The diversity and abundance of fungi and bacteria on the healthy and dandruff affected human scalp

Evaluation of novel cosmetic shampoo formulations against Malassezia species: Preliminary results of anti-dandruff shampoo formulations

OBJECTIVES

Malassezia species are common, clinically relevant, and lipid-dependent yeasts of humans. They are also the leading causes of the dandruff problem of humans, and the azoles are used primarily in their topical and systemic treatment. Resistance to azoles is an emerging problem among Malassezia sp., which indicates the need of new drug assessments that will be effective against dandruff and limit the use of azoles and other agents in treatment. Among them, the efficacy of various combinations of piroctone olamine and climbazole against Malassezia sp. is highly important. Here, we assessed the efficacies of various piroctone olamine and climbazole formulations against Malassezia sp. in comparison with ketoconazole.

METHODS

A total of nine formulations were included in the study, where each formulation was prepared from different concentrations of piroctone olamine and climbazole and both. All formulations contained the same ingredients as water, surfactants, hair conditioning agents, and preservatives. Malassezia furfur CBS1878, Malassezia globosa CBS7874, and Malassezia sympodialis CBS9570 were tested for antifungal susceptibility of each formulation by agar diffusion method. Sizes of the inhibition zones were compared with standard medical shampoo containing 2% ketoconazole, and the data were analyzed by Dunnett's multiple-comparison test.

RESULTS

For all Malassezia sp. strains, climbazole 0.5% and piroctone olamine/climbazole (0.1%/0.1% and 0.1%/0.5%) combinations were found to have the same effect as the medical shampoo containing 2% ketoconazole. Piroctone olamine/climbazole 1.0%/0.1% formulation showed the same efficacy as 2% ketoconazole on M. furfur and M. sympodialis, while 0.1%/0.5% formulation to only M. furfur. For M. globosa, none of the formulations tested were as effective as ketoconazole.

CONCLUSION

The species distribution of Malassezia sp. varies depending on the anatomical location on the host. According to the results of this study, climbazole and piroctone olamine combinations seem to be promising options against the dandruff problem with their high antifungal/anti dandruff efficacy.

Investigation of piroctone olamine delivery to the skin from single, binary and ternary solvent systems

OBJECTIVE

Disruption of the protective stratum corneum barrier increases the skin's vulnerability to microorganisms and facilitates conditions such as dandruff. Dandruff is a disorder of the scalp that causes increased scaling of the SC and is associated with Malassezia fungus. Consequently, many anti-dandruff commercial products use anti-fungal active ingredients such as piroctone olamine also known as Octopirox (OPX). OPX is an active ingredient used in a number of topical preparations for the management of dandruff. The characterization of the physicochemical properties of OPX was previously reported. The aim of the present work was to investigate a range of solvent systems for their effects on OPX interaction with human skin.

METHODS

The solvents used in this study were propylene glycol (PG), diethylene glycol monoethyl ether or Transcutol® (TC), PG monolaurate (PGML), isopropyl myristate (IPM), caprylic/capric triglyceride or Labrafac™ Lipophile WL 1349 (LAB), PG caprylate or Capryol® 90 (CAP), isostearyl isostearate (ISIS) and Plurol® Oleique CC 497 (PIOI). The single solvent systems evaluated were PG, TC, PGML, IPM, ISIS and CAP. For the binary solvent systems, PG and TC were examined. Ternary solvent systems consisted of: PG, TC and LAB; PG, PGML and LAB; and PG, TC and IPM. The concentration of OPX used was 1% (w/v). Heat-separated human epidermis was used for 24 h permeation experiments performed under finite dose conditions; mass balance studies were also conducted.

RESULTS

For the six single solvents examined no permeation was evident. Skin permeation of OPX was observed for binary and ternary solvent systems. The highest permeation for all PG:TC binary solvent system ratios tested was from the PG:TC (75:25) system. For the ternary solvent systems investigated, highest cumulative permeation of OPX was observed for PG:PGML:LAB (60:30:10). Considering all systems, PG:TC (75:25) delivered the greatest amount of OPX through the skin. Although OPX is deposited in the skin following the application of neat solvents, higher skin retention values were generally observed for binary and ternary systems.

CONCLUSION

To our knowledge, this is the first study to examine the permeation behaviour of OPX for a range of single, binary and ternary solvent systems.

Scalp microbiome composition changes and pathway evaluations due to effective treatment with Piroctone Olamine shampoo

OBJECTIVE

To characterize the scalp microbial composition, function, and connection to dandruff severity using a metagenomics approach and to understand the impact of a Piroctone Olamine containing anti-dandruff shampoo on the scalp microbiome.

METHODS

Shotgun metagenomics was used to characterize the composition of the scalp microbiomes from 94 subjects with and without clinically defined dandruff. Furthermore, the microbiome of the scalps of 100 dandruff sufferers before and after 3 weeks of treatment with either control or anti-dandruff shampoo containing 0.5% Piroctone Olamine (PO) was characterized and compared to identify microorganisms associated with the dandruff condition and the associated pathways and processes that may contribute to PO's effect on scalp microbiome.

RESULTS

A higher relative abundance of Malassezia restricta and Staphylococcus capitis and a lower abundance of Cutibacterium acnes were associated with the dandruff scalps relative to the no-dandruff scalps. A 3-week PO shampoo treatment reduced the relative abundance of Malassezia species and Staphylococcus capitis and increased the relative abundance of Cutibacterium acnes. This change to the scalp microbiome composition is consistent with a return to a healthy no-dandruff microbiome and improved clinical signs and symptoms as measured by adherent scalp flaking score (ASFS) compared with the control shampoo. Functional genomics analysis showed that the PO shampoo treatment reduced oxidative stress-associated genes and decreased the abundance of protease, urease, and lipase genes. These changes correlated positively to improvements in dandruff severity. PO treatment favourably shifted scalp microbiomes in dandruff subjects toward the no-dandruff state.

CONCLUSION

Our results suggest that part of the aetiology of dandruff can be attributed to dysbiosis of the scalp microbiome. PO treatment can restore a healthier microbiome, reducing oxidative stress and promoting better scalp health.

Efficacy of probiotics in hair growth and dandruff control: A systematic review and meta-analysis

Background

Probiotics are intellectually rewarding for the discovery of their potential as a source of functional food. Investigating the economic and beauty sector dynamics, this study conducted a comprehensive review of scholarly articles to evaluate the capacity of probiotics to promote hair growth and manage dandruff.

Methods

We used the PRISMA 2020 with Embase, Pubmed, ClinicalTrials.gov, Scopus, and ICTRP databases to investigate studies till May 2023. Meta-analyses utilizing the random effects model were used with odds ratios (OR) and standardized mean differences (SMD).

Result

Meta-analysis comprised eight randomized clinical trials and preclinical studies. Hair growth analysis found a non-significant improvement in hair count (SMD = 0.32, 95 % CI -0.10 to 0.75) and a significant effect on thickness (SMD = 0.92, 95 % CI 0.47 to 1.36). In preclinical studies, probiotics significantly induced hair follicle count (SMD = 3.24, 95 % CI 0.65 to 5.82) and skin thickness (SMD = 2.32, 95 % CI 0.47 to 4.17). VEGF levels increased significantly (SMD = 2.97, 95 % CI 0.80 to 5.13), while IGF-1 showed a non-significant inducement (SMD = 0.53, 95 % CI -4.40 to 5.45). For dandruff control, two studies demonstrated non-significant improvement in adherent dandruff (OR = 1.31, 95 % CI 0.13-13.65) and a significant increase in free dandruff (OR = 5.39, 95 % CI 1.50-19.43). Hair follicle count, VEGF, IGF-1, and adherent dandruff parameters were recorded with high heterogeneity. For the systematic review, probiotics have shown potential in improving hair growth and controlling dandruff through modulation of the immune pathway and gut-hair axis. The Wnt/β-catenin pathway, IGF-1 pathway, and VEGF are key molecular pathways in regulating hair follicle growth and maintenance.

Conclusions

This review found significant aspects exemplified by the properties of probiotics related to promoting hair growth and anti-dandruff effect, which serve as a roadmap for further in-depth studies to make it into pilot scales.

Fungal coexistence in the skin mycobiome: a study involving Malassezia, Candida, and Rhodotorula

Evidence of fungal coexistence in humans points towards fungal adaptation to the host environment, like the skin. The human commensal Malassezia has evolved, especially residing in sebum-rich areas of the mammalian body where it can get the necessary nutrition for its survival. This fungus is primarily responsible for skin diseases like Pityriasis versicolor (PV), characterized by hypo or hyperpigmented skin discoloration and erythematous macules. In this manuscript, we report a 19-year-old healthy female who presented with a one-year history of reddish, hypopigmented, asymptomatic lesions over the chest and a raised erythematous lesion over the face. Upon clinical observation, the patient displayed multiple erythematous macules and erythematous papules over the bilateral malar area of the face, along with multiple hypopigmented scaly macules present on the chest and back. Based on the above clinical findings, a diagnosis of PV and Acne vulgaris (AV) was made. Interestingly, the patient was immunocompetent and didn't have any comorbidities. Upon isolation of skin scrapings and post-culturing, we found the existence of three fungal genera in the same region of the patient's body. We further went on to confirm the identity of the particular species and found it to represent Malassezia, Rhodotorula, and Candida. We report how Malassezia, the predominant microbial resident skin fungus, coexists with other fungal members of the skin mycobiome. This study on an applied aspect of microbiology also shows how important it is to identify the fungal organism associated with skin infections so that appropriate therapeutics can be advised to avoid cases of relapse.

Microbiome: Role in Inflammatory Skin Diseases

As the body's largest organ, the skin harbors a highly diverse microbiota, playing a crucial role in resisting foreign pathogens, nurturing the immune system, and metabolizing natural products. The dysregulation of human skin microbiota is implicated in immune dysregulation and inflammatory responses. This review delineates the microbial alterations and immune dysregulation features in common Inflammatory Skin Diseases (ISDs) such as psoriasis, rosacea, atopic dermatitis(AD), seborrheic dermatitis(SD), diaper dermatitis(DD), and Malassezia folliculitis(MF).The skin microbiota, a complex and evolving community, undergoes changes in composition and function that can compromise the skin microbial barrier. These alterations induce water loss and abnormal lipid metabolism, contributing to the onset of ISDs. Additionally, microorganisms release toxins, like Staphylococcus aureus secreted α toxins and proteases, which may dissolve the stratum corneum, impairing skin barrier function and allowing entry into the bloodstream. Microbes entering the bloodstream activate molecular signals, leading to immune disorders and subsequent skin inflammatory responses. For instance, Malassezia stimulates dendritic cells(DCs) to release IL-12 and IL-23, differentiating into a Th17 cell population and producing proinflammatory mediators such as IL-17, IL-22, TNF-α, and IFN-α.This review offers new insights into the role of the human skin microbiota in ISDs, paving the way for future skin microbiome-specific targeted therapies.

Effect of two shampoo formulations on the prokaryotic and eukaryotic microbiota composition of the human scalp

OBJECTIVE

The human scalp is characterized by a moderately diverse microbial community, comprising prokaryotic (bacteria) and eukaryotic (fungi) members. Although the details are far from being fully understood, the human scalp microbiota is implicated in several scalp disorders, in particular dandruff formation. Hence, the protection of an intact and diverse scalp microbiota can be regarded as a quality criterion for hair and scalp care formulations. In this study, we investigated the influence of two commercially available, non-antimicrobial shampoo formulations on the structure of the scalp microbiota.

METHODS

Scalp microbiota samples, obtained by swab sampling from two cohorts of probands (n = 25, each), were analysed before and after daily use of two different shampoo formulations for 2 weeks, respectively. A polyphasic approach was used, comprising quantitative cultivation of bacteria and fungi on selective media as well as sequencing of PCR-amplified 16S rRNA and 18S rRNA genes, respectively.

RESULTS

All analyses revealed a microbiota composition typical for the human scalp. While in particular fungal germ numbers increased significantly during the treatments, overall bacterial and fungal community composition was not affected, based on alpha- and beta-diversity measures. However, we observed an increase in structural bacterial diversity with the age of the probands.

CONCLUSIONS

Over an application period of 2 weeks, the investigated shampoo induced quantitative but no qualitative changes in the scalp microbial community structure of the investigated probands, suggesting no adverse but rather preserving or even stimulating effects of the underlying formulations on the scalp microbiota. Further investigation will have to clarify if this is also true for longer application periods and if the formulations might affect community functionality, for example microbial gene expression, rather than community composition.

Modulating the skin mycobiome-bacteriome and treating seborrheic dermatitis with a probiotic-enriched oily suspension

Seborrheic dermatitis (SD) affects 2-5% of the global population, with imbalances in the skin microbiome implicated in its development. This study assessed the impact of an oily suspension containing Lactobacillus crispatus P17631 and Lacticaseibacillus paracasei I1688 (termed EUTOPLAC) on SD symptoms and the skin mycobiome-bacteriome modulation. 25 SD patients were treated with EUTOPLAC for a week. Symptom severity and skin mycobiome-bacteriome changes were measured at the start of the treatment (T0), after seven days (T8), and three weeks post-treatment (T28). Results indicated symptom improvement post-EUTOPLAC, with notable reductions in the Malassezia genus. Concurrently, bacterial shifts were observed, including a decrease in Staphylococcus and an increase in Lactobacillus and Lacticaseibacillus. Network analysis highlighted post-EUTOPLAC instability in fungal and bacterial interactions, with increased negative correlations between Malassezia and Lactobacillus and Lacticaseibacillus genera. The study suggests EUTOPLAC's potential as a targeted SD treatment, reducing symptoms and modulating the mycobiome-bacteriome composition.

Effects of a Postbiotic Saccharomyces and Lactobacillus Ferment Complex on the Scalp Microbiome of Chinese Women with Sensitive Scalp Syndrome

Introduction

Sensitive scalp is one of the most frequent complaints related to sensitive skin syndrome, characterized by unpleasant sensory reactions in the absence of visible signs of inflammation. In this study, the effects of topical application of postbiotic Himalaya-derived Saccharomyces and Lactobacillus ferment complex (SLFC) on the bacterial and fungal scalp microbiome at the taxonomic level and alleviation of sensitive skin syndrome were investigated.

Methods

Firstly, healthy female participants (aged 30-45) were classified into a healthy scalp group and a sensitive scalp group based on the questionnaire. Thereafter, topical application of SLFC on sensitive scalp as well as scalp microbiome was evaluated, with the difference in the distribution of microbial taxa between healthy and sensitive scalp communities was assessed using 16S rRNA and ITS1 sequencing analysis. In addition, the effect of SLFC on scalp microbiome at the species level for Cutibacterium acnes, Staphylococcus epidermidis, and Malassezia restricta was evaluated by the qPCR assessment.

Results

After treatment with SLFC for 28 days, the abundance of Staphylococcus, Lawsonella, and Fusarium in the sensitive scalp group was highly significantly increased (p < 0.001), while the abundance of Cutibacterium and Malassezia was highly significantly decreased (p < 0.001). Furthermore, the self-assessment questionnaire indicated a syndrome alleviation effect of 100% after 28 days with a twice-daily application of the SLFC.

Discussion

The obtained results would help to better understand the microbial community of the sensitive scalp and provide useful information on utilization of SLFC for maintaining a healthy scalp and modulating the scalp microbiome.

Bioprospecting the Skin Microbiome: Advances in Therapeutics and Personal Care Products

Bioprospecting is the discovery and exploration of biological diversity found within organisms, genetic elements or produced compounds with prospective commercial or therapeutic applications. The human skin is an ecological niche which harbours a rich and compositional diversity microbiome stemming from the multifactorial interactions between the host and microbiota facilitated by exploitable effector compounds. Advances in the understanding of microbial colonisation mechanisms alongside species and strain interactions have revealed a novel chemical and biological understanding which displays applicative potential. Studies elucidating the organismal interfaces and concomitant understanding of the central processes of skin biology have begun to unravel a potential wealth of molecules which can exploited for their proposed functions. A variety of skin-microbiome-derived compounds display prospective therapeutic applications, ranging from antioncogenic agents relevant in skin cancer therapy to treatment strategies for antimicrobial-resistant bacterial and fungal infections. Considerable opportunities have emerged for the translation to personal care products, such as topical agents to mitigate various skin conditions such as acne and eczema. Adjacent compound developments have focused on cosmetic applications such as reducing skin ageing and its associated changes to skin properties and the microbiome. The skin microbiome contains a wealth of prospective compounds with therapeutic and commercial applications; however, considerable work is required for the translation of in vitro findings to relevant in vivo models to ensure translatability.

Haze Exposure Changes the Skin Fungal Community and Promotes the Growth of Talaromyces Strains

Haze pollution has been a public health issue. The skin microbiota, as a component of the first line of defense, is disturbed by environmental pollutants, which may have an impact on human health. A total of 74 skin samples from healthy students were collected during haze and nonhaze days in spring and winter. Significant differences of skin fungal community composition between haze and nonhaze days were observed in female and male samples in spring and male samples in winter based on unweighted UniFrac distance analysis. Phylogenetic diversity whole-tree indices and observed features were significantly increased during haze days in male samples in winter compared to nonhaze days, but no significant difference was observed in other groups. Dothideomycetes, Capnodiales, Mycosphaerellaceae, etc. were significantly enriched during nonhaze days, whereas Trichocomaceae, Talaromyces, and Pezizaceae were significantly enriched during haze days. Thus, five Talaromyces strains were isolated, and an in vitro culture experiment revealed that the growth of representative Talaromyces strains was increased at high concentrations of particulate matter, confirming the sequencing results. Furthermore, during haze days, the fungal community assembly was better fitted to a niche-based assembly model than during nonhaze days. Talaromyces enriched during haze days deviated from the neutral assembly process. Our findings provided a comprehensive characterization of the skin fungal community during haze and nonhaze days and elucidated novel insights into how haze exposure influences the skin fungal community. IMPORTANCE Skin fungi play an important role in human health. Particulate matter (PM), the main haze pollutant, has been a public environmental threat. However, few studies have assessed the effects of air pollutants on skin fungi. Here, haze exposure influenced the diversity and composition of the skin fungal community. In an in vitro experiment, a high concentration of PM promoted the growth of Talaromyces strains. The fungal community assembly is better fitted to a niche-based assembly model during haze days. We anticipate that this study may provide new insights on the role of haze exposure disturbing the skin fungal community. It lays the groundwork for further clarifying the association between the changes of the skin fungal community and adverse health outcomes. Our study is the first to report the changes in the skin fungal community during haze and nonhaze days, which expands the understanding of the relationship between haze and skin fungi.

Compositional Variations between Adult and Infant Skin Microbiome: An Update

Human skin and its commensal microbiome form the first layer of protection to the outside world. A dynamic microbial ecosystem of bacteria, fungi and viruses, with the potential to respond to external insult, the skin microbiome has been shown to evolve over the life course with an alteration in taxonomic composition responding to altered microenvironmental conditions on human skin. This work sought to investigate the taxonomic, diversity and functional differences between infant and adult leg skin microbiomes. A 16S rRNA gene-based metataxonomic analysis revealed significant differences between the infant and adult skin groups, highlighting differential microbiome profiles at both the genus and species level. Diversity analysis reveals differences in the overall community structure and associated differential predicted functional profiles between the infant and adult skin microbiome suggest differing metabolic processes are present between the groups. These data add to the available information on the dynamic nature of skin microbiome during the life course and highlight the predicted differential microbial metabolic process that exists on infant and adult skin, which may have an impact on the future design and use of cosmetic products that are produced to work in consort with the skin microbiome.

Heat-killed Lacticaseibacillus paracasei GMNL-653 ameliorates human scalp health by regulating scalp microbiome

BACKGROUND

The equilibrium of the scalp microbiome is important for maintaining healthy scalp conditions, including sebum secretion, dandruff, and hair growth. Many different strategies to improve scalp health have been reported; however, the effect of postbiotics, such as heat-killed probiotics, on scalp health remains unclear. We examined the beneficial effects of heat-killed probiotics consisting of Lacticaseibacillus paracasei, GMNL-653, on scalp health.

RESULTS

Heat-killed GMNL-653 could co-aggregate with scalp commensal fungi, Malassezia furfur, in vitro, and the GMNL-653-derived lipoteichoic acid inhibited the biofilm formation of M. furfur on Hs68 fibroblast cells. The mRNA of hair follicle growth factors, including insulin-like growth factor-1 receptor (IGF-1R), vascular endothelial growth factor, IGF-1, and keratinocyte growth factor was up-regulated in skin-related human cell lines Hs68 and HaCaT after treatment with heat-killed GMNL-653. For clinical observations, we recruited 22 volunteer participants to use the shampoo containing the heat-killed GMNL-653 for 5 months and subsequently measured their scalp conditions, including sebum secretion, dandruff formation, and hair growth. We applied polymerase chain reaction (PCR) to detect the scalp microbiota of M. restricta, M. globosa, Cutibacterium acnes, and Staphylococcus epidermidis. A decrease in dandruff and oil secretion and an increase in hair growth in the human scalp were observed after the use of heat-killed GMNL-653-containing shampoo. The increased abundance of M. globosa and the decreased abundance of M. restricta and C. acnes were also observed. We further found that accumulated L. paracasei abundance was positively correlated with M. globosa abundance and negatively correlated with C. acnes abundance. S. epidermidis and C. acnes abundance was negatively correlated with M. globosa abundance and positively correlated with M. restricta. Meanwhile, M. globosa and M. restricta abundances were negatively associated with each other. C. acnes and S. epidermidis abundances were statistically positively correlated with sebum secretion and dandruff, respectively, in our shampoo clinical trial.

CONCLUSION

Our study provides a new strategy for human scalp health care using the heat-killed probiotics GMNL-653-containing shampoo. The mechanism may be correlated with the microbiota shift.

Chemical Composition and Antimicrobial Potential of a Plant-Based Substance for the Treatment of Seborrheic Dermatitis

Seborrheic dermatitis (SD) is the most prevalent dermatological disease, occurring in up to 50% of newborns, children, and adults around the world. The antibacterial and antifungal resistance contributed to the search for new natural substances and the development of a novel substance based on Melaleuca alternifolia (M. alternifolia) leaf oil (TTO), 1,8-cineole (eucalyptol), and α-(-)-bisabolol. Thus, this work aimed to determine the chemical composition of the novel plant-based substance and to evaluate its antimicrobial activity against standard microorganisms involved in the pathogenesis of SD. Moreover, the chemical composition of the substance was analyzed by gas chromatography coupled with mass spectrometry (GC/MS). Staphylococcus epidermidis (S. epidermidis), Staphylococcus aureus (S. aureus), Micrococcus luteus (M. luteus), and Candida albicans (C. albicans) were used for antimicrobial and antifungal assays by means of the broth microdilution method to determine the minimal inhibitory concentration (MIC). Finally, the substance’s ability to inhibit Malassezia furfur (M. furfur) was evaluated. Eighteen compounds from different chemical groups were identified by GC/MS. The major biologically active compounds of the substance were terpinen-4-ol (20.88%), 1,8-cineole (22.28%), (-)-α-bisabolol (25.73%), and o-cymene (8.16%). The results showed that the substance has a synergistic antimicrobial and antifungal activity, while S. epidermidis and C. albicans strains were the most susceptible. Furthermore, the substance inhibited M. furfur, which is a main pathogen involved in the pathogenesis of SD and clinical manifestations. It can be concluded that the novel plant-based substance has a promising potential against M. furfur and scalp commensal bacteria and may be helpful for the development of new drugs for treatment of dandruff and SD.

Malassezia restricta-mediated Lipoperoxidation: A Novel Trigger in Dandruff

Dandruff is a common scalp disorder with multiple microbial and host-related factors contributing to its aetiology, including alterations in scalp sebum. Despite existing evidence that the yeast Malassezia restricta plays a key role in the onset of dandruff, the interplay of these factors is poorly understood. Recently, squalene monohydroperoxide and malondialdehyde were established as biomarkers of dandruff-afflicted scalp, highlighting the role of sebum lipoperoxidation in the triggering and maintenance of dandruff, although its mechanism of action is unknown. The current study provides evidence that M. restricta mediates sebum peroxidation, leading to production of squalene monohydroperoxide and malondialdehyde. Furthermore, in vitro data show that these lipoperoxidation products act on epidermal cells and alter the skin barrier. These results support the role of Malassezia restricta-induced lipoperoxides as triggers of dandruff, which suggests that blocking their production could be a novel anti-dandruff treatment approach.

Review of the microbiome in skin aging and the effect of a topical prebiotic containing thermal spring water

BACKGROUND

Interest in the skin microbiome and the cosmetic benefits of probiotics, prebiotics, and postbiotics is increasing.

AIM

The current review explores the influence of the skin microbiome on facial skin aging and the effects of oral and topical probiotics, prebiotics, and postbiotics use on skin aging and cosmetic outcomes.

METHODS

Five dermatologists who treat clinical signs of facial skin aging and a microbiome scientist (advisors) explored the relationship between the skin microbiome and skin aging. Published evidence and the advisors' knowledge lead to guidance on the skin microbiome using oral and topical prebiotics, probiotics, and postbiotics to reduce signs of aging.

RESULTS

The role of the microbiome in aging skin is an emerging concept. A diverse skin microbiome is essential for skin health. Preliminary studies suggest oral probiotics and prebiotics may play a role in reducing signs of skin aging, likely through shifting to a greater skin and gut microbiome diversity. Thermal spring water contains probiotics and prebiotics. Preliminary studies suggest topically applied probiotics, prebiotics, and postbiotics may improve signs of skin aging, including a reduction in fine lines and increased hydration.

CONCLUSIONS

The panel agreed that oral and topical prebiotics, probiotics, and postbiotics may play a role in improving signs of aging by improving the skin microbiome. Larger studies with more prolonged treatment trials are needed to better understand the microbiome's role in skin aging and the possible benefits of prebiotics, probiotics, and postbiotics use.

Saccharide isomerate ameliorates cosmetic scalp conditions in a Chinese study population

BACKGROUND

Scalp conditions such as flaky or oily scalp affect people across ethnicities and age groups. In addition to flaking, increased sebum secretion, itching, and compromised scalp barrier function were described. Scalp conditions are aesthetically disturbing and may cause psychological distress in affected individuals who are looking for mild and effective treatment at the same time. Saccharide isomerate has a long history as a skin moisturizer, and it was found to improve skin barrier function, also suggesting possible beneficial effects on scalp.

AIMS

To provide relevant claim substantiation to introduce saccharide isomerate as a new scalp care active against scalp flaking condition.

MATERIAL AND METHODS

We conducted a placebo-controlled clinical study in an adult Chinese population affected by dandruff scalp as assessed by an adherent scalp flaking score. We monitored transepidermal water loss (TEWL), sebum secretion, and scalp flaking during 28 days.

RESULTS

Formulations containing Saccharide isomerate significantly improved all parameters both over time as well as compared to the placebo formulation.

CONCLUSION

We propose Saccharide isomerate for cosmetic formulations directed toward improving scalp conditions such as dandruff or oily scalp.

Comparative analysis of scalp and gut microbiome in androgenetic alopecia: A Korean cross-sectional study

Androgenetic alopecia (AGA) is a non-scarring and progressive form of hair loss occurring in both men and women. Although genetic predisposition and sex steroid hormones are the main causes, many factors remain unknown, and various extrinsic factors can negatively affect the lifespan of hair. We investigated skin-gut axis microorganisms as potential exogenous factors causing AGA, through comparative analyses of the scalp and gut microbiome in individuals with and without AGA in a Korean cohort. Using 16S rRNA gene sequencing, we characterized the scalp and gut microbiomes of 141 individuals divided into groups by sex and presence of AGA. Alpha diversity indices in the scalp microbiome were generally higher in individuals with AGA than in healthy controls. These indices showed a strong negative correlation with scalp-inhabitant bacteria (Cutibacterium and Staphylococcus), indicating that the appearance of non-inhabitant bacteria increases as hair loss progresses. No significant differences in diversity were observed between the gut microbiomes. However, bacterial functional differences, such as bile acid synthesis and bacterial invasion of epithelial cells, which are related to intestinal homeostasis, were observed. The networks of the scalp and gut microbiome were more complex and denser with higher values of the network topology statistic coefficient values (i.e., transitivity, density, and degree centrality) and more unique associations in individuals with AGA than in healthy controls. Our findings reveal a link between skin-gut microorganisms and AGA, indicating the former's potential involvement in the latter's development. Additionally, these results provide evidence for the development of cosmetics and therapeutics using microorganisms and metabolites involved in AGA.

Polygalaxanthone III, an Active Ingredient in Polygala japonica Houtt., Repaired Malassezia-Stimulated Skin Injury via STAT3 Phosphorylated Activation

Malassezia is a genus of commensal and lipid-dependent yeasts in human skin which also have a pathogenic lifestyle associated with several common skin disorders such as atopic dermatitis and eczema. Symptoms include red, itchy, and inflamed skin. We studied the growth characteristics and biochemical analyses of M. furfur which showed that the protein contents were greater in extracts taken at 24 h. These were then used to infect C57BL/6 mice, resulting in skin rupture. Polygalaxanthone III (POL), a more effective anti-inflammatory ingredient in Polygala japonica Houtt., was applied externally to the ulceration and successfully healed the wounds quickly. POL could not inhibit Malassezia activity as tested by the inhibition zone test, but affected the formation of lipid droplets in HaCaT cells. The wound-healing molecular mechanisms may be involved in the STAT3 pathway according to the Western blot results of skin tissues. Malassezia’s role in skin health is far from certain, and there is no clear solution, so understanding the development of Malassezia-associated skin diseases in general and seeking solutions are very important.

Infant Mode of Delivery Shapes the Skin Mycobiome of Prepubescent Children

Characterizing the skin mycobiome is necessary to define its association with the host immune system, particularly in children. In this study, we describe the skin mycobiome on the face, ventral forearm, and calf of 72 prepubescent children (aged 1 to 10 years) and their mothers, based on internal transcribed spacer (ITS) amplicon sequencing. The age and delivery mode at birth are the most influential factors shaping the skin mycobiome. Compared with that of the vaginally born children, the skin mycobiome of caesarean-born children is assembled by predominantly deterministic niche-based processes and exhibits a more fragile microbial network at all three sampling sites. Moreover, vaginal delivery leads to clearer intra- and interindividual specialization of fungal structures with increasing age; this phenomenon is not observed in caesarean-born children. The maternal correlation with children also differs based on the mode of delivery; specifically, the mycobiomes of vaginally born children at younger ages are more strongly correlated with vagina-associated fungal genera (Candida and Rhodotorula), whereas those of caesarean-delivered children at elder age include more skin-associated and airborne fungal genera (Malassezia and Alternaria). Based on this ecological framework, our results suggest that the delivery mode is significantly associated with maturation of the skin fungal community in children. IMPORTANCE Human skin is permanently colonized by microbes starting at birth. The hygiene hypothesis suggests that a lack of early-life immune imprinting weakens the body's resilience against atopic disorders later in life. To better understand fungal colonization following early-life periods affected by interruption, we studied the skin mycobiomes of 73 children and their mothers. Our results suggest a differentiation of the skin mycobiomes between caesarean-born and vaginally born children. Caesarean-born children exhibit a mycobiome structure with more fitted deterministic niche-based processes, a fragile network, and an unchanged microbial dissimilarity over time. In vaginally born children, this dissimilarity increases with age. The results indicate that initial microbial colonization has a long-term impact on a child's skin mycobiome. We believe that these findings will inspire further investigations of the "hygiene hypothesis" in the human microbiome, especially in providing novel insights into influences on the development of the early-life microbiome.

Comparative genomics of Staphylococcus capitis reveals species determinants

Staphylococcus capitis is primarily described as a human skin commensal but is now emergent as an opportunistic pathogen isolated from the bloodstream and prosthetic joint infections, and neonatal intensive care unit (NICU)-associated sepsis. We used comparative genomic analyses of S. capitis to provide new insights into commensal scalp isolates from varying skin states (healthy, dandruff lesional, and non-lesional), and to expand our current knowledge of the species populations (scalp isolates, n = 59; other skin isolates, n = 7; publicly available isolates, n = 120). A highly recombinogenic population structure was revealed, with genomes including the presence of a range of previously described staphylococcal virulence factors, cell wall-associated proteins, and two-component systems. Genomic differences between the two described S. capitis subspecies were explored, which revealed the determinants associated exclusively with each subspecies. The subspecies ureolyticus was distinguished from subspecies capitis based on the differences in antimicrobial resistance genes, β-lactam resistance genes, and β-class phenol soluble modulins and gene clusters linked to biofilm formation and survival on skin. This study will aid further research into the classification of S. capitis and virulence-linked phylogroups to monitor the spread and evolution of S. capitis.

Microbiota profiling on itchy scalp with undetermined origin

Scalp pruritus is a common skin problem that remains therapeutic challenge. The relationships between the dysbiosis of microbiota and skin diseases have caught attention recently. However, there are few reports about microbiota on itchy scalp. This study investigated scalp microbial characteristics of subjects with mild scalp pruritus of undetermined origin and preliminarily screened physiological factors and bacteria potentially related to pruritus. The pruritus severity of 17 qualified females was evaluated by Visual Analogue Scale (VAS). Microbiota collection was done at both itchy (n = 20) and non-itchy sites (n = 27) at occiput and crown of the same subject and Illumina sequencing was performed at the V3-V4 hypervariable regions of 16S rRNA. The corresponding sebum content, hydration, pH, trans-epidermal water loss, erythema index and porphyrin numbers were also measured by skin tester. We identified 3044 amplicon sequence variants from 821 genera. The itchy and non-itchy sites had different microbiota structures (p = 0.045, by multivariate analysis of variance), while there were large inter- and intra-individual variations. Both sites had Staphylococcus, Cutibacterium and Lawsonella as predominant genera, which were not significantly related to pruritus. The use of three genera Lactobacillus, Morganella and Pseudomonas, could well distinguish non-itchy from itchy groups, whereas different composition patterns existed inside each group. Our investigation indicated that though the bacterial community structure on itchy scalp was individual specific, there was difference between itchy and non-itchy sites. The study provides new insights into microbiota profiling on itchy scalp, which will help microbiota-targeted therapeutic experiment or products design for scalp pruritus.

Clinical Translation of Microbiome Research in Alopecia Areata: A New Perspective?

The continuous research advances in the microbiome field is changing clinicians’ points of view about the involvement of the microbiome in human health and disease, including autoimmune diseases such as alopecia areata (AA). Both gut and cutaneous dysbiosis have been considered to play roles in alopecia areata. A new approach is currently possible owing also to the use of omic techniques for studying the role of the microbiome in the disease by the deep understanding of microorganisms involved in the dysbiosis as well as of the pathways involved. These findings suggest the possibility to adopt a topical approach using either cosmetics or medical devices, to modulate or control, for example, the growth of overexpressed species using specific bacteriocins or postbiotics or with pH control. This will favour at the same time the growth of beneficial bacteria which, in turn, can impact positively both the structure of the scalp ecosystem on the host’s response to internal and external offenders. This approach, together with a “systemic” one, via oral supplementation, diet, or faecal transplantation, makes a reliable translation of microbiome research in clinical practice and should be taken into consideration every time alopecia areata is considered by a clinician.

Amplicon-based sequencing and co-occurence network analysis reveals notable differences of microbial community structure in healthy and dandruff scalps

Background

Dandruff is a chronic, recurring, and common scalp problem that is caused by several etiopathogeneses with complex mechanisms. Management of this condition is typically achieved via antifungal therapies. However, the precise roles played by microbiota in the development of the condition have not been elucidated. Despite their omnipresence on human scalp little is known about the co-occurrence/co-exclusion network of cutaneous microbiota.

Results

We characterized the scalp and hair surface bacterial and fungal communities of 95 dandruff-afflicted and healthy individuals residing in China. The degree distributions of co-occurrence/co-exclusion network in fungi-bacteria and bacteria-bacteria were higher in the healthy group (P < 0.0001), whereas the betweenness values are higher in the dandruff group (P < 0.01). Meanwhile, the co-occurrence/co-exclusion network among fungi-fungi and fungi-bacteria showed that compared to the healthy group, the dandruff group had more positive links (P < 0.0001). In addition, we observed that Malassezia slooffiae, Malassezia japonica and Malassezia furfur, were more abundant in the dandruff group than in the healthy group. These microbiota were co-exclusion by either multiple bacterial genera or Malassezia sp. in healthy group. The lactic acid bacteria on the scalp and hair surface, especially the genera Lactobacillus and Lactococcus, exhibit a negative correlation with multiple bacterial genera on the scalp and hair surface. Lactobacillus plantarum and Pediococcus lactis isolated on the healthy human scalp can inhibit the growth of Staphylococcus epidermidis in vitro.

Conclusions

We showed that microbial networks on scalp and hair surface with dandruff were less integrated than their healthy counterparts, with lower node degree and more positive and stronger links which were deemed to be unstable and may be more susceptible to environmental fluctuations. Lactobacillus bacteria have extensive interactions with other bacteria or fungi in the scalp and hair surface micro-ecological network and can be used as targets for improving scalp health.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08534-4.

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

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

Characterization of Distinct Microbiota Associated with Scalp Dermatitis in Patients with Atopic Dermatitis

Recent studies have focused on the role of skin microbiota in the pathogenesis of atopic dermatitis (AD). Among the various clinical phenotypes of AD, scalp dermatitis is a commonly observed clinical feature of AD. However, little is known about the pathogenesis of scalp dermatitis in AD. Hence, the aim of this study was to identify the distinct microbiota associated with scalp dermatitis in patients with AD. Using scalp swab samples from 10 patients with AD and 10 healthy controls, this study characterized the scalp microbiota in patients with AD via V3–V4 regions of the 16S rRNA gene sequencing for bacterial identification, and ITS2 gene sequencing for fungal identification. Among bacterial genera, Staphylococcus was the most abundant in AD than in healthy controls, whereas Cutibacterium was the most abundant species in the healthy controls. The most predominant scalp fungal microbiota was Malassezia both in AD and healthy controls, while a higher diversity of non-Malassezia fungi was observed in AD than in healthy controls. The study findings indicate the dysbiosis of scalp microbiota in AD and highlight the potential biomarker role of specific microbiota in AD on the scalp dermatitis.

Small molecules enhance the potency of natural antimicrobial peptides

The skin-associated microbiome plays an important role in general well-being and in a variety of treatable skin conditions. In this regard, endogenous antimicrobial peptides have both a direct and indirect role in determining the composition of the microbiota. We demonstrate here that certain small molecular species can amplify the antimicrobial potency of naturally occurring antimicrobial peptides. In this study, we have used niacinamide, a form of vitamin B3 naturally found in foods and widely used in cosmetic skincare products, and two of its structural analogs, to investigate their cooperativity with the human antimicrobial peptide LL37 on the bacterium Staphylococcus aureus. We observed a clear synergistic effect of niacinamide and, to some extent, N-methylnicotinamide, whereas isonicotinamide showed no significant cooperativity with LL37. Adaptively biased molecular dynamics simulations using simplified model membrane substrates and single peptides revealed that these molecules partition into the headgroup region of an anionic bilayer used to mimic the bacterial membrane. The simulated effects on the physical properties of the simulated model membrane are well correlated with experimental activity observed in real biological assays despite the simplicity of the model. In contrast, these molecules have little effect on zwitterionic bilayers that mimic a mammalian membrane. We conclude that niacinamide and N-methylnicotinamide can therefore potentiate the activity of host peptides by modulating the physical properties of the bacterial membrane, and to a lesser extent through direct interactions with the peptide. The level of cooperativity is strongly dependent on the detailed chemistry of the additive, suggesting an opportunity to fine-tune the behavior of host peptides.

Scalp Microbiome and Sebum Composition in Japanese Male Individuals with and without Androgenetic Alopecia

The skin microbiome and sebum may be associated with inflammation-related diseases of the scalp. To assess the pathogenesis and progression of androgenetic alopecia (AGA), we analyzed the composition of sebum and the bacterial and fungal microbiomes of the scalps of 118 Japanese male individuals with and without AGA, then discussed their roles in the pathogenesis of AGA. Sebum triglyceride and palmitic acid contents were higher in the AGA group than in the non-AGA group. Malassezia restricta, a lipophilic fungus that consumes palmitic acid, was abundant on the scalps of patients with AGA. Cutibacterium, Corynebacterium, and Staphylococcus were the most common genera in both groups, and patients with AGA exhibited scalp dysbiosis (increased abundance of Cutibacterium and decreased abundance of Corynebacterium). Our findings suggest that both sebum and the bacterial and fungal microbiomes of the scalp may be involved in the development of AGA.

Features of the Skin Microbiota in Common Inflammatory Skin Diseases

Many relatively common chronic inflammatory skin diseases manifest on the face (seborrheic dermatitis, rosacea, acne, perioral/periorificial dermatitis, periocular dermatitis, etc.), thereby significantly impairing patient appearance and quality of life. Given the yet unexplained pathogenesis and numerous factors involved, these diseases often present therapeutic challenges. The term “microbiome” comprises the totality of microorganisms (microbiota), their genomes, and environmental factors in a particular environment. Changes in human skin microbiota composition and/or functionality are believed to trigger immune dysregulation, and consequently an inflammatory response, thereby playing a potentially significant role in the clinical manifestations and treatment of these diseases. Although cultivation methods have traditionally been used in studies of bacterial microbiome species, a large number of bacterial strains cannot be grown in the laboratory. Since standard culture-dependent methods detect fewer than 1% of all bacterial species, a metagenomic approach could be used to detect bacteria that cannot be cultivated. The skin microbiome exhibits spatial distribution associated with the microenvironment (sebaceous, moist, and dry areas). However, although disturbance of the skin microbiome can lead to a number of pathological conditions and diseases, it is still not clear whether skin diseases result from change in the microbiome or cause such a change. Thus far, the skin microbiome has been studied in atopic dermatitis, seborrheic dermatitis, psoriasis, acne, and rosacea. Studies on the possible association between changes in the microbiome and their association with skin diseases have improved the understanding of disease development, diagnostics, and therapeutics. The identification of the bacterial markers associated with particular inflammatory skin diseases would significantly accelerate the diagnostics and reduce treatment costs. Microbiota research and determination could facilitate the identification of potential causes of skin diseases that cannot be detected by simpler methods, thereby contributing to the design and development of more effective therapies.

A folliculocentric perspective of dandruff pathogenesis: Could a troublesome condition be caused by changes to a natural secretory mechanism?

Dandruff is a common scalp condition, which frequently causes psychological distress in those affected. Dandruff is considered to be caused by an interplay of several factors. However, the pathogenesis of dandruff remains under-investigated, especially with respect to the contribution of the hair follicle. As the hair follicle exhibits unique immune-modulatory properties, including the creation of an immunoinhibitory, immune-privileged milieu, we propose a novel hypothesis taking into account the role of the hair follicle. We hypothesize that the changes and imbalance of yeast and bacterial species, along with increasing proinflammatory sebum by-products, leads to the activation of immune response and inflammation. Hair follicle keratinocytes may then detect these changes in scalp microbiota resulting in the recruitment of leukocytes to the inflammation site. These changes in the scalp skin immune-microenvironment may impact hair follicle immune privilege status, which opens new avenues into exploring the role of the hair follicle in dandruff pathogenesis. Also see the video abstract here: https://youtu.be/mEZEznCYtNs.

Sociodemographic characteristics and spectrum of Malassezia species in individuals with and without seborrhoeic dermatitis/dandruff: A comparison of residents of the urban and rural populations

Seborrhoeic dermatitis/dandruff (SD/D) is a common, persistent, relapsing inflammatory condition affecting the areas rich in sebaceous glands. SD/D is widely prevalent in India but Malassezia species implicated are not well studied. To estimate the prevalence and spectrum of Malassezia species causing SD/D and understand the sociodemographic characteristics of SD/D in rural and urban populations, a total of 200 SD/D patients and 100 healthy controls (HC) from both rural and urban backgrounds were enrolled in this study. SD/D severity was clinically graded as mild, moderate, severe, and very severe. The isolates were identified by phenotypic characters and confirmed by ITS2 PCR-RFLP and sequencing of the ITS region of rDNA. Severe (59%) and very severe (71%) form of SD/D was higher in the rural population compared to the urban population (P = .004). The isolation rate of Malassezia was significantly higher in overall SD/D patients scalp (82%) compared to HC (67%) (P = .005). From the scalp of SD/D patients, M. globosa (36.2%) was predominantly isolated followed by M. restricta (31.3%), M. furfur (15.7%), a mixture of M. globosa and M. restricta (12%) or M. arunalokei (4.8%). Similarly, M. globosa (49.3%) was predominately isolated from the scalp of HC followed by M. restricta (22.4%). M. restricta was significantly higher in the scalp of SD/D patients compared to HC and/or nasolabial fold of both SD/D patients and HC (P = .0001). Our findings indicate that M. restricta has a high association with SD/D. More severe disease frequency was observed in the rural population.

PRECIS

Dandruff is associated with Malassezia restricta and very severe cases are higher in rural population, probably due the poor hygiene. Moderate to severe hair loss and itching were strongly associated with dandruff. Use of soaps to cleanse scalp appears to be better than shampoo in preventing dandruff.

Skin microbiome alterations in seborrheic dermatitis and dandruff: A systematic review

Seborrheic dermatitis (SD) and dandruff (DF) are common chronic inflammatory skin diseases characterized by recurrent greasy scales, sometimes with erythema and itchiness. Although the exact pathophysiology of the disease is still unclear, current theories highlight the role of microbes on the skin surface in the pathogenesis of SD. Here, we conducted a systematic review to investigate the skin microbiome alterations in patients with SD/DF. We searched Medline/PubMed, Embase and Web of Science for research studies published in English between 1 January 2000 and 31 December 2020. A total of 12 studies with 706 SD/DF samples and 379 healthy samples were included in this study. The scalp and face were predominated by the fungi of Ascomycota and Basidiomycota and the bacteria of Actinobacteria and Firmicutes. In general, the included studies demonstrated an increased Malassezia restricta/Malassezia globosa ratio and a reduction in the Cutibaterium/Staphylococcus ratio in the setting of SD/DF. Staphylococcus was associated with epidermal barrier damage, including elevated levels of trans-epidermal water loss and pH, while Cutibacterium had a positive correlation with water content. Malassezia was also found to be related to an increased itching score and disease severity. Further studies focusing on the interactions between various microbes and the host and microbes can help us to better understand the pathogenesis of SD/DF.

Continuous clinical improvement of mild-to-moderate seborrheic dermatitis and rebalancing of the scalp microbiome using a selenium disulfide-based shampoo after an initial treatment with ketoconazole

OBJECTIVE

Scalp seborrheic dermatitis (SD) is a chronic, relapsing, and inflammatory scalp disease. Studies indicate a global bacterial and fungal microbiota shift of scalp SD, as compared to healthy scalp. Ketoconazole and selenium disulfide (SeS₂ ) improve clinical signs and symptoms in both scalp dandruff and SD.

AIM

The main objective of this study was to investigate the changes in the scalp microbiota diversity and counts in subjects with scalp SD during a two-phase treatment period.

MATERIAL AND METHODS

The scalp microbiota and clinical efficacy were investigated in 68 subjects with mild-to-moderate scalp SD after an initial one-month treatment with 2% ketoconazole, and after a 2-month maintenance phase, either with a 1% SeS₂ -based shampoo or its vehicle.

RESULTS

Thirty one subjects in the active and 37 subjects in the vehicle group participated. Ketoconazole provided an improvement of clinical symptoms (adherent (-1.75 p < 0.05), non-adherent (-1.5, p < 0.05)) flakes and erythema (scores 1.67-0.93, p < 0.001), in an increased fungal diversity and in a significant (p < 0.005) decrease of Malassezia spp. SeS₂ provided an additional clinical improvement (-0.8; p = 0.0002 and -0.7; p = 0.0081 for adherent and non-adherent flakes, respectively, at Day 84) compared to the vehicle associated with a low Malassezia spp. count and an additional significant (p < 0.001) decrease of the Staphylococcus spp. level.

CONCLUSION

Selenium disulfide provides an additional benefit on the scalp microbiota and in clinical symptoms of SD and dandruff after treatment with ketoconazole. The results confirm the role of Staphylococcus spp. in scalp SD and open possible perspectives for preventing relapses.

In-vivo impact of common cosmetic preservative systems in full formulation on the skin microbiome

Preservatives play an essentially role in ensuring that cosmetic formulations remain safe for use via control of microbial contamination. Commonly used preservatives include organic acids, alcohols and phenols and these play an essential role in controlling the growth of bacteria, fungi and moulds in substrates that can potentially act as a rich food source for microbial contaminants. Whilst the activity of these compounds is clear, both in vitro and in formulation, little information exists on the potential impact that common preservative systems, in full formulation, have on the skin's resident microbiome. Dysbiosis of the skin's microbiome has been associated with a number of cosmetic conditions but there currently are no in vivo studies investigating the potential for preservative ingredients, when included in personal care formulations under normal use conditions, to impact the cutaneous microbiome. Here we present an analysis of four in vivo studies that examine the impact of different preservation systems in full formulation, in different products formats, with varying durations of application. This work demonstrates that despite the antimicrobial efficacy of the preservatives in vitro, the skin microbiome is not impacted by preservative containing products in vivo.

Exploring the human hair follicle microbiome

Human hair follicles (HFs) carry complex microbial communities that differ from the skin surface microbiota. This likely reflects that the HF epithelium differs from the epidermal barrier in that it provides a moist, less acidic, and relatively ultraviolet light-protected environment, part of which is immune-privileged, thus facilitating microbial survival. Here we review the current understanding of the human HF microbiome and its potential physiological and pathological functions, including in folliculitis, acne vulgaris, hidradenitis suppurativa, alopecia areata and cicatricial alopecias. While reviewing the main human HF bacteria (such as Propionibacteria, Corynebacteria, Staphylococci and Streptococci), viruses, fungi and parasites as human HF microbiome constituents, we advocate a broad view of the HF as an integral part of the human holobiont. Specifically, we explore how the human HF may manage its microbiome via the regulated production of antimicrobial peptides (such as cathelicidin, psoriasin, RNAse7 and dermcidin) by HF keratinocytes, how the microbiome may impact on cytokine and chemokine release from the HF, and examine hair growth-modulatory effects of antibiotics, and ask whether the microbiome affects hair growth in turn. We highlight major open questions and potential novel approaches to the management of hair diseases by targeting the HF microbiome.

Skin microbiome transplantation and manipulation: Current state of the art

Many skin conditions are associated with an imbalance in the skin microbiome. In recent years, the skin microbiome has become a hot topic, for both therapeutic and cosmetic purposes. The possibility of manipulating the human skin microbiome to address skin conditions has opened exciting new paths for therapy. Here we review the skin microbiome manipulation strategies, ranging from skin microbiome transplantation, over skin bacteriotherapy to the use of prebiotics, probiotics and postbiotics. We summarize all efforts undertaken to exchange, manipulate, transplant or selectively apply the skin microbiome to date. Multiple microbial groups have been targeted, since they have been proven to be beneficial for skin health. We focus on the most common skin disorders and their associated skin microbiome dysbiosis and we review the existing scientific data and clinical trials undertaken to combat these skin conditions. The skin microbiome represents a novel platform for therapy. Transplantation of a complete microbiome or application of single strains has demonstrated beneficial therapeutic application.

Comparative antidandruff efficacy of plant extracts prepared from conventional and supercritical fluid extraction method and chemical profiling using GCMS

BACKGROUND

To combat dandruff associated pathogens, supercritical fluid extraction (SFE) can be used as an alternative eco-friendly technique to obtain antimicrobial plant extracts over conventional methods.

OBJECTIVES

The purpose of the study was to compare the yield and antimicrobial potential of extracts obtained by different extraction methods.

METHODS

Extraction was carried out by cold percolation method using ethyl acetate (EA) and SFE using CO₂. Antimicrobial activity was studied against dandruff causing microbes; Malassezia furfur, Propionibacterium acne, and Staphylococcus epidermidis by agar well diffusion and micro broth dilution method. Statistical evaluation was done by principal component analysis (PCA).

RESULTS

The yield was found higher in the ethyl acetate extracts. PCA indicated that among the sixteen extracts, SFE extract of Azadirachta indica leaves was the most influential with the highest F1 score and maximum antimicrobial activity. Cinnamomum zeylanicum SFE extract demonstrated the lowest MIC against P. acne and M. furfur. GC-MS analysis of A. indica extract inferred that ganoderic acid, 13,14-epoxyoleanan-3-ol acetate, henicosanal, 2-heptadecycloxirane were the major phytoconstituents whereas cinnamaldehyde, α- muurolene and caffeic acid were primarily found in cinnamon.

CONCLUSION

Bioactive compounds identified in the extracts of A. indica and C. zeylanicum can be used in natural antidandruff products.