation and potentiated brain injury was inoculum dose dependent and was alleviated by the antibiotic vancomycin. Pentoxifylline did not provide any additional neuroprotective effect. Thus, we show for the first time that live S. epidermidis potentiates hypoxic-ischemic preterm brain injury and that peripheral inhibition of inflammation with antibiotics, such as vancomycin, reduces the extent of brain injury.

Host-Specific Evolutionary and Transmission Dynamics Shape the Functional Diversification of Staphylococcus epidermidis in Human Skin

Metagenomic inferences of bacterial strain diversity and infectious disease transmission studies largely assume a dominant, within-individual haplotype. We hypothesize that within-individual bacterial population diversity is critical for homeostasis of a healthy microbiome and infection risk. We characterized the evolutionary trajectory and functional distribution of Staphylococcus epidermidis-a keystone skin microbe and opportunistic pathogen. Analyzing 1,482 S. epidermidis genomes from 5 healthy individuals, we found that skin S. epidermidis isolates coalesce into multiple founder lineages rather than a single colonizer. Transmission events, natural selection, and pervasive horizontal gene transfer result in population admixture within skin sites and dissemination of antibiotic resistance genes within-individual. We provide experimental evidence for how admixture can modulate virulence and metabolism. Leveraging data on the contextual microbiome, we assess how interspecies interactions can shape genetic diversity and mobile gene elements. Our study provides insights into how within-individual evolution of human skin microbes shapes their functional diversification.

Antibiotic Delivery Strategies to Treat Skin Infections When Innate Antimicrobial Defense Fails

The epidermal skin barrier protects the body from a host of daily challenges, providing protection against mechanical insults and the absorption of chemicals and xenobiotics. In addition to the physical barrier, the epidermis also presents an innate defense against microbial overgrowth. This is achieved through the presence of a diverse collection of microorganisms on the skin (the "microbiota") that maintain a delicate balance with the host and play a significant role in overall human health. When the skin is wounded, the local tissue with a compromised barrier can become colonized and ultimately infected if bacterial growth overcomes the host response. Wound infections present an immense burden in healthcare costs and decreased quality of life for patients, and treatment becomes increasingly important because of the negative impact that infection has on slowing the rate of wound healing. In this review, we discuss specific challenges of treating wound infections and the advances in drug delivery platforms and formulations that are under development to improve topical delivery of antimicrobial treatments.

Staphylococcus epidermidis Contributes to Healthy Maturation of the Nasal Microbiome by Stimulating Antimicrobial Peptide Production

The composition of the human microbiome profoundly impacts human well-being. However, the mechanisms underlying microbiome maturation are poorly understood. The nasal microbiome is of particular importance as a source of many respiratory infections. Here, we performed a large sequencing and culture-based analysis of the human nasal microbiota from different age groups. We observed a significant decline of pathogenic bacteria before adulthood, with an increase of the commensal Staphylococcus epidermidis. In seniors, this effect was partially reversed. In vitro, many S. epidermidis isolates stimulated nasal epithelia to produce antimicrobial peptides, killing pathogenic competitors, while S. epidermidis itself proved highly resistant owing to its exceptional capacity to form biofilms. Furthermore, S. epidermidis isolates with high antimicrobial peptide-inducing and biofilm-forming capacities outcompeted pathogenic bacteria during nasal colonization in vivo. Our study identifies a pivotal role of S. epidermidis in healthy maturation of the nasal microbiome, which is achieved at least in part by symbiotic cooperation with innate host defense.

Revealing the secret life of skin - with the microbiome you never walk alone

The human skin microbiome has recently become a focus for both the dermatological and cosmetic fields. Understanding the skin microbiota, that is the collection of vital microorganisms living on our skin, and how to maintain its delicate balance is an essential step to gain insight into the mechanisms responsible for healthy skin and its appearance. Imbalances in the skin microbiota composition (dysbiosis) are associated with several skin conditions, either pathological such as eczema, acne, allergies or dandruff or non‐pathological such as sensitive skin, irritated skin or dry skin. Therefore, the development of approaches which preserve or restore the natural, individual balance of the microbiota represents a novel target not only for dermatologists but also for skincare applications. This review gives an overview on the current knowledge on the skin microbiome, the currently available sampling and analysis techniques as well as a description of current approaches undertaken in the skincare segment to help restoring and balancing the structure and functionality of the skin microbiota.

The Skin and Intestinal Microbiota and Their Specific Innate Immune Systems

The skin and intestine are active organs of the immune system that are constantly exposed to the outside environment. They support diverse microbiota, both commensal and pathogenic, which encompass bacteria, viruses, fungi, and parasites. The skin and intestine must maintain homeostasis with the diversity of commensal organisms present on epithelial surfaces. Here we review the current literature pertaining to epithelial barrier formation, microbial composition, and the complex regulatory mechanisms governing the interaction between the innate immune system and microbiota in the skin and intestine. We also compare and contrast the skin and intestine—two different organ systems responsible creating a protective barrier against the external environment, each of which has unique mechanisms for interaction with commensal populations and host repair.

The role of bacterial skin infections in atopic dermatitis: expert statement and review from the International Eczema Council Skin Infection Group

Patients with atopic dermatitis (AD) have an increased risk of bacterial skin infections, which cause significant morbidity and, if untreated, may become systemic. Staphylococcus aureus colonizes the skin of most patients with AD and is the most common organism to cause infections. Overt bacterial infection is easily recognized by the appearance of weeping lesions, honey‐coloured crusts and pustules. However, the wide variability in clinical presentation of bacterial infection in AD and the inherent features of AD – cutaneous erythema and warmth, oozing associated with oedema, and regional lymphadenopathy – overlap with those of infection, making clinical diagnosis challenging. Furthermore, some features may be masked because of anatomical site‐ and skin‐type‐specific features, and the high frequency of S. aureus colonization in AD makes positive skin swab culture of suspected infection unreliable as a diagnostic tool. The host mechanisms and microbial virulence factors that underlie S. aureus colonization and infection in AD are incompletely understood. The aim of this article is to present the latest evidence from animal and human studies, including recent microbiome research, to define the clinical features of bacterial infections in AD, and to summarize our current understanding of the host and bacterial factors that influence microbial colonization and virulence.

Microbial interactions in the atopic march

The human body is populated by a large number of microorganisms and exist in symbiosis with these immensely diverse communities, which are suggested to influence health and disease. The microbiota plays an essential role in the maturation and function of the immune system. The prevalence of atopic diseases has increased drastically over the past decades, and the co-occurrence of multiple allergic diseases and allergic sensitization starting in early life has gained a great deal of attention. Immune responses in different organs affected by allergic diseases (e.g. skin, intestine and lung) may be linked to microbial changes in peripheral tissues. In the current review, we provide an overview of the current understanding of microbial interactions in allergic diseases and their potential role in the atopic march.

Insights into atopic dermatitis gained from genetically defined mouse models

Atopic dermatitis (AD) is characterized by severe pruritus and recurrent eczema with a chronic disease course. Impaired skin barrier function, hyperactivated T_H2 cell-type inflammation, and pruritus-induced scratching contribute to the disease pathogenesis of AD. Skin microbial alterations complicate the pathogenesis of AD further. Mouse models are a powerful tool to analyze such intricate pathophysiology of AD, with a caution that anatomy and immunology of the skin differ between human subjects and mice. Here we review recent understanding of AD etiology obtained using mouse models, which address the epidermal barrier, skin microbiome, T_H2 immune response, and pruritus.

[Oral manifestations of KID syndrome: rare clinical case]

The paper presents a rare clinical case of an infant with KID (Keratitis, Ichthyosis, Deafness) syndrome (about 100 patients reported so far) admitted for histological verification of oral mucosa lesions. Disease pathogenesis defines inadequate reparation and skin and mucosa innate immunity defect leading to higher incidence of bacterial and fungal infections, so the 4-years old girl received treatment for vegetating candidiasis of the oral mucosa for several weeks with no clinical improvement. Initial examination showed that the oral lesions resulted from sharp edges of severely affected carious teeth. Histological study of multifocal biopsy revealed pyogenic granulomas and no signs of SCC. Teeth extraction and symptomatic treatment leaded to significant clinical improvement and some remained mucosal changes may be attributed to syndrome manifestations.

Staphylococcus aureus and the Cutaneous Microbiota Biofilms in the Pathogenesis of Atopic Dermatitis

Biofilm is the dominant mode of growth of the skin microbiota, which promotes adhesion and persistence in the cutaneous microenvironment, thus contributing to the epidermal barrier function and local immune modulation. In turn, the local immune microenvironment plays a part in shaping the skin microbiota composition. Atopic dermatitis (AD) is an immune disorder characterized by a marked dysbiosis, with a sharp decline of microbial diversity. During AD flares biofilm-growing Staphylococcus aureus emerges as the major colonizer in the skin lesions, in strict association with disease severity. The chronic production of inflammatory cytokines in the skin of AD individuals concurs at supporting S. aureus biofilm overgrowth at the expense of other microbial commensals, subverting the composition of the healthy skin microbiome. The close relationship between the host and microbial biofilm resident in the skin has profound implications on human health, making skin microbiota an attractive target for the therapeutic management of different skin disorders.

[Role of the microbiome in chronic wounds]

BACKGROUND

The microbiome, collective microbial life in defined areas of the body, is of great importance.

OBJECTIVE

What is the significance of the wound microbiome in the treatment of chronic wounds? Which interactions exist with other microbiomes and which conclusions can be drawn for wound management?

MATERIALS AND METHODS

Swabs or debridement samples from wounds were analysed for microbial growth by culture or gene-based techniques. The genetic results are used to determine the wound microbiome. The pathogens were evaluated according to proportion of different species and related to different factors like type and location of wound, disease and underlying illnesses and to define the wound microbiome.

RESULTS

In comparison with conventional microbiological detection methods the wound microbiome comprises many more types and quantities of species. The wound microbiome is related to skin microbiome showing complex and time-dependent composition, as well as inter- and intraindividual differences. Diabetic wounds exhibit disease-related changes, e.g. staphylococcal species dominate whereas streptococcal species dominate in nondiabetic wounds.

CONCLUSIONS

The analysis of wound microbiome is still at an early stage; however it has already been shown that in hemodynamic disorders there are disease-specific relationships with the wound microbiome, which can also provide clues about the course of the disease. Phenomena from the skin microbiome should also be effective in wounds. In this context modern antimicrobial treatment options beyond conventional chemotherapy like colonization modulation become possible.

Changing our microbiome: probiotics in dermatology

BACKGROUND

Commensal bacteria are a major factor in human health and disease pathogenesis. Interest has recently expanded beyond the gastrointestinal microbiome to include the skin microbiome and its impact on various skin diseases.

OBJECTIVES

Here we present current data reviewing the role of the microbiome in dermatology, considering both the gut and skin microflora. Our objective was to evaluate whether the clinical data support the utility of oral and topical probiotics for certain dermatological diseases.

METHODS

The PubMed and ClinicalTrials.gov databases were searched for basic science, translational research and clinical studies that investigated differences in the cutaneous microbiome and the impact of probiotics in patients with atopic dermatitis, acne vulgaris, psoriasis, chronic wounds, seborrhoeic dermatitis and cutaneous neoplasms.

RESULTS

Few clinical trials exist that explore the utility of probiotics for the prevention and treatment of dermatological diseases, with the exception of atopic dermatitis. Most studies investigated oral probiotic interventions, and of those utilizing topical probiotics, few included skin commensals. In general, the available clinical trials yielded positive results with improvement of the skin conditions after probiotic intervention.

CONCLUSIONS

Oral and topical probiotics appear to be effective for the treatment of certain inflammatory skin diseases and demonstrate a promising role in wound healing and skin cancer. However, more studies are needed to confirm these results. What's already known about this topic? The microbiome plays a role in human health and disease pathogenesis. Probiotics can manipulate the host microbiome and may confer health benefits for patients. Research to date has already begun to explore the utility of oral and topical probiotics for certain dermatological diseases. What does this study add? This review presents basic science and clinical trial data to support the role of the gut and skin microbiome in dermatology. Current data are reviewed on the use of probiotics in the prevention and treatment of skin diseases, including atopic dermatitis, acne vulgaris, psoriasis, seborrhoeic dermatitis, chronic wounds and cutaneous neoplasms. Future probiotic interventions are proposed.

Protective effect of inactivated blastoconidia in keratinocytes and human reconstituted epithelium against C. albicans infection

Candida albicans is commensal yeast that colonizes skin and mucosa; however, it can become an opportunist pathogen by changing from blastoconidia (commensal form) into hypha (pathogenic form). Each form activates a different cytokines response in epithelial cells. Little is known about the commensal role of C. albicans in the innate immunity. This work studied whether stimulation with C. albicans blastoconidia induces protection in keratinocytes and/or in a reconstituted human epithelium (RHE) infected with C. albicans. For this, inactivated C. albicans blastoconidia was used to stimulate keratinocytes and RHE prior to infection with C. albicans. Blastoconidia induced different cytokine expression profiles; in the case of RHE it decreased interleukin (IL)-1β and IL-10 and increased IL-8, tumor necrosis factor α (TNF-α), and interferon γ (IFN-γ). A significant increase in the expression of human β-defensins (HBD) 2 and HBD3 was observed in blastoconidia stimulated keratinocytes and RHE, associated with impaired growth and viability of C. albicans. Additionally, blastoconidia stimulation decreased the expression of virulence factors in C. albicans that are associated with filamentation (EFG1, CPH1 and NRG1), adhesion (ALS5), and invasion (SAP2). Blastoconidia stimulated RHE was significantly less damaged by C. albicans invasion. These results show that the commensal form of C. albicans would exert a protective effect against self-infection.

Staphylococcus epidermidis: A Potential New Player in the Physiopathology of Acne?

Background: Cutibacterium acnes has been identified as one of the main triggers of acne. However, increasing knowledge of the human skin microbiome raises questions about the role of other skin commensals, such as Staphylococcus epidermidis, in the physiopathology of this skin disease. Summary: This review provides an overview of current knowledge of the potential role of S. epidermidis in the physiopathology of acne. Recent research indicates that acne might be the result of an unbalanced equilibrium between C. acnes and S. epidermidis,according to dedicated interactions. Current treatments act on C. acnesonly. Other treatment options may be considered, such as probiotics derived from S. epidermidis to restore the naturally balanced microbiota or through targeting the regulation of the host’s AMP mediators. Key Messages: Research seems to confirm the beneficial role of S. epidermidis in acne by limiting C. acnes over-colonisation and inflammation.

Association of Disease Severity With Skin Microbiome and Filaggrin Gene Mutations in Adult Atopic Dermatitis

Importance

Skin microbiome correlates with disease severity for lesional and nonlesional skin, indicating a global influence of atopic dermatitis (AD). A relation between skin microbiome and filaggrin gene (FLG) mutations proposes a possible association between skin microbiome and host genetics.

Objectives

To assess skin and nasal microbiome diversity and composition in patients with AD and compare with healthy controls, and to investigate the microbiome in relation to disease severity and FLG mutations in patients with AD.

Design, Setting, and Participants

An observational case-control study of 45 adult healthy controls and 56 adult patients with AD was carried out from January 2015 to June 2015 in a tertiary referral center, Department of Dermatology, Bispebjerg Hospital, Denmark.

Exposures

Bacterial swabs were taken from patients with AD (lesional skin, nonlesional skin, and anterior nares) and from healthy controls (nonlesional skin and anterior nares). Eczema severity was assessed and FLG mutations noted. Bacterial DNA was extracted from swabs, and V3-V4 16S rDNA regions amplified with PCR. Samples were analyzed at Statens Serum Institut September 2015 to September 2016. Bioinformatics analyses of the microbiome were analyzed using R statistical software (version 3.3.1, R Foundation Inc).

Main Outcomes and Measures

Skin microbiomes were investigated using next-generation sequencing targeting 16S ribosomal RNA.

Results

Microbiome alpha diversity was lower in patients with AD compared with healthy controls in nonlesional skin (effect size, 0.710; 95% CI, 0.27-1.15; P = .002), lesional skin (effect size, 0.728; 95% CI, 0.35-1.33; P = .001), and nose (effect size, 1.111; 95% CI, 0.48-0.94; P < .001). Alpha diversity was inversely correlated with disease severity for lesional (effect size, 0.530; 95% CI, 0.23-1.64; P = .02) and nonlesional skin (effect size, 0.451; 95% CI, 0.04-2.44; P = .04) in patients with AD. Microbiome composition in AD nonlesional skin was linked to FLG mutations.

Conclusions and Relevance

An altered microbiome composition in patients with AD in nonlesional skin, lesional skin, as well as nose, suggests a global influence of AD. Microbiome composition in AD nonlesional skin is associated with FLG mutations, proposing a possible association between the skin microbiome and host genetics.

Microbiome in the hair follicle of androgenetic alopecia patients

Androgenetic alopecia is the most common form of hair loss in males. It is a multifactorial condition involving genetic predisposition and hormonal changes. The role of microflora during hair loss remains to be understood. We therefore analyzed the microbiome of hair follicles from hair loss patients and the healthy. Hair follicles were extracted from occipital and vertex region of hair loss patients and healthy volunteers and further dissected into middle and lower compartments. The microbiome was then characterized by 16S rRNA sequencing. Distinct microbial population were found in the middle and lower compartment of hair follicles. Middle hair compartment was predominated by Burkholderia spp. and less diverse; while higher bacterial diversity was observed in the lower hair portion. Occipital and vertex hair follicles did not show significant differences. In hair loss patients, miniaturized vertex hair houses elevated Propionibacterium acnes in the middle and lower compartments while non-miniaturized hair of other regions were comparable to the healthy. Increased abundance of P. acnes in miniaturized hair follicles could be associated to elevated immune response gene expression in the hair follicle.

Scalp bacterial shift in Alopecia areata

The role of microbial dysbiosis in scalp disease has been recently hypothesized. However, little information is available with regards to the association between microbial population on the scalp and hair diseases related to hair growth. Here we investigated bacterial communities in healthy and Alopecia areata (AA) subjects. The analysis of bacterial distribution at the genus level highlighted an increase of Propionibacterium in AA subjects alongside a general decrease of Staphylococcus. Analysis of log Relative abundance of main bacterial species inhabiting the scalp showed a significant increase of Propionibacterium acnes in AA subjects compared to control ones. AA scalp condition is also associated with a significant decrease of Staphylococcus epidermidis relative abundance. No significant changes were found for Staphylococcus aureus. Therefore, data from sequencing profiling of the bacterial population strongly support a different microbial composition of the different area surrounded hair follicle from the epidermis to hypodermis, highlighting differences between normal and AA affected the scalp. Our results highlight, for the first time, the presence of a microbial shift on the scalp of patients suffering from AA and gives the basis for a larger and more complete study of microbial population involvement in hair disorders.

Tokiinshi, a traditional Japanese medicine (Kampo), suppresses Panton-Valentine leukocidin production in the methicillin-resistant Staphylococcus aureus USA300 clone

It is necessary to develop agents other than antimicrobials for the treatment of Staphylococcus aureus infections to prevent the emergence of antimicrobial-resistant strains. Particularly, anti-virulence agents against the Panton-Valentine leukocidin (PVL)-positive methicillin-resistant S. aureus (MRSA), USA300 clone, is desired due to its high pathogenicity. Here, we investigated the potential anti-virulence effect of Tokiinshi, which is a traditional Japanese medicine (Kampo) used for skin diseases, against the USA300 clone. A growth inhibition assay showed that a conventional dose (20 mg/ml) of Tokiinshi has bactericidal effects against the clinical USA300 clones. Notably, the growth inhibition effects of Tokiinshi against S. epidermidis strains, which are the major constituents of the skin microbiome, was a bacteriostatic effect. The data suggested that Tokiinshi is unlikely to affect skin flora of S. epidermidis. Furthermore, PVL production and the expression of its gene were significantly suppressed in the USA300 clone by a lower concentration (5 mg/ml) of Tokiinshi. This did not affect the number of viable bacteria. Moreover, Tokiinshi significantly suppressed the expression of the agrA gene, which regulates PVL gene expression. For the first time, our findings strongly suggest that Tokiinshi has the potential to attenuate the virulence of the USA300 clone by suppressing PVL production via agrA gene suppression.

Commensal Staphylococci Influence Staphylococcus aureus Skin Colonization and Disease

Commensal organisms that constitute the skin microbiota play a pivotal role in the orchestration of cutaneous homeostasis and immune competence. This balance can be promptly offset by the expansion of the opportunistic pathogen Staphylococcus aureus, which is responsible for the majority of bacterial skin infections. S. aureus carriage is also known to be a precondition for its transmission and pathogenesis. Recent reports suggest that skin-dwelling coagulase-negative staphylococci (CoNS) can prime the skin immune system to limit the colonization potential of invaders, and they can directly compete through production of antimicrobial molecules or through signaling antagonism. We review recent advances in these CoNS colonization resistance mechanisms, which may serve to aid development of pharmacologic and probiotic intervention strategies to limit S. aureus skin colonization and disease.

Microbiome Imbalances: An Overlooked Potential Mechanism in Chronic Nonhealing Wounds

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

Pathophysiology of atopic dermatitis: Clinical implications

Atopic dermatitis (AD) is the most common chronic inflammatory skin disease. Genetic predisposition, epidermal barrier disruption, and dysregulation of the immune system are some of the critical components of AD. An impaired skin barrier may be the initial step in the development of the atopic march as well as AD, which leads to further skin inflammation and allergic sensitization. Type 2 cytokines as well as interleukin 17 and interleukin 22 contribute to skin barrier dysfunction and the development of AD. New insights into the pathophysiology of AD have focused on epidermal lipid profiles, neuroimmune interactions, and microbial dysbiosis. Newer therapeutic strategies focus on improving skin barrier function and targeting polarized immune pathways found in AD. Further understanding of AD pathophysiology will allow us to achieve a more precision medicine approach to the prevention and the treatment of AD.

Influences on allergic mechanisms through gut, lung, and skin microbiome exposures

In industrialized societies the incidence of allergic diseases like atopic dermatitis, food allergies, and asthma has risen alarmingly over the last few decades. This increase has been attributed, in part, to lifestyle changes that alter the composition and function of the microbes that colonize the skin and mucosal surfaces. Strategies that reverse these changes to establish and maintain a healthy microbiome show promise for the prevention and treatment of allergic disease. In this Review, we will discuss evidence from preclinical and clinical studies that gives insights into how the microbiota of skin, intestinal tract, and airways influence immune responses in the context of allergic sensitization.

Interactions between Host Immunity and Skin-Colonizing Staphylococci: No Two Siblings Are Alike

As the outermost layer of the body, the skin harbors innumerable and varied microorganisms. These microorganisms interact with the host, and these interactions contribute to host immunity. One of the most abundant genera of skin commensals is Staphylococcus. Bacteria belonging to this genus are some of the most influential commensals that reside on the skin. For example, colonization by Staphylococcus aureus, a well-known pathogen, increases inflammatory responses within the skin. Conversely, colonization by Staphylococcus epidermis, a coagulase-negative staphylococcal species that are prevalent throughout the skin, can be innocuous or beneficial. Thus, manipulating the abundance of these two bacterial species likely alters the skin microbiome and modulates the cutaneous immune response, with potential implications for various inflammation-associated skin diseases. Importantly, before researchers can begin manipulating the skin microbiome to prevent and treat disease, they must first fully understand how these two species can modulate the cutaneous immune response. In this review, we discuss the nature of the interactions between these two bacterial species and immune cells within the skin, discussing their immunogenicity within the context of skin disorders.

Staphylococcus aureus: an underestimated factor in the pathogenesis of atopic dermatitis?

Atopic dermatitis is a common, recurrent pruritic dermatosis with a complex pathogenesis. It has been associated with disordered patterns of immunological response and impaired epithelial barrier integrity. These features predispose the patients to robust colonization of skin lesions by Staphylococcus aureus. Virulence factors of S. aureus (e.g. superantigens, α- and δ-toxin, protein A) have been shown to exacerbate and perpetuate the course of atopic dermatitis. Novel therapeutic options with potential for restoring natural microbiome composition are being elaborated and may enter clinical practice in the future.

The microbiome and immunodeficiencies: Lessons from rare diseases

Primary immunodeficiencies (PIDs) are inherited disorders of the immune system, associated with a considerable increase in susceptibility to infections. PIDs can also predispose to malignancy, inflammation and autoimmunity. There is increasing awareness that some aspects of the immune dysregulation in PIDs may be linked to intestinal microbiota. Indeed, the gut microbiota and its metabolites have been shown to influence immune functions and immune homeostasis both locally and systemically. Recent studies have indicated that genetic defects causing PIDs lead to perturbations in the conventional mechanisms underlying homeostasis in the gut, resulting in poor immune surveillance at the intestinal barrier, which associates with altered intestinal permeability and bacterial translocation. Consistently, a substantial proportion of PID patients presents with clinically challenging IBD-like pathology. Here, we describe the current body of literature reporting on dysbiosis of the gut microbiota in different PIDs and how this can be either the result or cause of immune dysregulation. Further, we report how infections in PIDs enhance pathobionts colonization and speculate how, in turn, pathobionts may be responsible for increased disease susceptibility and secondary infections in these patients. The potential relationship between the microbial composition in the intestine and other sites, such as the oral cavity and skin, is also highlighted. Finally, we provide evidence, in preclinical models of PIDs, for the efficacy of microbiota manipulation to ameliorate disease complications, and suggest that the potential use of dietary intervention to correct dysbiotic flora in PID patients may hold promise.

Reconstructed Human Epidermis Predicts Barrier-Improving Effects of Lactococcus lactis Emulsion in Humans

BACKGROUND/AIMS

The skin provides protection against chemical, physical, and biological stressors, yet the skin morphology changes over the course of life. These changes might affect the skin barrier function and facilitate the onset of age-related diseases. Since orally applied lactic acid bacteria ameliorate signs of aged and atopic skin, we investigated the effects of a topically applied Lactococcus lactis emulsion.

METHODS

In a blinded, randomized, vehicle-controlled trial, we studied topical Lactococcus effects both in vitro and in 20 healthy female volunteers. Commercially available reconstructed human epidermis (RHE) was treated for 4 days (once daily) and volar forearms were treated for 30 days (twice daily).

RESULTS

Lactococcus formulations improve the skin barrier in RHE as shown by increased filaggrin and human β-defensin-2 expression as well as by the 23% declined mean apparent permeability coefficients for caffeine. A reduction of 18% in transepidermal water loss confirms this effect in humans. Moreover, Lactococcus emulsion optimized skin hydration and surface pH. Skin irritation was not detected.

CONCLUSIONS

Lactococcus emulsion improved the skin barrier function with good biocompatibility. Moreover, our study exemplifies the translational predictive capacity of testing on RHE with respect to Lactococcus emulsion.

The microbiome in patients with atopic dermatitis

As an interface with the environment, the skin is a complex ecosystem colonized by many microorganisms that coexist in an established balance. The cutaneous microbiome inhibits colonization with pathogens, such as Staphylococcus aureus, and is a crucial component for function of the epidermal barrier. Moreover, crosstalk between commensals and the immune system is now recognized because microorganisms can modulate both innate and adaptive immune responses. Host-commensal interactions also have an effect on the developing immune system in infants and, subsequently, the occurrence of diseases, such as asthma and atopic dermatitis (AD). Later in life, the cutaneous microbiome contributes to the development and course of skin disease. Accordingly, in patients with AD, a decrease in microbiome diversity correlates with disease severity and increased colonization with pathogenic bacteria, such as S aureus. Early clinical studies suggest that topical application of commensal organisms (eg, Staphylococcus hominis or Roseomonas mucosa) reduces AD severity, which supports an important role for commensals in decreasing S aureus colonization in patients with AD. Advancing knowledge of the cutaneous microbiome and its function in modulating the course of skin disorders, such as AD, might result in novel therapeutic strategies.

Langerhans and inflammatory dendritic epidermal cells in atopic dermatitis are tolerized toward TLR2 activation

BACKGROUND

The skin of atopic dermatitis (AD) patients presents a significant dysbalance of the microbiome with a high colonization by Staphylococcus aureus (S. aureus), which positively correlates with the severity of the disease.

OBJECTIVE

Understanding the role of epidermal dendritic cells (DC) as link between the innate and the adaptive immune systems in AD.

METHODS

Comparative phenotypic and functional analysis of TLR2 on Langerhans cells (LC) and inflammatory dendritic epidermal cells (IDEC) in organotypic models as well as freshly isolated cells from healthy and AD skin.

RESULTS

In situ analysis of freshly isolated LC and IDEC from AD skin revealed decreased TLR2 expression compared to LC from healthy skin. In contrast to IDEC, LC from AD skin failed to display any evidence for in situ activation. Exposure to TLR2 ligand Pam3Cys resulted in maturation and increased migratory activity of LC from normal skin. LC and IDEC from AD were unresponsive to TLR2 ligand in that they failed to mature and displayed a high spontaneous migratory activity. Keratinocytes from both healthy and AD skin expressed similar levels of TLR2. The production of IL-6 and IL-10 was impaired by Pam3Cys in supernatants from AD skin. IL-18 was significantly higher in supernatants from AD skin and not influenced by TLR2 ligation, when compared to healthy skin.

CONCLUSION

Our results suggest that TLR2-mediated sensing of S. aureus-derived signals is strongly impaired in LC from AD skin. This phenomenon may partly contribute to the immune deviation in AD and the lack of S. aureus clearance.

Topical nicotinic receptor activation improves wound bacterial infection outcomes and TLR2-mediated inflammation in diabetic mouse wounds

The cholinergic anti-inflammatory pathway can directly affect skin antibacterial responses via nicotinic acetylcholine receptors (nAChRs). In particular, α7 nAChR (CHRNA7) present in the epidermis modulates the host response to wounding and/or wound bacterial infection. While physiologic inflammation is required to initiate normal wound repair and can be triggered by Toll-like receptor (TLR) activation, chronic inflammation is frequently observed in diabetic wounds and can occur, in part, via excessive TLR2 activation or production. Consequently, this can delay physiologic wound healing responses and increase diabetic host susceptibility to bacterial infection. In this study, we demonstrate that topical nAChR activation diminishes bacterial survival and systemic dissemination in a mouse model of diabetic wound infection, while reducing wound TLR2 production, relative to control mice. We further determined that the antimicrobial peptide activity of diabetic mouse wounds is increased compared to control mice, but this effect is lost following topical nAChR activation. Finally, we observed that human diabetic wounds exhibit impaired α7 nAChR (CHRNA7) abundance and localization relative to human control (nondiabetic) skin. These findings suggest that topical administration of nAChR agonists may improve wound healing and infection outcomes in diabetic wounds by dampening TLR2-mediated inflammation and antimicrobial peptide response, and that the diabetic microenvironment may promote aberrant CHRNA7 production/activation that likely contributes to diabetic wound pathogenesis.

Effects of Lactobacillus reuteri LR1 on the growth performance, intestinal morphology, and intestinal barrier function in weaned pigs

The objective of this study was to investigate the effects of Lactobacillus reuteri LR1, a new strain isolated from the feces of weaned pigs, on the growth performance, intestinal morphology, immune responses, and intestinal barrier function in weaned pigs. A total of 144 weaned pigs (Duroc × Landrace × Yorkshire, 21 d of age) with an initial BW of 6.49 ± 0.02 kg were randomly assigned to 3 dietary treatments with 8 replicate pens, each of per treatment and 6 pigs. Pigs were fed a basal diet (CON, controls), the basal diet supplemented with 100 mg/kg olaquindox and 75 mg/kg aureomycin (OA) or the basal diet supplemented with 5 × 1010 cfu/kg L. reuteri LR1 for a 14-d period. At the end of study, the ADG, ADFI, and G:F were calculated, and 1 randomly selected pig from each pen was euthanized for sample collection. The LR1 increased ADG (22.73%, P < 0.05) compared with CON. The villus height of the ileum was increased (P < 0.05) and crypt depth in duodenum was reduced (P < 0.05), along with increased (P < 0.05) villus height to crypt depth ratio of the jejunum and ileum by LR1 compared with CON and OA. LR1 increased (P < 0.05) ileal mucosal content of IL-22 and transforming growth factor-β compared with OA. Compared with CON, LR1 increased (P < 0.05) and OA decreased (P < 0.05) the ileal content of secretory immunoglobulin A (sIgA), and the abundance of transcripts of porcine β-defensin 2 and protegrin 1-5. Compared with CON, LR1 increased (P < 0.05) tight junction protein zonula occludens-1 and occludin transcripts in the mucosa of the jejunum and ileum, and those of mucin-2 in ileal mucosa. The relative expression of toll-like receptor 2 (TLR2) and TLR4 were increased (P < 0.05) in ileal mucosa in pigs fed LR1 compared with CON. In conclusion, these data indicated that dietary LR1 supplementation at 5 × 1010 cfu/kg improved growth performance, intestinal morphology, and intestinal barrier function in weaned pigs.

Survival of Staphylococcus epidermidis in Fibroblasts and Osteoblasts

Staphylococcus epidermidis is a leading cause of infections associated with indwelling medical devices, including prosthetic joint infection. While biofilm formation is assumed to be the main mechanism underlying the chronic infections S. epidermidis causes, we hypothesized that S. epidermidis also evades immune killing, contributing to its pathogenesis. Here, we show that prosthetic joint-associated S. epidermidis isolates can persist intracellularly within human fibroblasts and inside human and mouse osteoblasts. We also show that the intracellularly persisting bacteria reside primarily within acidic phagolysosomes and that over the course of infection, small-colony variants are selected for. Moreover, upon eukaryotic cell death, these bacteria, which can outlive their host, can escape into the extracellular environment, providing them an opportunity to form biofilms on implant surfaces at delayed time points in implant-associated infection. In summary, the acidic phagolysosomes of fibroblasts and osteoblasts serve as reservoirs for chronic or delayed S. epidermidis infection.

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

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

Toward Immunocompetent 3D Skin Models

3D human skin models provide a platform for toxicity testing, biomaterials evaluation, and investigation of fundamental biological processes. However, the majority of current in vitro models lack an inflammatory system, vasculature, and other characteristics of native skin, indicating scope for more physiologically complex models. Looking at the immune system, there are a variety of cells that could be integrated to create novel skin models, but to do this effectively it is also necessary to understand the interface between skin biology and tissue engineering as well as the different roles the immune system plays in specific health and disease states. Here, a progress report on skin immunity and current immunocompetent skin models with a focus on construction methods is presented; scaffold and cell choice as well as the requirements of physiologically relevant models are elaborated. The wide range of technological and fundamental challenges that need to be addressed to successfully generate immunocompetent skin models and the steps currently being made globally by researchers as they develop new models are explored. Induced pluripotent stem cells, microfluidic platforms to control the model environment, and new real-time monitoring techniques capable of probing biochemical processes within the models are discussed.

Cutaneous Burn Injury Promotes Shifts in the Bacterial Microbiome in Autologous Donor Skin: Implications for Skin Grafting Outcomes

INTRODUCTION

The cutaneous microbiome maintains skin barrier function, regulates inflammation, and stimulates wound-healing responses. Burn injury promotes an excessive activation of the cutaneous and systemic immune response directed against commensal and invading pathogens. Skin grafting is the primary method of reconstructing full-thickness burns, and wound infection continues to be a significant complication.

METHODS

In this study, the cutaneous bacterial microbiome was evaluated and subsequently compared to patient outcomes. Three different full-thickness skin specimens were assessed: control skin from non-burned subjects; burn margin from burn patients; and autologous donor skin from the same cohort of burn patients.

RESULTS

We observed that skin bacterial community structure of burn patients was significantly altered compared with control patients. We determined that the unburned autologous donor skin from burn patients exhibits a microbiome similar to that of the burn margin, rather than unburned controls, and that changes in the cutaneous microbiome statistically correlate with several post-burn complications. We established that Corynebacterium positively correlated with burn wound infection, while Staphylococcus and Propionibacterium negatively correlated with burn wound infection. Both Corynebacterium and Enterococcus negatively correlated with the development of sepsis.

CONCLUSIONS

This study identifies distinct differences in the cutaneous microbiome between burn subjects and unburned controls, and ascertains that select bacterial taxa significantly correlate with several comorbid complications of burn injury. These preliminary data suggest that grafting donor skin exhibiting bacterial dysbiosis may augment infection and/or graft failure and sets the foundation for more in-depth and mechanistic analyses in presumably "healthy" donor skin from patients requiring skin grafting procedures.

How human microbiome talks to health and disease

Microbes are ubiquitous in the human body. They usually live in communities, and each of these communities has a distinct taxonomical structure. Due to its close relationship with human health and disease, the human microbiome has received great attention and is probably considered to be the most valuable biomarker in preventing and solving human diseases. In this paper, we first review the value of the human microbiome. Then, we focus on the role of the human microbiome in influencing human health and disease. Furthermore, we intensively discuss the relationship between intestinal microbiota and cancer therapy. Finally, we briefly summarize the significance of the human microbiome based on the development of sequencing and bioinformatic techniques.

An approach on the potential use of probiotics in the treatment of skin conditions: acne and atopic dermatitis

Acne and Atopic Dermatitis (AD) are chronic inflammatory skin conditions with severe impact on a patient's life. Current treatments are related to adverse effects and do not represent a definitive cure. The present paper reviews the alterations in skin microbiome, specifically in acne and AD, and aims in searching for potential treatments based on benefic microorganisms, called probiotics. The review was made through bibliographic search of the main databases (Science Direct, PubMed, Scielo, Medline) between September 2015 and June 2016. Acne lesions create an environment that facilitates the excess growth of Propionibacterium acnes (P. acnes). AD is related to an increase in the proportion of Staphylococcus aureus (S. aureus) during flare-ups. Some microorganisms have been shown to act not only in the prevention but also in the competition for pathogenic microorganisms and beneficially affect the inflammatory process present in these conditions. Despite the high variety of tested bacteria, Staphylococcus, Streptococcus, Lactococcus, Lactobacillus, and Enterococcus are the ones which showed the highest potential to control acne, and Vitreoscilla filiformis (V. filiformis), Staphylococcus epidermidis (S. epidermidis), and species of Lactobacillus and Bifidobacterium in the treatment of AD. Many of these studies were in vitro, and more detailed research should be performed in order to prove the real efficacy and safety of probiotics in these situations. An interesting alternative seems to be the use of Bacteriocin-like inhibitory substances produced by probiotics, responsible for their antimicrobial activity.

Skin microbiota and human 3D skin models

Although the role of the microbiota in skin homeostasis is still emerging, there is growing evidence that an intact microbiota supports the skin barrier. The increasing number of research efforts that are trying to shed more light on the human skin-microbiota interaction requires the use of suitable experimental models. Three-dimensional (3D) skin equivalents have been established as a valuable tool in dermatological research because they contain a fully differentiated epidermal barrier that reflects the morphological and molecular characteristics of normal human epidermis. In this review, we provide an overview of current 3D skin models and illustrate the potential of 3D skin models to study the human skin-microbiota interplay.