Fermentation of Propionibacterium acnes, a commensal bacterium in the human skin microbiome, as skin probiotics against methicillin-resistant Staphylococcus aureus

Cutibacterium adaptation to life on humans provides a novel biomarker of C. acnes infections

The domestication of cattle provided Propionibacteriaceae the opportunity to adapt to human skin. These bacteria constitute a distinct genus ( Cutibacterium ), and a single species within that genus ( C. acnes ) dominates 25% of human skin. C. acnes protects humans from pathogen colonization, but it can also infect indwelling medical devices inserted through human skin. Proteins that help Cutibacteria live on our skin may also act as virulence factors during an opportunistic infection, like a shoulder periprosthetic joint infection (PJI). To better understand the evolution of this commensal and opportunistic pathogen, we sought to extensively characterize one of these proteins, RoxP. This secreted protein is only found in the Cutibacterium genus, helps C. acnes grow in oxic environments, and is required for C. acnes to colonize human skin. Structure-based sequence analysis of twenty-one RoxP orthologs (71-100% identity to C. acnes strain KPA171202 RoxP_1) revealed a high-degree of molecular surface conservation and helped identify a potential heme-binding interface. Biophysical evaluation of a subset of seven RoxP orthologs (71-100% identity) demonstrated that heme-binding is conserved. Computational modeling of these orthologs suggests that RoxP heme-binding is mediated by an invariant molecular surface composed of a surface-exposed tryptophan (W66), adjacent cationic pocket, and nearby potential heme axial ligands. Further, these orthologs were found to undergo heme-dependent oligomerization. To further probe the role of this protein in C. acnes biology, we developed four monoclonal anti-RoxP antibodies, assessed the binding of those antibodies to a subset of ten RoxP orthologs (71-100% identity), developed an anti-RoxP sandwich ELISA (sELISA) with sub-nanogram sensitivity, and adapted that sELISA to quantitate RoxP in human biofluids that can be infected by C. acnes (serum, synovial fluid, cerebrospinal fluid). This study expands our understanding of how an environmental bacterium evolved to live on humans, and the assays developed in this work can now be used to identify this organism when it gains access to sterile sites to cause opportunistic infections.

Author Summary

The longer humans live, the more they require internal "replacement parts," like prosthetic joints. Increased placement of these and other medical devices has increased their complications, which frequently are infections caused by microbes that live on humans. One of these microbes is Cutibacterium acnes , which dominates 25% of human skin. It appears that when humans domesticated cattle, a C. acnes ancestor adapted from living in cows to living on people. One of these adaptations was RoxP, a protein only found in Cutibacterium and carried by all C. acnes . Here, we describe our extensive characterization of RoxP. We found that distantly related RoxP conserve high stability at the low pH found on human skin. They also conserve the ability to bind heme, a source of iron used by microbes when they infect humans. As a part of this work, we developed tests that measure RoxP to identify C. acnes growth. In a clinic or hospital, these tests could allow a doctor to rapidly identify C. acnes infections, which would improve patient outcomes and lower healthcare costs. This work has helped us better understand how C. acnes adapted to live on humans and to identify C. acnes infections of medical devices.

Vancomycin Soaking to Reduce Intraoperative Contamination by Cutibacterium acnes During the Latarjet Procedure

BACKGROUND

Postoperative infection after the Latarjet procedure, ranging from 1% to 6%, can compromise the functional outcome of young athletes. Cutibacterium acnes is a main pathogen as a consequence of an intraoperative contamination.

PURPOSE

To evaluate intraoperative contamination with C. acnes and the effectiveness of the local application of vancomycin during the Latarjet procedure.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

This was a single-center study including 75 patients (mean age, 26 years; range, 15-55 years) operated on for anterior shoulder instability with the primary open Latarjet procedure; they underwent the same protocol of skin preparation and preoperative prophylactic antibiotics. Three groups of 25 patients were created and divided sequentially, without the results of each group being known before the end of the study: group A (5 mg/mL of vancomycin), group B (20 mg/mL of vancomycin), and group C (control group with no vancomycin). Swab samples of the coracoid were taken before sectioning the coracoid process (time 1) and after its preparation (time 2). The coracoid was then wrapped in gauze impregnated with different concentrations of vancomycin, except for group C. A final sample (time 3) was taken before screwing the bone block onto the glenoid. All samples were cultured for 21 days, and patients underwent clinical and radiological follow-up for 6 months.

RESULTS

The C. acnes contamination rates at times 1, 2, and 3 were 25%, 44%, and 45%, respectively, without significant difference. There was no significant difference between groups A and B with respect to the number of positive cultures at each time point. Of 9 positive cultures at time 1, all were still positive at time 3 in group A, whereas 3 of 5 were negative in group B (P = .027). The rate of C. acnes at time 3 in the control group was higher than that in the 2 other groups (68% vs 44% for group A and 20% for group B; P = .003). Body mass index was the only prognostic factor for a C. acnes-positive culture (26.05 ± 3.39 vs 23.34 ± 2.33; P = .018). No clinical infection was reported at the 6-month postoperative follow-up.

CONCLUSION

The rate of C. acnes contamination ranged from 25% to 68% during the open Latarjet procedure in young athletes. Vancomycin reduced the bacterial contamination when it was used at high concentrations in a gauze wrap on the coracoid. The type of C. acnes detected and its clinical implications remain to be studied.

The skin microbiome stratifies patients with cutaneous T cell lymphoma and determines event-free survival

Mycosis fungoides (MF) is the most common entity of Cutaneous T cell lymphomas (CTCL) and is characterized by the presence of clonal malignant T cells in the skin. The role of the skin microbiome for MF development and progression are currently poorly understood. Using shotgun metagenomic profiling, real-time qPCR, and T cell receptor sequencing, we compared lesional and nonlesional skin of 20 MF patients with early and advanced MF. Additionally, we isolated Staphylococcus aureus and other bacteria from MF skin for functional profiling and to study the S. aureus virulence factor spa. We identified a subgroup of MF patients with substantial dysbiosis on MF lesions and concomitant outgrowth of S. aureus on plaque-staged lesions, while the other MF patients had a balanced microbiome on lesional skin. Dysbiosis and S. aureus outgrowth were accompanied by ectopic levels of cutaneous antimicrobial peptides (AMPs), including adaptation of the plaque-derived S. aureus strain. Furthermore, the plaque-derived S. aureus strain showed a reduced susceptibility towards antibiotics and an upregulation of the virulence factor spa, which may activate the NF-κB pathway. Remarkably, patients with dysbiosis on MF lesions had a restricted T cell receptor repertoire and significantly lower event-free survival. Our study highlights the potential for microbiome-modulating treatments targeting S. aureus to prevent MF progression.

Intratumoral Microbiome: Foe or Friend in Reshaping the Tumor Microenvironment Landscape?

The role of the microbiome in cancer and its crosstalk with the tumor microenvironment (TME) has been extensively studied and characterized. An emerging field in the cancer microbiome research is the concept of the intratumoral microbiome, which refers to the microbiome residing within the tumor. This microbiome primarily originates from the local microbiome of the tumor-bearing tissue or from translocating microbiome from distant sites, such as the gut. Despite the increasing number of studies on intratumoral microbiome, it remains unclear whether it is a driver or a bystander of oncogenesis and tumor progression. This review aims to elucidate the intricate role of the intratumoral microbiome in tumor development by exploring its effects on reshaping the multileveled ecosystem in which tumors thrive, the TME. To dissect the complexity and the multitude of layers within the TME, we distinguish six specialized tumor microenvironments, namely, the immune, metabolic, hypoxic, acidic, mechanical and innervated microenvironments. Accordingly, we attempt to decipher the effects of the intratumoral microbiome on each specialized microenvironment and ultimately decode its tumor-promoting or tumor-suppressive impact. Additionally, we portray the intratumoral microbiome as an orchestrator in the tumor milieu, fine-tuning the responses in distinct, specialized microenvironments and remodeling the TME in a multileveled and multifaceted manner.

Tackling transmission of infectious diseases: A probiotic-based system as a remedy for the spread of pathogenic and resistant microbes

Built environments (BEs) currently represent the areas in which human beings spend most of their life. Consistently, microbes populating BEs mostly derive from human occupants and can be easily transferred from BE to occupants. The hospital microbiome is a paradigmatic example, representing a reservoir for harmful pathogens that can be transmitted to susceptible patients, causing the healthcare-associated infections (HAIs). Environmental cleaning is a crucial pillar in controlling BE pathogens and preventing related infections, and chemical disinfectants have been largely used so far towards this aim. However, despite their immediate effect, chemical-based disinfection is unable to prevent recontamination, has a high environmental impact, and can select/increase antimicrobial resistance (AMR) in treated microbes. To overcome these limitations, probiotic-based sanitation (PBS) strategies were recently proposed, built on the use of detergents added with selected probiotics able to displace surrounding pathogens by competitive exclusion. PBS was reported as an effective and low-impact alternative to chemical disinfection, providing stable rebalance of the BE microbiome and significantly reducing pathogens and HAIs compared to disinfectants, without exacerbating AMR and pollution concerns. This minireview summarizes the most significant results obtained by applying PBS in sanitary and non-sanitary settings, which overall suggest that PBS may effectively tackle the infectious risk meanwhile preventing the further spread of pathogenic and resistant microbes.

Carbon source competition within the wound microenvironment can significantly influence infection progression

It is becoming increasingly apparent that commensal skin bacteria have an important role in wound healing and infection progression. However, the precise mechanisms underpinning many of these probiotic interactions remain to be fully uncovered. In this work, we demonstrate that the common skin commensal Cutibacterium acnes can limit the pathogenicity of the prevalent wound pathogen Pseudomonas aeruginosa in vivo. We show that this impact on pathogenicity is independent of any effect on growth, but occurs through a significant downregulation of the Type Three Secretion System (T3SS), the primary toxin secretion system utilised by P. aeruginosa in eukaryotic infection. We also show a downregulation in glucose acquisition systems, a known regulator of the T3SS, suggesting that glucose availability in a wound can influence infection progression. C. acnes is well known as a glucose fermenting organism, and we demonstrate that topically supplementing a wound with glucose reverses the probiotic effects of C. acnes. This suggests that introducing carbon source competition within the wound microenvironment may be an effective way to prevent or limit wound infection.

An Eastern County from an European Eastern Country-The Characteristics of Cutaneous Microbiome in Psoriasis Patients-Preliminary Results

The cutaneous microbiome represents a topic of high interest nowadays. Multiple studies have suggested the importance of the skin microbiome in different dermatological pathologies, highlighting the possible implications of cutaneous microorganisms in either the pathogenesis or prognosis of skin maladies. Psoriasis represents a common inflammatory skin disease, with a high prevalence in the worldwide population. The role of the cutaneous microbiome in psoriasis could explain a number of pathogenic theories and treatment objectives of this incurable skin disease. Our interest in the characteristics of the cutaneous microbiome, especially in psoriatic patients who attended a tertiary dermatological centre in Galati, Romania, is reflected in our current study, of which the preliminary results are discussed in this article. Using three types of skin sampling techniques (swabs, adhesive tape, and punch biopsies), we tried to characterise the microorganisms harboured in the skin of psoriatic patients and healthy individuals. This study was performed using culture-based probes, which were analysed using MALDI-TOF mass spectrometer equipment. Our preliminary results suggested that the greatest diversity was observed in the perilesional areas of psoriatic patients. The lowest cutaneous diversity was obtained from sampling psoriatic plaques. These results are similar to other studies of the cutaneous microbiome in psoriasis. The most frequent microorganisms found in all groups studied were of the Staphylococcus species: Staphylococcus epidermidis, Staphylococcus hominis, and Staphylococcus aureus. Analysing the living environment of each individual from this study, our preliminary results suggested different results from other studies, as higher diversity and heterogenicity was observed in urban environments than in rural living areas. Regarding the differences between sexes, our preliminary results showed higher quantitative and qualitative changes in the skin microbiome of male participants than female participants, opposite to the results found in other studies of the cutaneous microbiome in psoriasis. Given these preliminary results, we can conclude that we have found important differences by studying the cutaneous microbiome of psoriatic patients and healthy control individuals from a population that, to our knowledge, has not been yet studied from this point of view. Our results showed important characteristics of the skin microbiome in an Eastern European population, where cultural and environmental living habits could influence the cutaneous microbiome.

Dual intervention on the gut and skin microbiota attenuates facial cutaneous aging

The gut and skin microbiota are microbial barriers, resisting harmful foreign microorganisms and maintaining internal homeostasis. Dysbiosis of the gut and skin microbiota is involved in aging progression. However, interventions targeting facial skin wellness taking into account the gut-skin axis are scarce. In this study, the impact of an eight-week intervention with oral (O), topical (T), and both oral and topical (OT) xylo-oligosaccharides (XOS) by regulating gut and skin microbiota on facial cutaneous aging was investigated in a double-blind placebo-controlled trial in females. An increase in the proportion of participants with skin rejuvenation was observed, along with a significant reduction in facial pores after OT intervention. The reduction of cutaneous Cutibacterium by OT intervention was greater than that in the O and T groups. These interventions can change the skin microbial structure. Intestinal Bifidobacterium was enriched only by dual treatment with oral and topical XOS. Function prediction analysis revealed a decrease in K02770 encoding fructose-1-phosphate kinase involved in de novo lipid synthesis from fructose with dual intervention, suggesting that inhibition of lipophilic Cutibacterium may contribute to reducing facial pores. Overall, the dual XOS intervention approach is most effective for improving both gut and skin microbiota, as well as facial skin aging.

Exploring the possible relationship between skin microbiome and brain cognitive functions: a pilot EEG study

Human microbiota mainly resides on the skin and in the gut. Human gut microbiota can produce a variety of short chain fatty acids (SCFAs) that affect many physiological functions and most importantly modulate brain functions through the bidirectional gut-brain axis. Similarly, skin microorganisms also have identical metabolites of SCFAs reported to be involved in maintaining skin homeostasis. However, it remains unclear whether these SCFAs produced by skin bacteria can affect brain cognitive functions. In this study, we hypothesize that the brain's functional activities are associated with the skin bacterial population and examine the influence of local skin-bacterial growth on event-related potentials (ERPs) during an oddball task using EEG. Additionally, five machine learning (ML) methods were employed to discern the relationship between skin microbiota and cognitive functions. Twenty healthy subjects underwent three rounds of tests under different conditions-alcohol, glycerol, and water. Statistical tests confirmed a significant increase in bacterial population under water and glycerol conditions when compared to the alcohol condition. The metabolites of bacteria can turn phenol red from red-orange to yellow, confirming an increase in acidity. P3 amplitudes were significantly enhanced in response to only oddball stimulus at four channels (Fz, FCz, and Cz) and were observed after the removal of bacteria when compared with that under the water and glycerol manipulations. By using machine learning methods, we demonstrated that EEG features could be separated with a good accuracy (> 88%) after experimental manipulations. Our results suggest a relationship between skin microbiota and brain functions. We hope our findings motivate further study into the underlying mechanism. Ultimately, an understanding of the relationship between skin microbiota and brain functions can contribute to the treatment and intervention of diseases that link with this pathway.

Microbiome modulators for atopic eczema: a systematic review of experimental and investigational therapeutics

INTRODUCTION

Atopic dermatitis (AD) is a common inflammatory cutaneous disease that arises due to dysregulation of the Th2 immune response, impaired skin barrier integrity, and dysbiosis of the skin and gut microbiota. An abundance of Staphylococcus aureus biofilms in AD lesions increases the Th2 immune response, and gut bacteria release breakdown products such as Short Chain Fatty Acids that regulate the systemic immune response.

AREAS COVERED

We aim to evaluate therapies that modulate the microbiome in humans and discuss the clinical implications of these treatments. We performed a review of the literature in which 2,673 records were screened, and describe the findings of 108 studies that were included after full-text review. All included studies discussed the effects of therapies on the human microbiome and AD severity. Oral probiotics, topical probiotics, biologics, and investigational therapies were included in our analysis.

EXPERT OPINION

Oral probiotics demonstrate mixed efficacy at relieving AD symptoms. Topical probiotics reduce S. aureus abundance in AD lesional skin, yet for moderate-severe disease, these therapies may not reduce AD severity scores to the standard of biologics. Dupilumab and tralokinumab target key inflammatory pathways in AD and modulate the skin microbiome, further improving disease severity.

Rethinking Hidradenitis Suppurativa Management: Insights into Bacterial Interactions and Treatment Evolution

Hidradenitis suppurativa (HS), or acne inversa, is a chronic inflammatory dermatological condition characterized by painful and recurrent nodules and purulent abscesses. HS can have a devastating impact on the quality of life of patients. This condition is commonly localized to the axilla, groin, perineal, and inframammary regions, and can develop fistulas and sinus tracts over time. Its pathogenesis remains elusive and is best characterized at the moment as multi-factorial. Additionally, questions remain about the role of cutaneous dysbiosis as a primary HS trigger or as a secondary perturbation due to HS inflammation. This article features works in relation to HS and its interplay with bacterial microflora. We address current treatment approaches and their impact on HS-related bacteria, as well as areas of therapeutic innovation. In the future, disease-modifying or remittive therapy will likely combine an advanced/targeted anti-inflammatory approach with one that effectively modulates cutaneous and deep tissue dysbiosis.

The role of the skin microbiome in wound healing

The efficient management of skin wounds for rapid and scarless healing represents a major clinical unmet need. Nonhealing skin wounds and undesired scar formation impair quality of life and result in high healthcare expenditure worldwide. The skin-colonizing microbiota contributes to maintaining an intact skin barrier in homeostasis, but it also participates in the pathogenesis of many skin disorders, including aberrant wound healing, in many respects. This review focuses on the composition of the skin microbiome in cutaneous wounds of different types (i.e. acute and chronic) and with different outcomes (i.e. nonhealing and hypertrophic scarring), mainly based on next-generation sequencing analyses; furthermore, we discuss the mechanistic insights into host-microbe and microbe-microbe interactions during wound healing. Finally, we highlight potential therapeutic strategies that target the skin microbiome to improve healing outcomes.

Understanding Type 3 Innate Lymphoid Cells and Crosstalk with the Microbiota: A Skin Connection

Innate lymphoid cells (ILCs) are a diverse population of lymphocytes classified into natural killer (NK) cells, ILC1s, ILC2s, ILC3s, and ILCregs, broadly following the cytokine secretion and transcription factor profiles of classical T cell subsets. Nonetheless, the ILC lineage does not have rearranged antigen-specific receptors and possesses distinct characteristics. ILCs are found in barrier tissues such as the skin, lungs, and intestines, where they play a role between acquired immune cells and myeloid cells. Within the skin, ILCs are activated by the microbiota and, in turn, may influence the microbiome composition and modulate immune function through cytokine secretion or direct cellular interactions. In particular, ILC3s provide epithelial protection against extracellular bacteria. However, the mechanism by which these cells modulate skin health and homeostasis in response to microbiome changes is unclear. To better understand how ILC3s function against microbiota perturbations in the skin, we propose a role for these cells in response to Cutibacterium acnes, a predominant commensal bacterium linked to the inflammatory skin condition, acne vulgaris. In this article, we review current evidence describing the role of ILC3s in the skin and suggest functional roles by drawing parallels with ILC3s from other organs. We emphasize the limited understanding and knowledge gaps of ILC3s in the skin and discuss the potential impact of ILC3-microbiota crosstalk in select skin diseases. Exploring the dialogue between the microbiota and ILC3s may lead to novel strategies to ameliorate skin immunity.

Bacteria-based drug delivery for treating non-oncological diseases

Bacteria inhabit all over the human body, especially the skin, gastrointestinal tract, respiratory tract, urogenital tract, as well as specific lesion sites, such as wound and tumor. By leveraging their distinctive attributes including rapid proliferation, inherent abilities to colonize various biointerfaces in vivo and produce diverse biomolecules, and the flexibility to be functionalized via genetic engineering or surface modification, bacteria have been widely developed as living therapeutic agents, showing promising potential to make a great impact on the exploration of advanced drug delivery systems. In this review, we present an overview of bacteria-based drug delivery and its applications in treating non-oncological diseases. We systematically summarize the physiological positions where living bacterial therapeutic agents can be delivered to, including the skin, gastrointestinal tract, respiratory tract, and female genital tract. We discuss the success of using bacteria-based drug delivery systems in the treatment of diseases that occur in specific locations, such as skin wound healing/infection, inflammatory bowel disease, respiratory diseases, and vaginitis. We also discuss the advantages as well as the limitations of these living therapeutics and bacteria-based drug delivery, highlighting the key points that need to be considered for further translation. This review article may provide unique insights for designing next-generation bacteria-based therapeutics and developing advanced drug delivery systems.

Infectious disease for the rhinologist

PURPOSE OF REVIEW

The purpose of this review is to summarize the recent literature relating to viral, fungal and bacterial infections and their interactions within the sinonasal tract in the past 18 months.

RECENT FINDINGS

Coronavirus disease 2019 (COVID-19)-associated olfactory dysfunction (OD) is variant dependent. Magnetic resonance imaging studies have found greater olfactory cleft opacification and higher olfactory bulb volume in post-COVID-19 OD. Olfactory training remains the mainstay of treatment, while platelet-rich plasma injections and ultramicronized palmitoylethanolamide and luteolin combination oral supplementation have shown early promise.Consensus statements on paranasal sinus fungal balls and acute invasive fungal sinusitis have been released.Studies on the nasal microbiome have reported Staphylococcus and Corynebacterium as the most abundant genera, with higher levels of Staphylococcus and Corynebacterium being found in patients with chronic rhinosinusitis (CRS) and healthy individuals respectively. However, there is conflicting evidence on the significance of biodiversity of the nasal microbiome found in CRS versus healthy patients.

SUMMARY

While the peak of the COVID-19 pandemic is behind us, its sequelae continue to pose treatment challenges. Further studies in OD have implications in managing the condition, beyond those afflicted post-COVID-19 infection. Similarly, more research is needed in studying the nasal microbiome and its implications in the development and treatment of CRS.

Microbe Interactions within the Skin Microbiome

The skin is the largest human organ and is responsible for many important functions, such as temperature regulation, water transport, and protection from external insults. It is colonized by several microorganisms that interact with each other and with the host, shaping the microbial structure and community dynamics. Through these interactions, the skin microbiota can inhibit pathogens through several mechanisms such as the production of bacteriocins, proteases, phenol soluble modulins (PSMs), and fermentation. Furthermore, these commensals can produce molecules with antivirulence activity, reducing the potential of these pathogens to adhere to and invade human tissues. Microorganisms of the skin microbiota are also able to sense molecules from the environment and shape their behavior in response to these signals through the modulation of gene expression. Additionally, microbiota-derived compounds can affect pathogen gene expression, including the expression of virulence determinants. Although most studies related to microbial interactions in the skin have been directed towards elucidating competition mechanisms, microorganisms can also use the products of other species to their benefit. In this review, we will discuss several mechanisms through which microorganisms interact in the skin and the biotechnological applications of products originating from the skin microbiota that have already been reported in the literature.

Quantitative Aggregation of Microbiome Sequencing Data Provides Insights into the Associations between the Skin Microbiome and Psoriasis

Although prior studies have reported distinct skin microbiome profiles associated with psoriasis, differences in methods and analyses limit generalizable conclusions. Individual studies have actually reported conflicting findings; for example, Propionibacterium and Staphylococcus have been significantly associated with both psoriatic lesions and healthy skin. Qualitative reviews have attempted to summarize this body of work, but there is great variability across the studies' findings and methods. To better unify these data, we created a meta-analysis of all publicly available datasets by utilizing a uniform bioinformatics pipeline and reference database to investigate associations of the skin microbiome in psoriasis. A total of 977 skin swab samples (341 lesional, 295 nonlesional, and 341 healthy) from 6 studies were analyzed. The aggregated analysis revealed a higher relative abundance of microorganisms, including Staphylococcus aureus and Corynebacterium simulans, among others, from patients with psoriasis than those from healthy swab samples; in addition, Cutibacterium acnes, Lawsonella unclassified, and S warneri were significantly higher in healthy samples. Furthermore, comparison of functional pathways predicted from 16S gene markers showed that L-ornithine biosynthesis and L-histidine biosynthesis were lower in psoriatic lesions than in healthy controls. Taken together, this meta-analysis allows for a more generalizable association between the skin microbiome and psoriasis.

Effect of lactic acid bacteria fermentation on cow milk allergenicity and antigenicity: A review

Cow milk is a major allergenic food. The potential prevention and treatment effects of lactic acid bacteria (LAB)-fermented dairy products on allergic symptoms have garnered considerable attention. Cow milk allergy (CMA) is mainly attributed to extracellular and/or cell envelope proteolytic enzymes with hydrolysis specificity. Numerous studies have demonstrated that LAB prevents the risk of allergies by modulating the development and regulation of the host immune system. Specifically, LAB and its effectors can enhance intestinal barrier function and affect immune cells by interfering with humoral and cellular immunity. Fermentation hydrolysis of allergenic epitopes is considered the main mechanism of reducing CMA. This article reviews the linear epitopes of allergens in cow milk and the effect of LAB on these allergens and provides insight into the means of predicting allergenic epitopes by conventional laboratory analysis methods combined with molecular simulation. Although LAB can reduce CMA in several ways, the mechanism of action remains partially clarified. Therefore, this review additionally attempts to summarize the main mechanism of LAB fermentation to provide guidance for establishing an effective preventive and treatment method for CMA and serve as a reference for the screening, research, and application of LAB-based intervention.

Scalp bacterial species influence SIRT1 and TERT expression in keratinocytes

Scalp bacteria on the human scalp and scalp hair comprise distinct community structures for sites and individuals. To evaluate their effect on human keratinocyte cellular activity, including that of the hair follicular keratinocytes, the expression of several longevity genes was examined using HaCaT cells. A screening system that uses enhanced green fluorescent protein (EGFP) fluorescence was established to identify scalp bacteria that enhance silent mating type information regulation 2 homolog-1 (SIRT1) promoter activity in transformed HaCaT cells (SIRT1p-EGFP). The results of quantitative polymerase chain reaction revealed that several predominant scalp bacteria enhanced (Cutibacterium acnes and Pseudomonas lini) and repressed (Staphylococcus epidermidis) the expressions of SIRT1 and telomerase reverse transcriptase (TERT) genes in HaCaT cells. These results suggest that the predominant scalp bacteria are related to the health of the scalp and hair, including repair of the damaged scalp and hair growth, by regulating gene expression in keratinocytes.

Screening and evaluation of skin potential probiotic from high-altitude Tibetans to repair ultraviolet radiation damage

Human skin microbes play critical roles in skin health and diseases. Microbes colonizing on the skin of Tibetans living in the high-altitude area for generations may have a stronger ability to resist the harsh environment, such as high ultraviolet radiation (UV). Isolation of a potential probiotic from Tibetans skin is beneficial for resistance of skin disease for humans in the world. In this study, the signature microbiota for Tibetan skin were characterized compared to low-altitude humans. Next, using culture-omics, 118 species were isolated. The culturability of high-altitude of Tibetan skin microbiome reached approximate 66.8%. Next, we found that one strain, Pantoea eucrina, had the greatest ability to repair UV damage to the skin as the lowest pathological score was observed in this group. Interestingly, another animal trial found this bacterium resisted UV rather than its metabolites. Using whole genome sequencing, this strain P. eucrina KBFS172 was confirmed, and its functions were annotated. It might involve in the metabolic pathway of carotenoid biosynthesis with anti-oxidative stress properties, which plays critical roles in UV-damage repair. In conclusion, we characterized the signature microbes of skin in high-altitude Tibetans, isolated a skin bacterium of Pantoea eucrina KBFS172 which could repair UV damage via involving the metabolic pathway of carotenoid biosynthesis. Our results provide a new potential skin probiotic for skin disease prevention or sunburn.

New insights into the role of Cutibacterium acnes-derived extracellular vesicles in inflammatory skin disorders

Cutibacterium acnes (C. acnes) is one of the most prevalent bacteria that forms the human skin microbiota. Specific phylotypes of C. acnes have been associated with the development of acne vulgaris, while other phylotypes have been linked to healthy skin. In this scenario, bacterial extracellular vesicles (EVs) play a role in the interkingdom communication role with the human host. The purpose of this study was to examine the impact of EVs generated by various phylotypes of C. acnes on inflammation and sebum production using different in vitro skin cell types. The main findings of this study reveal that the proteomic profile of the cargo embodied in the EVs reflects distinct characteristics of the different C. acnes phylotypes in terms of life cycle, survival, and virulence. The in vitro skin cell types showed an extended pro-inflammatory modulation of SLST A1 EVs consistently triggering the activation of the inflammation-related factors IL-8, IL-6, TNFα and GM-CSF, in comparison to SLST H1 and SLST H2. Additionally, an acne-prone skin model utilizing PCi-SEB and arachidonic acid as a sebum inducer, was employed to investigate the impact of C. acnes EVs on sebum regulation. Our findings indicated that all three types of EVs significantly inhibited sebum production after a 24-h treatment period, with SLST H1 EVs exhibiting the most pronounced inhibitory effect when compared to the positive control. The results of this study highlight the protective nature of C. acnes SLST H1 EVs and their potential use as a natural treatment option for alleviating symptoms associated with inflammation and oily skin.

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

AIMS

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

METHODS AND RESULTS

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

CONCLUSIONS

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

Commensal Cutibacterium acnes induce epidermal lipid synthesis important for skin barrier function

Lipid synthesis is necessary for formation of epithelial barriers and homeostasis with external microbes. An analysis of the response of human keratinocytes to several different commensal bacteria on the skin revealed that Cutibacterium acnes induced a large increase in essential lipids including triglycerides, ceramides, cholesterol, and free fatty acids. A similar response occurred in mouse epidermis and in human skin affected with acne. Further analysis showed that this increase in lipids was mediated by short-chain fatty acids produced by Cutibacterium acnes and was dependent on increased expression of several lipid synthesis genes including glycerol-3-phosphate-acyltransferase-3. Inhibition or RNA silencing of peroxisome proliferator-activated receptor-α (PPARα), but not PPARβ and PPARγ, blocked this response. The increase in keratinocyte lipid content improved innate barrier functions including antimicrobial activity, paracellular diffusion, and transepidermal water loss. These results reveal that metabolites from a common commensal bacterium have a previously unappreciated influence on the composition of epidermal lipids.

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

Background

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

Methods

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

Results

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

Conclusion

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

Fish collagen peptides' modulating effect on human skin microbiota against pathogenic Staphylococcus aureus

Aim: The current research aims to design effective strategies to enhance the body's immune system against pathogenic bacteria. Methods: Skin commensals were isolated, identified and cultured in fish collagen peptides (FCPs). Results: After culturing in FCP, the skin commensals were used in a dose-dependent manner for Staphylococcus aureus in a dual-culture test, which showed significant growth inhibition of the pathogenic bacteria, which concluded that FCP induced the immune defense system of skin microbiota against pathogenic strains. Conclusion: Results have validated that fish collagen peptide plays a vital role in the growth of selected human skin flora and induces more defensive immunity against pathogenic S. aureus bacteria in dual-culture experimentation.

Darier's disease exhibits a unique cutaneous microbial dysbiosis associated with inflammation and body malodour

BACKGROUND

Darier's disease (DD) is a genodermatosis caused by mutations of the ATP2A2 gene leading to disrupted keratinocyte adhesion. Recurrent episodes of skin inflammation and infections with a typical malodour in DD indicate a role for microbial dysbiosis. Here, for the first time, we investigated the DD skin microbiome using a metabarcoding approach of 115 skin swabs from 14 patients and 14 healthy volunteers. Furthermore, we analyzed its changes in the context of DD malodour and the cutaneous DD transcriptome.

RESULTS

We identified a disease-specific cutaneous microbiome with a loss of microbial diversity and of potentially beneficial commensals. Expansion of inflammation-associated microbes such as Staphylococcus aureus and Staphylococcus warneri strongly correlated with disease severity. DD dysbiosis was further characterized by abundant species belonging to Corynebacteria, Staphylococci and Streptococci groups displaying strong associations with malodour intensity. Transcriptome analyses showed marked upregulation of epidermal repair, inflammatory and immune defence pathways reflecting epithelial and immune response mechanisms to DD dysbiotic microbiome. In contrast, barrier genes including claudin-4 and cadherin-4 were downregulated.

CONCLUSIONS

These findings allow a better understanding of Darier exacerbations, highlighting the role of cutaneous dysbiosis in DD inflammation and associated malodour. Our data also suggest potential biomarkers and targets of intervention for DD. Video Abstract.

Microbiota and IL-33/31 Axis Linkage: Implications and Therapeutic Perspectives in Atopic Dermatitis and Psoriasis

Microbiome dysbiosis and cytokine alternations are key features of atopic dermatitis (AD) and psoriasis (PsO), two of the most prevalent and burdensome pruritic skin conditions worldwide. Interleukin (IL)-33 and IL-31 have been recognized to be major players who act synergistically in the pathogenesis and maintenance of different chronic inflammatory conditions and pruritic skin disorders, including AD and PsO, and their potential role as therapeutic targets is being thoroughly investigated. The bidirectional interplay between dysbiosis and immunological changes has been extensively studied, but there is still debate regarding which of these two factors is the actual causative culprit behind the aetiopathological process that ultimately leads to AD and PsO. We conducted a literature review on the Pubmed database assessing articles of immunology, dermatology, microbiology and allergology with the aim to strengthen the hypothesis that dysbiosis is at the origin of the IL-33/IL-31 dysregulation that contributes to the pathogenesis of AD and PsO. Finally, we discussed the therapeutic options currently in development for the treatment of these skin conditions targeting IL-31, IL-33 and/or the microbiome.

The dynamic balance of the skin microbiome across the lifespan

For decades research has centered on identifying the ideal balanced skin microbiome that prevents disease and on developing therapeutics to foster this balance. However, this single idealized balance may not exist. The skin microbiome changes across the lifespan. This is reflected in the dynamic shifts of the skin microbiome's diverse, inter-connected community of microorganisms with age. While there are core skin microbial taxa, the precise community composition for any individual person is determined by local skin physiology, genetics, microbe-host interactions, and microbe-microbe interactions. As a key interface with the environment, the skin surface and its appendages are also constantly exchanging microbes with close personal contacts and the environment. Hormone fluctuations and immune system maturation also drive age-dependent changes in skin physiology that support different microbial community structures over time. Here, we review recent insights into the factors that shape the skin microbiome throughout life. Collectively, the works summarized within this review highlight how, depending on where we are in lifespan, our skin supports robust microbial communities, while still maintaining microbial features unique to us. This review will also highlight how disruptions to this dynamic microbial balance can influence risk for dermatological diseases as well as impact lifelong health.

The Skin Microbiome: Current Landscape and Future Opportunities

Our skin is the largest organ of the body, serving as an important barrier against the harsh extrinsic environment. Alongside preventing desiccation, chemical damage and hypothermia, this barrier protects the body from invading pathogens through a sophisticated innate immune response and co-adapted consortium of commensal microorganisms, collectively termed the microbiota. These microorganisms inhabit distinct biogeographical regions dictated by skin physiology. Thus, it follows that perturbations to normal skin homeostasis, as occurs with ageing, diabetes and skin disease, can cause microbial dysbiosis and increase infection risk. In this review, we discuss emerging concepts in skin microbiome research, highlighting pertinent links between skin ageing, the microbiome and cutaneous repair. Moreover, we address gaps in current knowledge and highlight key areas requiring further exploration. Future advances in this field could revolutionise the way we treat microbial dysbiosis associated with skin ageing and other pathologies.

The Antimicrobial Effect of Various Single-Strain and Multi-Strain Probiotics, Dietary Supplements or Other Beneficial Microbes against Common Clinical Wound Pathogens

The skin is the largest organ in the human body and is colonized by a diverse microbiota that works in harmony to protect the skin. However, when skin damage occurs, the skin microbiota is also disrupted, and pathogens can invade the wound and cause infection. Probiotics or other beneficial microbes and their metabolites are one possible alternative treatment for combating skin pathogens via their antimicrobial effectiveness. The objective of our study was to evaluate the antimicrobial effect of seven multi-strain dietary supplements and eleven single-strain microbes that contain probiotics against 15 clinical wound pathogens using the agar spot assay, co-culturing assay, and agar well diffusion assay. We also conducted genera-specific and species-specific molecular methods to detect the DNA in the dietary supplements and single-strain beneficial microbes. We found that the multi-strain dietary supplements exhibited a statistically significant higher antagonistic effect against the challenge wound pathogens than the single-strain microbes and that lactobacilli-containing dietary supplements and single-strain microbes were significantly more efficient than the selected propionibacteria and bacilli. Differences in results between methods were also observed, possibly due to different mechanisms of action. Individual pathogens were susceptible to different dietary supplements or single-strain microbes. Perhaps an individual approach such as a 'probiogram' could be a possibility in the future as a method to find the most efficient targeted probiotic strains, cell-free supernatants, or neutralized cell-free supernatants that have the highest antagonistic effect against individual clinical wound pathogens.

Fermented Cosmetics and Metabolites of Skin Microbiota—A New Approach to Skin Health

The skin covers our entire body and is said to be the “largest organ of the human body”. It has many health-maintaining functions, such as protecting the body from ultraviolet rays and dryness and maintaining body temperature through energy metabolism. However, the number of patients suffering from skin diseases, including atopic dermatitis, is increasing due to strong irritation of the skin caused by detergents that are spread by the development of the chemical industry. The skin is inhabited by about 102–107 cells/cm2 and 1000 species of commensal bacteria, fungi, viruses, and other microorganisms. In particular, metabolites such as fatty acids and glycerol released by indigenous skin bacteria have been reported to have functional properties for the health of the skin. Therefore, skin-domesticating bacteria and the metabolites derived from those bacteria are used in many skincare product ingredients and function as probiotic cosmetics. Japanese traditional fermented stuff, used as foods in Japan for over 1300 years, are now being applied as fermented cosmetics. Fermented cosmetics are expected to have multifaceted health functionality and continue to grow as products in the natural skincare product market. In this review, we consider approaches to skin health using fermented cosmetics and modulation of skin microflora metabolites.

Lactobacillus delbrueckii subsp. bulgaricus strain TCI904 reduces body weight gain, modulates immune response, improves metabolism and anxiety in high fat diet-induced obese mice

The multiple probiotic characteristics of strain TCI904 isolated in this study from natural fermented milk were investigated using a mouse model. TCI904 was identified as Lactobacillus delbrueckii subsp. bulgaricu (LDB), a well-known lactic acid starter bacterium found in yogurt. TCI904 exhibited an outstanding pancreatic lipase inhibition activity among several strains of lactic acid bacteria in vitro. Its in vivo effects were further studied. In a comparison of mice fed a high-fat diet (HFD) and those fed a HFD combined with TCI904 for 9 weeks, differences were observed in various aspects of health, and the adverse effects of a HFD were prevented in the latter group. TCI904 effectively prevented fat and body weight accumulation without reducing food intake; it also modulated innate immunity and increased the level of IgA in feces, reversing the increased blood sugar and insulin levels and attenuated the hyperlipidemia caused by a HFD. Based on biochemical test data, compared with the HFD group, a HFD combined with TCI904 induced significant lowering of insulin resistance indicator, homeostasis model assessment-insulin resistance (HOMA-IR) and atherogenic indices of plasma (AIP), the atherogenic coefficient (AC) and cardiac risk ratio (CRR) and increased the cardioprotective index (CPI). In addition, the administration of TCI904 alleviated mood disorders caused by a HFD. Taking the recommended human dose of TCI904 did not affect the liver or kidney function, indicating that TCI904 has sufficient in vivo safety. Taken together, the results of the present study contributed towards validation of the probiotic benefits of lactic acid starter microflora. Orally taken TCI904 exhibited positive immune- and metabolic-modulating, and anxiolytic properties, especially in HFD-induced obesity.

Surgical site infection following orthopedic surgery in a patient with acne: A challenging case

Propionibacterium acnes is a typical component of the human body's flora and has been implicated as the causative infectious agent following a variety of operations, including device installation. We present a case of a 21-year-old male patient with severe global acneiform eruption with a non-healing limb lesion near the orthopedic surgery incisions.

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

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

Effect of a Novel E3 Probiotics Formula on the Gut Microbiome in Atopic Dermatitis Patients: A Pilot Study

Atopic dermatitis (AD) has been shown to be closely related to gut dysbiosis mediated through the gut−skin axis, and thus the gut microbiome has recently been explored as a potential therapeutic target for the treatment of AD. Contrasting and varying efficacy have been reported since then. In order to investigate the determining factor of probiotics responsiveness in individuals with AD, we initiated the analysis of 41 AD patients with varying disease severity in Hong Kong, whereas the severity was assessed by Eczema Area and Severity Index (EASI) by board certified dermatologist. 16S rRNA sequencing on the fecal samples from AD patients were performed to obtain the metagenomics profile at baseline and after 8 weeks of oral administration of a novel E3 probiotics formula (including prebiotics, probiotics and postbiotics). While EASI of the participants were significantly lower after the probiotics treatment (p < 0.001, paired Wilcoxon signed rank), subjects with mild AD were found to be more likely to respond to the probiotics treatment. Species richness among responders regardless of disease severity were significantly increased (p < 0.001, paired Wilcoxon signed rank). Responders exhibited (1) elevated relative abundance of Clostridium, Fecalibacterium, Lactobacillus, Romboutsia, and Streptococcus, (2) reduced relative abundance of Collinsella, Bifidobacterium, Fusicatenibacter, and Escherichia-Shigella amid orally-intake probiotics identified using the machine learning algorithm and (3) gut microbiome composition and structure resembling healthy subjects after probiotics treatment. Here, we presented the gut microbiome dynamics in AD patients after the administration of the E3 probiotics formula and delineated the unique gut microbiome signatures in individuals with AD who were responding to the probiotics. These findings could guide the future development of probiotics use for AD management.

Extracellular electrons transferred from honey probiotic Bacillus circulans inhibits inflammatory acne vulgaris

Bacillus circulans (B. circulans) is widely used as an electrogenic bacterium in microbial fuel cell (MFC) technology. This study evaluated whether B. circulans can ferment glucose to generate electricity and mitigate the effects of human skin pathogens. The electricity production of B. circulans was examined by measuring the voltage difference and verified using a ferrozine assay in vitro. To investigate the fermentation effects of B. circulans on inhibition of human skin pathogens, Cutibacterium acnes (C. acnes) was injected intradermally into mice ears to induce an inflammatory response. The results revealed that the glucose-B. circulans co-culture enhanced electricity production and significantly supressed C. acnes growth. The addition of roseoflavin to inhibit flavin production considerably reduced the electrical energy generated by B. circulans through metabolism and, in vivo test, recovered C. acnes count and macrophage inflammatory protein 2 (MIP-2) levels. This suggests that B. circulans can generate electrons that affect the growth of C. acnes through flavin-mediated electron transfer and alleviate the resultant inflammatory response. Our findings demonstrate that probiotics separated from natural substances and antimicrobial methods of generating electrical energy through carbon source fermentation can help in the treatment of bacterial infections.

Probing Beyond the Pain Scale: A Rare Case of Cutibacterium Acnes Septic Arthritis

Patients with sickle cell disease frequently present to the hospital for pain control secondary to vaso-occlusive crises (VOCs). Diagnostic challenges exist for healthcare providers in distinguishing joint pain secondary to a VOC from an intraarticular infection at initial presentation due to the lack of established clinical markers exclusive to one or the other. We present a 35-year-old female with sickle cell disease and avascular necrosis of bilateral hips and the right shoulder with several previous admissions for VOC pain control complaining of a "different" kind of pain in her shoulder. Treated initially for pain control, our patient was found to be suffering from culture-positive septic arthritis of the shoulder with Cutibacterium acnes, a rare source of de novo intraarticular infection. This case highlights the importance of incorporating patients' subjective descriptions of illness into differential diagnosis considerations, notably for those caring for patients with sickle cell disease. This case also establishes C. acnes as a rare organism responsible for de novo septic arthritis in the setting of sickle cell disease.

Chitogel following endoscopic sinus surgery promotes a healthy microbiome and reduces postoperative infections

BACKGROUND

Postoperative infections following endoscopic sinus surgery (ESS) impair wound healing and lead to poor outcomes. The aim of this study is to assess the effectiveness of Chitogel to reduce postoperative infections and restore a healthy microbiome following ESS.

METHODS

In this double-blinded randomized control trial, 25 patients undergoing ESS were prospectively recruited. At the end of surgery, patients were randomized to receive Chitogel to one side of the sinuses (allowing the other side to serve as control). Patients underwent routine follow-up with nasoendoscopies performed at 2, 6, and 12 weeks postoperatively. Sinus ostial measurements, microbiology, and microbiome swabs from bilateral sides were collected intraoperatively and at 12 weeks postoperatively. Additional swabs were collected if infection was present.

RESULTS

Improved endoscopic appearance of the sinuses (p = 0.03) and ostial patency were noted on the Chitogel side compared with control at 12 weeks (p < 0.001). A significant decrease in infections on the Chitogel side (12.0%) compared with control (52.0%) (p = 0.005) was evident. Following the use of Chitogel, there was a significant increase in the combined relative abundance of commensals Corynebacterium and Cutibacterium (Propionibacterium) from 30.15% at baseline to 46.62% at 12 weeks compared with control (47.18% to 40.79%) (p.adj = 0.01).

CONCLUSION

Chitogel significantly improved both the nasoendoscopic appearance of the sinuses and sinus ostial patency at 12 weeks postoperatively. Chitogel used following ESS helps restore an improved microbiome resulting in an increase in the relative abundance of commensals Corynebacterium and Cutibacterium (Propionibacterium). A significant decrease in postoperative infections was noted following use of Chitogel.

Skin Microbiome Variation with Cancer Progression in Human Cutaneous Squamous Cell Carcinoma

The skin microbiome plays a critical role in skin homeostasis and disorders. UVR is the major cause of nonmelanoma skin cancer, but other risk factors, including immune suppression, chronic inflammation, and antibiotic usage, suggest the microbiome as an additional, unexplored risk factor and potential disease biomarker. The overarching goal was to study the skin microbiome in squamous cell carcinoma (SCC) and premalignant actinic keratosis compared with that in healthy skin to identify skin cancer‒associated changes in the skin microbiome. We performed a high-resolution analysis of shotgun metagenomes of actinic keratosis and SCC in healthy skin, revealing the microbial community shifts specific to actinic keratosis and SCC. Most prominently, the relative abundance of pathobiont Staphylococcus aureus was increased at the expense of commensal Cutibacterium acnes in SCC compared with that in healthy skin, and enrichment of functional pathways in SCC reflected this shift. Notably, C. acnes associated with lesional versus healthy skin differed at the strain level, suggesting the specific functional changes associated with its depletion in SCC. Our study revealed a transitional microbial dysbiosis from healthy skin to actinic keratosis to SCC, supporting further investigation of the skin microbiome for use as a biomarker and providing hypotheses for studies investigating how these microbes might influence skin cancer progression.

Ecological Processes and Human Behavior Provide a Framework for Studying the Skin Microbial Metacommunity

Metacommunity theory dictates that a microbial community is supported both by local ecological processes and the dispersal of microbes between neighboring communities. Studies that apply this perspective to human-associated microbial communities are thus far limited to the gut microbiome. Yet, the skin serves as the primary barrier between the body and the external environment, suggesting frequent opportunities for microbial dispersal to the variable microbial communities that are housed across skin sites. This paper applies metacommunity theory to understand the dispersal of microbes to the skin from the physical and social environment, as well as between different skin sites on an individual's body. This includes highlighting the role of human behavior in driving microbial dispersal, as well as shaping physiological properties of skin that underscore local microbial community dynamics. By leveraging data from research on the skin microbiomes of amphibians and other animals, this paper provides recommendations for future research on the skin microbial metacommunity, including generating testable predictions about the ecological underpinnings of the skin microbiome.

Factors influencing development of the infant microbiota: from prenatal period to early infancy

During early life, the gut microbial composition rapidly changes by maternal microbiota composition, delivery mode, infant feeding mode, antibiotic usage, and various environmental factors, such as the presence of pets and siblings. An integrative study on the diet, the microbiota, and genomic activity at the transcriptomic level may give an insight into the role of diet in shaping the human/microbiome relationship. Disruption in the gut microbiota (i.e., gut dysbiosis) has been linked to necrotizing enterocolitis in infancy, as well as some chronic diseases in later, including obesity, diabetes, inflammatory bowel disease, cancer, allergies, and asthma. Therefore, understanding the impact of maternal-to-infant transfer of dysbiotic microbes and then modifying infant early colonization or correcting early-life gut dysbiosis might be a potential strategy to overcome chronic health conditions.

A dysregulated sebum-microbial metabolite-IL-33 axis initiates skin inflammation in atopic dermatitis

Microbial dysbiosis in the skin has been implicated in the pathogenesis of atopic dermatitis (AD); however, whether and how changes in the skin microbiome initiate skin inflammation, or vice versa, remains poorly understood. Here, we report that the levels of sebum and its microbial metabolite, propionate, were lower on the skin surface of AD patients compared with those of healthy individuals. Topical propionate application attenuated skin inflammation in mice with MC903-induced AD-like dermatitis by inhibiting IL-33 production in keratinocytes, an effect that was mediated through inhibition of HDAC and regulation of the AhR signaling pathway. Mice lacking sebum spontaneously developed AD-like dermatitis, which was improved by topical propionate application. A proof-of-concept clinical study further demonstrated the beneficial therapeutic effects of topical propionate application in AD patients. In summary, we have uncovered that the dysregulated sebum-microbial metabolite-IL-33 axis might play an initiating role in AD-related skin inflammation, thereby highlighting novel therapeutic strategies for the treatment of AD.

Gut microbiota in various childhood disorders: Implication and indications

Gut microbiota has a significant role in gut development, maturation, and immune system differentiation. It exerts considerable effects on the child's physical and mental development. The gut microbiota composition and structure depend on many host and microbial factors. The host factors include age, genetic pool, general health, dietary factors, medication use, the intestine's pH, peristalsis, and transit time, mucus secretions, mucous immunoglobulin, and tissue oxidation-reduction potentials. The microbial factors include nutrient availability, bacterial cooperation or antagonism, and bacterial adhesion. Each part of the gut has its microbiota due to its specific characteristics. The gut microbiota interacts with different body parts, affecting the pathogenesis of many local and systemic diseases. Dysbiosis is a common finding in many childhood disorders such as autism, failure to thrive, nutritional disorders, coeliac disease, Necrotizing Enterocolitis, helicobacter pylori infection, functional gastrointestinal disorders of childhood, inflammatory bowel diseases, and many other gastrointestinal disorders. Dysbiosis is also observed in allergic conditions like atopic dermatitis, allergic rhinitis, and asthma. Dysbiosis can also impact the development and the progression of immune disorders and cardiac disorders, including heart failure. Probiotic supplements could provide some help in managing these disorders. However, we are still in need of more studies. In this narrative review, we will shed some light on the role of microbiota in the development and management of common childhood disorders.

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

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

Characterization of the skin microbiota in bullous pemphigoid patients and controls reveals novel microbial indicators of disease

INTRODUCTION

Bullous pemphigoid (BP) is the most common autoimmune blistering disease. It predominately afflicts the elderly and is significantly associated with increased mortality. The observation of age-dependent changes in the skin microbiota as well as its involvement in other inflammatory skin disorders suggests that skin microbiota may play a role in the emergence of BP blistering. We hypothesize that changes in microbial diversity associated with BP might occur before the emergence of disease lesions, and thus could represent an early indicator of blistering risk.

OBJECTIVES

The present study aims to investigate potential relationships between skin microbiota and BP and elaborate on important changes in microbial diversity associated with blistering in BP.

METHODS

The study consisted of an extensive sampling effort of the skin microbiota in patients with BP and age- and sex-matched controls to analyze whether intra-individual, body site, and/or geographical variation correlate with changes in skin microbial composition in BP and/or blistering status.

RESULTS

We find significant differences in the skin microbiota of patients with BP compared to that of controls, and moreover that disease status rather than skin biogeography (body site) governs skin microbiota composition in patients with BP. Our data reveal a discernible transition between normal skin and the skin surrounding BP lesions, which is characterized by a loss of protective microbiota and an increase in sequences matching Staphylococcus aureus, a known inflammation-promoting species. Notably, Staphylococcus aureus is ubiquitously associated with BP disease status, regardless of the presence of blisters.

CONCLUSION

The present study suggests Staphylococcus aureus may be a key taxon associated with BP disease status. Importantly, we however find contrasting patterns in the relative abundances of Staphylococcus hominis and Staphylococcus aureus reliably discriminate between patients with BP and matched controls. This may serve as valuable information for assessing blistering risk and treatment outcomes in a clinical setting.

Is clindamycin a potential treatment for prostatitis?

Cutibacterium acnes has been associated with chronic prostatitis, which can potentially favor the appearance of tumors in the prostate. Prostatitis is difficult to treat, and the drug needs to be able to penetrate the prostate. The aim was to investigate the pharmacokinetics of clindamycin in the interstitial fluid of rat prostate using microdialysis. Microdialysis probes were recovered in vitro and in vivo. Clindamycin was administered at 80 mg/kg iv bolus for plasma and tissue pharmacokinetic experiments. A microdialysis probe was implanted in the prostate gland for collections over an 8-hour period. The pharmacokinetic parameters were determined by both compartmental and non-compartmental approaches. Penetration was determined as the ratio between the area under the curve and the time of the clindamycin measurement in the prostate. The recovery of the in vivo probes was 38.11 ± 1.14%. The plasma profile was modeled by a two-compartment pharmacokinetic model. Clindamycin presented a prostate/plasma ratio of 1.02, with free concentrations above the minimum inhibitory concentration for Cutibacterium acnes isolates. This was the first study that determined clindamycin free concentrations in the prostatic fluid of rats. These findings suggest that clindamycin may be an effective alternative for the treatment of prostatitis caused by Cutibacterium acnes.