Microbial dysbiosis in a mouse model of atopic dermatitis mimics shifts in human microbiome and correlates with the key pro-inflammatory cytokines IL-4, IL-33 and TSLP.

BACKGROUND: Cutaneous bacterial dysbiosis is a characteristic hallmark of atopic dermatitis (AD), and it decisively influences the severity of the disease. Despite this, frequently used murine models of AD have not been characterized regarding the changes in skin microbiome communities. OBJECTIVE: To analyse the skin microbiome of two frequently used murine models for AD for assessing their applicability in translational research. METHODS: AD was induced in mice by topical application of calcipotriol or oxazolone. Following comparable elicitation of AD-like dermatitis, including IgE induction, the skin microbial communities were analysed and compared with human AD. RESULTS: We detected critical differences in the microbiota composition of diseased skin. In contrast to calcipotriol treatment, application of oxazolone induced significant changes in the cutaneous microbiota and a drastic drop of bacterial richness. Furthermore, an expansion of Staphylococci, particularly S. xylosus, was observed in the oxazolone group, also displaying positive correlations with AD key markers including pH, TEWL, IL-4, TSLP and IL-33. CONCLUSIONS: In this article, we show that (a) the model of choice to investigate AD needs to be characterized for the cutaneous microbiota if applicable and (b) the oxazolone-mediated mixed Th1-Th2 immune response triggers microbiota-induced alterations which share similarities to dysbiosis in human AD and represents therefore a suitable model for translational research on AD if alterations of the microbiome are in the focus of the investigation.

[Microbiome, atopic eczema and blockade of type 2 immunity]. / Mikrobiom, atopisches Ekzem und Blockade der Typ-2-Immunität.

Atopic dermatitis affects roughly 20% of children and 3% of adults in Germany and other industrial countries, with an increasing prevalence. Its causality has still not been conclusively clarified but a type­2 T­helper cell mediated immunity reaction (type 2 immunity) dominates cutaneous inflammation. In the quest for the underlying pathogenic mechanisms and the development of improved prevention and treatment options, attention is also increasingly being paid to the influence of microbial colonization. This is facilitated by the rapid development of microbial analysis by sequencing. An increasing number of studies have shown that there is a link between disorders of the skin microbiome and the occurrence of atopic eczema and some also point towards the intestinal microbiome. In particular, a loss of diversity regarding the composition of the microbiome has been observed.

Efficacy of antifungal PACT in an in vitro model of onychomycosis.

BACKGROUND: The difficulty of antifungal substances to penetrate keratin and slow nail growth limit the efficacy of topical therapy in onychomycosis. One promising alternative is photodynamic antimicrobial chemotherapy, or PACT: an irradiated photosensitizer creates singlet oxygen molecules which destroy pathogens without damaging human cells. OBJECTIVE: As PACT has demonstrated strong antifungal capabilities, we wanted to investigate its efficacy in an in vitro model of onychomycosis. METHODS: PACT was tested in a microdilution assay, in an in vitro onychomycosis model as well as in a patient. RESULTS: PACT inhibited fungal growth in the microdilution assay with no colonies of T. rubrum detectable. Fungal growth was also inhibited in an onychomycosis model, after 30 min of LED irradiation. Subsequently, a patient with distolateral onychomycosis was treated on three consecutive days and showed significant and durable improvement of nail morphology 6 months after. CONCLUSION: PACT appears to be an effective treatment of onychomycosis in vitro. The promising results need to be validated by clinical trials.  

About the role and underlying mechanisms of cofactors in anaphylaxis.

Anaphylaxis is the systemic and most severe presentation of type I allergy. A number of conditions were identified that modulate the onset of anaphylaxis such as co- or augmentation factors, which significantly lower the allergen dose necessary for triggering anaphylaxis. Next to physical exercise or alcohol consumption, co-administration of nonsteroidal anti-inflammatory drugs (NSAID) or concomitant infectious diseases are well-documented cofactors of anaphylaxis. Registries for anaphylaxis document a role for cofactors in about 30% of anaphylactic reactions. Some disease entities such as 'wheat-dependent exercise-induced anaphylaxis' (WDEIA) are explicitly characterized by elicitation of anaphylaxis only in the presence of at least one such cofactor. Using WDEIA as a model disease, studies demonstrated that exercise increases skin prick test reactivity to and bioavailability of the allergen. Additional data indicate that alcohol consumption and NSAID administration display similar effects. Modulation of the cellular activation threshold is another mechanism underlying cofactor-induced anaphylaxis, most likely also functional when infectious diseases orchestrate elicitation of anaphylaxis. Cofactors are increasingly accepted to play a fundamental role in eliciting anaphylaxis. Consequently, to improve patient management modalities, a better understanding of the underlying mechanisms is warranted. This review aims to update clinicians and clinical scientists on recent developments.