Recent progress in the research aboutPropionibacterium acnesstrain diversity and acne: pathogen or bystander?

Skin barrier immunology from early life to adulthood

Our skin has a unique barrier function, which is imperative for the body's protection against external pathogens and environmental insults. Although interacting closely and sharing many similarities with key mucosal barrier sites, such as the gut and the lung, the skin also provides protection for internal tissues and organs and has a distinct lipid and chemical composition. Skin immunity develops over time and is influenced by a multiplicity of different factors, including lifestyle, genetics, and environmental exposures. Alterations in early life skin immune and structural development may have long-term consequences for skin health. In this review, we summarize the current knowledge on cutaneous barrier and immune development from early life to adulthood, with an overview of skin physiology and immune responses. We specifically highlight the influence of the skin microenvironment and other host intrinsic, host extrinsic (e.g. skin microbiome), and environmental factors on early life cutaneous immunity.

Sodium hyaluronates applied in the face affects the diversity of skin microbiota in healthy people

OBJECTIVE

A healthy and stable microbiome has many beneficial effects on the host, while an unbalanced or disordered microbiome can lead to various skin diseases. Hyaluronic acid is widely used in the cosmetics and pharmaceutical industries; however, specific reports on its effect on the skin microflora of healthy people have not been published. This study aimed to determine the effect of sodium hyaluronate on the facial microflora of healthy individuals.

METHODS

Face of 20 healthy female volunteers between 18 and 24 years was smeared with sodium hyaluronate solution once per day. Cotton swabs were used to retrieve samples on days 0, 14, and 28, and high-throughput sequencing of 16 S rRNA was used to determine the changes in bacterial community composition.

RESULTS

Facial application of HA can reduce the abundance of pathogenic bacteria, such as Cutibacterium and S. aureus, and increase the colonization of beneficial bacteria.

CONCLUSION

This is the first intuitive report to demonstrate the effect of hyaluronic acid on facial microflora in healthy people. Accordingly, sodium hyaluronate was found to have a positive effect on facial skin health.

C. acnes qPCR-Based Antibiotics Resistance Assay (ACQUIRE) Reveals Widespread Macrolide Resistance in Acne Patients and Can Eliminate Macrolide Misuse in Acne Treatment

Background

Macrolides have been widely used to treat moderate-to-severe acne for more than 50 years. However, the prevalent antibiotic resistance of Propionibacterium acnes, along with the absence of clinically available resistance tests, has made macrolide misuse a frequent occurrence around the globe, with serious consequences.

Objective

We developed Cutibacterium acnes quantitative PCR (qPCR)-based antibiotics resistance assay (ACQUIRE) to enable fast and accurate detection of C. acnes macrolide resistance in clinical settings, representing an opportunity to administer antibiotics more wisely and improve the quality of care.

Methods

A cross-sectional observational study (n = 915) was conducted to probe into the macrolide resistance of C. acnes in patients with acne.

Results

The high sensitivity of ACQUIRE enabled us to reveal a much higher C. acnes 23S recombinant DNA (rDNA) point mutation rate (52%) and thus a higher macrolide resistance (75.5%) compared to previous reports. Carriage of ermX gene was discovered on 472 (53%) subjects, which concurs with previous studies.

Conclusion

The macrolide resistance of C. acnes is much higher than previously reported. Integrating ACQUIRE into acne treatment modalities may eliminate macrolide misuse and achieve better clinical improvements.

Selective targeting of skin pathobionts and inflammation with topically applied lactobacilli

Tailored skin microbiome modulation approaches with probiotics are highly challenging. Here, we show that lactobacilli are underestimated members of the skin microbiota. We select specific strains of nomadic lactobacilli for their functional applicability on the skin and capacity to inhibit growth and inflammation by skin pathobionts. The strains are formulated as microcapsules for topical formulations and tested in patients with mild-to-moderate acne. The selected lactobacilli are able to reduce inflammatory lesions in a pilot and placebo-controlled study. Daily application for 8 weeks is associated with an in vivo temporary modulation of the microbiome, including a reduction in relative abundance of staphylococci and Cutibacterium acnes, and an increase in lactobacilli. The reduction in inflammatory lesions is still apparent 4 weeks after the topical application of the lactobacilli ended, indicating a possible additional immunomodulatory effect. This study shows that carefully selected and formulated lactobacilli are a viable therapeutic option for common acne lesions.

Porphyrins produced by acneic Cutibacterium acnes strains activate the inflammasome by inducing K+ leakage

Some Cutibacterium acnes subgroups dominate on healthy skin, whereas others are frequently acne associated. Here we provide mechanistic insights into this difference, using an anaerobic keratinocyte-sebocyte-C. acnes co-culture model. An acneic C. acnes strain as well as its porphyrins activates NRLP3 inflammasome assembly, whereas this was not observed with a non-acneic strain. Low levels of intracellular K⁺ in keratinocytes stimulated with extracted porphyrins or infected with the acneic strain were observed, identifying porphyrin-induced K⁺ leakage as trigger for inflammasome activation. Using a panel of C. acnes strains, we found that porphyrin production and IL-1β release are correlated and are higher in acneic strains. This demonstrates that the latter produce more porphyrins, which interact with the keratinocyte cell membrane, leading to K⁺ leakage, NLRP3 inflammasome activation, and IL-1β release and provides an explanation for the observation that some C. acnes strains are associated with healthy skin, whereas others dominate in acneic skin.

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We developed an anaerobic keratinocyte-sebocyte-C. acnes co-culture model

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Acneic C. acnes strains and their porphyrins activate NRLP3 inflammasome assembly

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Activation of the NRLP3 inflammasome is not observed in non-acneic strains

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Porphyrins from acneic C. acnes activate the inflammasome by inducing K⁺ leakage

Nonprescription acne vulgaris treatments: Their role in our treatment armamentarium-An international panel discussion

BACKGROUND

Acne vulgaris (acne), a common inflammatory skin disorder, has its peak incidence between 14 and 19 years of age, with girls frequently developing acne earlier than boys. Over recent years, persistent acne is becoming more prevalent in adult women.

OBJECTIVES

This review and panel discussion addresses challenges in acne management, particularly in adult women. The role which nonprescription acne treatment can play is explored when used as monotherapy or as an adjunctive treatment for acne of all severity.

METHODS

The best available evidence on nonprescription acne treatment was coupled with the opinion of an international expert panel of dermatologists to adopt statements and recommendations discussed in this review.

RESULTS

All severity of acne has a significant burden on patients. Addressing environmental factors that are important for the individual with acne may help to educate, prevent, effectively manage, and maintain acne, as per the panel. They agreed that the adult female acne population has unique needs because of their aging skin and social environment. Nonprescription acne treatment products may help to balance the efficacy and tolerability of prescription acne treatment. Currently, there are no specific guidelines for how to use nonprescription acne treatment products in these patients.

CONCLUSION

The panel agreed that guidelines including nonprescription acne treatment either as monotherapy for mild acne or in combination with prescription treatments for more severe acne would address a significant unmet need.

pH-Dependent Antibacterial Activity of Glycolic Acid: Implications for Anti-Acne Formulations

Glycolic acid is the smallest alpha hydroxy acid and widely used for skincare applications, including to treat acne vulgaris. Oftentimes, high concentrations of glycolic acid (~20–50 vol%) are incorporated into chemical peels to reduce acne-related inflammation while there is an outstanding need to determine to what extent glycolic acid can potently inhibit Cutibacterium acnes (formerly known as Propionibacterium acnes), which is a Gram-positive bacterium implicated in acne pathogenesis. Herein, we report that glycolic acid exhibits pH-dependent antibacterial activity against C. acnes and mechanistic studies identified that the nonionic form of glycolic acid is more active than the anionic form. The degree of antibacterial activity, including minimum bactericidal concentration (MBC), of glycolic acid was evaluated in the pH range of 3 to 4.5, and the greatest potency was observed at pH 3. In light of skincare formulation needs, we selected the pH 3.5 condition for further testing and determined that glycolic acid kills C. acnes cells by disrupting bacterial cell membranes. While most conventional treatments involve high concentrations of glycolic acid (>20%), our findings support the potential of developing anti-acne formulations with glycolic acid concentrations as low as 0.2% and with pH conditions that are suitable for over-the-counter applications.

Propionibacterium acnes-associated chronic hypertrophic pachymeningitis followed by refractory otitis media: a case report

BACKGROUND

Hypertrophic pachymeningitis (HP) is a rare disorder that involves localized or diffuse thickening of the dura mater. HP is associated with various inflammatory, infectious, and malignant diseases, such as rheumatic arthritis, sarcoidosis, anti-neutrophil cytoplasmic antibody-associated vasculitis, IgG4-related disorders, syphilis, tuberculosis, bacterial and fungal infections, cancer, and idiopathic diseases, when evaluation fails to reveal a cause. Among them, chronic infection with Propionibacterium acnes is a rare etiology of HP, and its pathology remains unclear.

CASE PRESENTATION

An 80-year-old man having refractory otitis media with effusion of the right ear presented with progressive right-sided headache and nausea. Post-contrast brain magnetic resonance imaging revealed right mastoiditis and remarkable thickening of the dura mater and enhancement of pia mater extending from the right middle cranial fossa to the temporal lobe. HP secondary to middle ear infection was suspected, and a biopsy of the right mastoid was performed. An anaerobic culture of the biopsied right mastoid showed the growth of P. acnes, and histopathological examination using P. acnes-specific monoclonal antibody (PAB antibody) revealed the infiltration of inflammatory cells with P. acnes. Moreover, using PAB antibody, P. acnes was detected in the biopsy specimen of the thickening dura mater. No granulomas were identified in either specimen. HP was resolved with long-term administration of antibiotics and steroids.

CONCLUSION

This is the first documentation of pathologically demonstrated chronic HP associated with P. acnes infection followed by refractory otitis media. This report showed that chronic latent P. acnes infection induces chronic inflammation.

The role of the skin microbiota in acne pathophysiology

BACKGROUND

The role of skin microbiota in acne remains to be fully elucidated. Initial culture-based investigations were hampered by growth rate and selective media bias. Even with less biased genomic methods, sampling, lysis and methodology, the task of describing acne pathophysiology remains challenging. Acne occurs in sites dominated by Cutibacterium acnes (formerly Propionibacterium acnes) and Malassezia species, both of which can function either as commensal or pathogen.

OBJECTIVES

This article aims to review the current state of the art of the microbiome and acne.

METHODS

The literature regarding the microbiome and acne was reviewed.

RESULTS

It remains unclear whether there is a quantitative difference in microbial community distribution, making it challenging to understand any community shift from commensal to pathogenic nature. It is plausible that acne involves (i) change in the distribution of species/strains, (ii) stable distribution with pathogenic alteration in response to internal (intermicrobe) or external stimuli (host physiology or environmental) or (iii) a combination of these factors.

CONCLUSIONS

Understanding physiological changes in bacterial species and strains will be required to define their specific roles, and identify any potential intervention points, in acne pathogenesis and treatment. It will also be necessary to determine whether any fungal species are involved, and establish whether they play a significant role. Further investigation using robust, modern analytic tools in longitudinal studies with a large number of participants, may make it possible to determine whether the microbiota plays a causal role, is primarily involved in exacerbation, or is merely a bystander. It is likely that the final outcome will show that acne is the result of complex microbe-microbe and community-host interplay.

Propionibacterium (Cutibacterium) acnes Bacteriophage Therapy in Acne: Current Evidence and Future Perspectives

Acne vulgaris is the most common dermatological disorder worldwide. It is a multifactorial disease that involves increased sebum production, hyperkeratinization of the pilosebaceous unit, Propionibacterium acnes (Cutibacterium acnes) colonization, and inflammation. The human skin microbiome hosts a wide variety of microorganisms, including bacteria, viruses, and fungi. A delicate balance of these microorganisms is essential for the barrier function of the skin. Propionibacterium acnes represents nearly 90% of the human skin microbiome of healthy adults. Acne is a chronic recurrent disease that requires long-lasting treatment, which has led to the emergence of antibiotic resistance. New alternatives to traditional therapy are emerging, including antimicrobial peptides, natural engineered antibodies, and bacteriophages. Bacteriophages have been shown to play a role in human skin health and disease. There is evidence supporting phage therapy in many types of skin infections. P. acnes bacteriophages have been isolated and characterized. However, only a few in vitro studies have tested the ability of bacteriophages to kill P. acnes. Furthermore, there is no evidence on bacteriophage therapy in the treatment of acne in humans. In this review, we summarize the most recent evidence regarding P. acnes bacteriophages and the potential role of these bacteriophages in the treatment of acne. Further research on this field will provide the evidence to use phage therapy to decrease rates of antibiotic resistance and restore antibiotic susceptibility of P. acnes.

Cutibacterium acnes (Propionibacterium acnes) and acne vulgaris: a brief look at the latest updates

While the commensal bacterium Propionibacterium acnes (P. acnes) is involved in the maintenance of a healthy skin, it can also act as an opportunistic pathogen in acne vulgaris. The latest findings on P. acnes shed light on the critical role of a tight equilibrium between members of its phylotypes and within the skin microbiota in the development of this skin disease. Indeed, contrary to what was previously thought, proliferation of P. acnes is not the trigger of acne as patients with acne do not harbour more P. acnes in follicles than normal individuals. Instead, the loss of the skin microbial diversity together with the activation of the innate immunity might lead to this chronic inflammatory condition. This review provides results of the most recent biochemical and genomic investigations that led to the new taxonomic classification of P. acnes renamed Cutibacterium acnes (C. acnes), and to the better characterisation of its phylogenetic cluster groups. Moreover, the latest data on the role of C. acnes and its different phylotypes in acne are presented, providing an overview of the factors that could participate in the virulence and in the antimicrobial resistance of acne-associated strains. Overall, this emerging key information offers new perspectives in the treatment of acne, with future innovative strategies focusing on C. acnes biofilms and/or on its acne-associated phylotypes.

Skin Immune Landscape: Inside and Outside the Organism

The skin is an essential organ to the human body protecting it from external aggressions and pathogens. Over the years, the skin was proven to have a crucial immunological role, not only being a passive protective barrier but a network of effector cells and molecular mediators that constitute a highly sophisticated compound known as the “skin immune system” (SIS). Studies of skin immune sentinels provided essential insights of a complex and dynamic immunity, which was achieved through interaction between the external and internal cutaneous compartments. In fact, the skin surface is cohabited by microorganisms recognized as skin microbiota that live in complete harmony with the immune sentinels and contribute to the epithelial barrier reinforcement. However, under stress, the symbiotic relationship changes into a dysbiotic one resulting in skin disorders. Hence, the skin microbiota may have either positive or negative influence on the immune system. This review aims at providing basic background information on the cutaneous immune system from major cellular and molecular players and the impact of its microbiota on the well-coordinated immune responses in host defense.

Diet-induced reconstruction of mucosal microbiota associated with alterations of epithelium lectin expression and regulation in the maintenance of rumen homeostasis

It is unknown whether lectins of the rumen epithelium contribute to the recognition of mucosal microbes and activation of tolerogenic cytokines in ruminant animals. We applied an integrated method of RNA-seq and 16S rRNA gene sequencing to investigate alterations of epithelial lectin expression and regulation with a diet-induced reconstruction of the mucosal microbiota in the goat rumen. Our results showed that the diversity and richness of the rumen mucosal microbiota were promoted by the dietary concentrate. Meantime, in the rumen epithelium, five lectin genes, namely, sialic acid-binding Ig-like lectin 14 (LOC102180073), C-type lectin domain family 4, member E (CLEC4E), C-type lectin domain family 7, member A (CLEC7A), C-type lectin domain family 16, member A (CLEC16A), and lectin, mannose-binding 2 (LMAN2), were indicated to promote the expression of 8 tolerogenic cytokines, transforming growth factor beta 1 (TGFB1) and 4 enzyme genes involved in retinoic acid biosynthesis via 6 signaling pathways. Analysis of the combined data showed that 9 microbial genera (Clostridium_IV, Desulfobulbus, Eubacterium, Ochrobactrum, Propionibacterium, Pseudomonas, Slackia, Staphylococcus and Subdivision5_genera_IS) were highly related to the expression of functional lectins. These findings provide new insights into the interactions between the rumen epithelium and mucosal microbiota in the maintenance of rumen homeostasis.

Edible Plants and Their Influence on the Gut Microbiome and Acne

Acne vulgaris affects most people at some point in their lives. Due to unclear etiology, likely with multiple factors, targeted and low-risk treatments have yet to be developed. In this review, we explore the multiple causes of acne and how plant-based foods and supplements can control these. The proposed causative factors include insulin resistance, sex hormone imbalances, inflammation and microbial dysbiosis. There is an emerging body of work on the human gut microbiome and how it mediates feedback between the foods we eat and our bodies. The gut microbiome is also an important mediator of inflammation in the gut and systemically. A low-glycemic load diet, one rich in plant fibers and low in processed foods, has been linked to an improvement in acne, possibly through gut changes or attenuation of insulin levels. Though there is much interest in the human microbiome, there is much more unknown, especially along the gut-skin axis. Collectively, the evidence suggests that approaches such as plant-based foods and supplements may be a viable alternative to the current first line standard of care for moderate acne, which typically includes antibiotics. Though patient compliance with major dietary changes is likely much lower than with medications, it is a treatment avenue that warrants further study and development.

Tropism and virulence of Cutibacterium (formerly Propionibacterium) acnes involved in implant-associated infection

The recognition of the pathogenicity of Cutibacterium acnes in implant-associated infection is not always obvious. In this paper, we aimed to distinguish pathogenic and non-pathogenic C. acnes isolates. To reach this goal, we investigated the clonal complex (CC) of a large collection of C. acnes clinical isolates through Multi-Locus Sequence Typing (MLST), we established a Caenorhabditis elegans model to assess C. acnes virulence and we investigated the presence of virulence factors in our collection. Ours results showed that CC36 and CC53 C. acnes isolates were more frequently observed in prosthetic joint infections (PJI) than CC18 and CC28 C. acnes isolates (p = 0.021). The C. elegans model developed here showed two distinct virulence groups of C. acnes (p < 0.05). These groups were not correlated to CC or clinical origin. Whole genome sequencing allowed us to identify a putative gene linked to low virulent strains. In conclusion, MLST remains a good method to screen pathogenic C. acnes isolates according to their clinical context but mechanisms of C. acnes virulence need to be assess thought transcriptomic analysis to investigate regulatory process.

A comparative study of Cutibacterium (Propionibacterium) acnes clones from acne patients and healthy controls

BACKGROUND

Cutibacterium (Propionibacterium) acnes is assumed to play an important role in the pathogenesis of acne.

OBJECTIVES

To examine if clones with distinct virulence properties are associated with acne.

METHODS

Multiple C. acnes isolates from follicles and surface skin of patients with moderate to severe acne and healthy controls were characterized by multilocus sequence typing. To determine if CC18 isolates from acne patients differ from those of controls in the possession of virulence genes or lack of genes conducive to a harmonious coexistence the full genomes of dominating CC18 follicular clones from six patients and five controls were sequenced.

RESULTS

Individuals carried one to ten clones simultaneously. The dominating C. acnes clones in follicles from acne patients were exclusively from the phylogenetic clade I-1a and all belonged to clonal complex CC18 with the exception of one patient dominated by the worldwide-disseminated and often antibiotic resistant clone ST3. The clonal composition of healthy follicles showed a more heterogeneous pattern with follicles dominated by clones representing the phylogenetic clades I-1a, I-1b, I-2 and II. Comparison of follicular CC18 gene contents, allelic versions of putative virulence genes and their promoter regions, and 54 variable-length intragenic and inter-genic homopolymeric tracts showed extensive conservation and no difference associated with the clinical origin of isolates.

CONCLUSIONS

The study supports that C. acnes strains from clonal complex CC18 and the often antibiotic resistant clone ST3 are associated with acne and suggests that susceptibility of the host rather than differences within these clones may determine the clinical outcome of colonization.