The skin barrier and microbiome in infantile atopic dermatitis development: can skin care prevent onset?

Atopic dermatitis (AD), a prevalent Th2-dominant skin disease, involves complex genetic and environmental factors, including mutations in the Filaggrin gene and dysbiosis of skin microbiota characterized by an increased abundance of Staphylococcus aureus. Our recent findings emphasize the pivotal role of the skin barrier's integrity and microbial composition in infantile AD and allergic diseases. Early skin dysbiosis predisposes infants to AD, suggesting targeted skincare practices as a preventive strategy. The effects of skincare interventions, particularly the application of moisturizers with the appropriate molar concentration of ceramides, cholesterol, and fatty acids, play a crucial role in restoring the skin barrier. Notably, our study revealed that appropriate skincare can reduce Streptococcus abundance while supporting Cutibacterium acnes presence, thus directly linking skincare practices to microbial modulation in neonatal skin. Despite the mixed outcomes of previous Randomized Controlled Trials on the efficacy of moisturizers in AD prevention, our research points to the potential of skincare intervention as a primary preventive method against AD by minimizing the impact of genetic and environmental factors. Furthermore, our research supports the notion that early aggressive management of eczema may reduce the incidence of food allergies, highlighting the necessity for multifaceted prevention strategies that address both the skin barrier and immune sensitization. By focusing on repairing the skin barrier and adjusting the skin's microbiome from birth, we propose a novel perspective on preventing infantile AD and allergic diseases, opening new avenues for future studies and practices in allergy prevention.

The role of Staphylococcus aureus quorum sensing in cutaneous and systemic infections.

BACKGROUND: Staphylococcus aureus is a leading cause of human bacterial infections worldwide. It is the most common causative agent of skin and soft tissue infections, and can also cause various other infections, including pneumonia, osteomyelitis, as well as life-threatening infections, such as sepsis and infective endocarditis. The pathogen can also asymptomatically colonize human skin, nasal cavity, and the intestine. S. aureus colonizes approximately 20-30% of human nostrils, being an opportunistic pathogen for subsequent infection. Its strong ability to silently spread via human contact makes it difficult to eradicate S. aureus. A major concern with S. aureus is its capacity to develop antibiotic resistance and adapt to diverse environmental conditions. The variability in the accessory gene regulator (Agr) region of the genome contributes to a spectrum of phenotypes within the bacterial population, enhancing the likelihood of survival in different environments. Agr functions as a central quorum sensing (QS) system in S. aureus, allowing bacteria to adjust gene expression in response to population density. Depending on Agr expression, S. aureus secretes various toxins, contributing to virulence in infectious diseases. Paradoxically, expressing Agr may be disadvantageous in certain situations, such as in hospitals, causing S. aureus to generate Agr mutants responsible for infections in healthcare settings. MAIN BODY: This review aims to demonstrate the molecular mechanisms governing the diverse phenotypes of S. aureus, ranging from a harmless colonizer to an organism capable of infecting various human organs. Emphasis will be placed on QS and its role in orchestrating S. aureus behavior across different contexts. SHORT CONCLUSION: The pathophysiology of S. aureus infection is substantially influenced by phenotypic changes resulting from factors beyond Agr. Future studies are expected to give the comprehensive understanding of S. aureus overall profile in various settings.

Physalin H, physalin B, and isophysalin B suppress the quorum-sensing function of Staphylococcus aureus by binding to AgrA.

The virulence of Staphylococcus aureus, including methicillin-resistant S. aureus (MRSA), depends on the expression of toxins and virulence factors controlled by the quorum-sensing (QS) system, encoded on the virulence accessory gene regulator (agr) locus. The aim of this study was to identify a phytochemical that inhibits Agr-QS function and to elucidate its mechanism. We screened 577 compounds and identified physalin H, physalin B, and isophysalin B--phytochemicals belonging to physalins found in plants of the Solanaceae family--as novel Agr-QS modulators. Biological analyses and in vitro protein-DNA binding assays suggested that these physalins suppress gene expression related to the Agr-QS system by inhibiting binding of the key response regulator AgrA to the agr promoters, reducing the function of hemolytic toxins downstream of these genes in MRSA. Furthermore, although physalin F suppressed gene expression in the Agr-QS system, its anti-hemolytic activity was lower than that of physalins H, B, and isophysalin B. Conversely, five physalins isolated from the same plant with the ability to suppress Agr-QS did not reduce bacterial Agr-QS activity but inhibited AgrA binding to DNA in vitro. A docking simulation revealed that physalin interacts with the DNA-binding site of AgrA in three docking states. The carbonyl oxygens at C-1 and C-18 of physalins, which can suppress Agr-QS, were directed to residues N201 and R198 of AgrA, respectively, whereas these carbonyl oxygens of physalins, without Agr-QS suppression activity, were oriented in different directions. Next, 100-ns molecular dynamics simulations revealed that the hydrogen bond formed between the carbonyl oxygen at C-15 of physalins and L186 of AgrA functions as an anchor, sustaining the interaction between the carbonyl oxygen at C-1 of physalins and N201 of AgrA. Thus, these results suggest that physalin H, physalin B, and isophysalin B inhibit the interaction of AgrA with the agr promoters by binding to the DNA-binding site of AgrA, suppressing the Agr-QS function of S. aureus. Physalins that suppress the Agr-QS function are proposed as potential lead compounds in the anti-virulence strategy for MRSA infections.