RESUMO
The healthy human epidermis provides physical protection and is impenetrable for pathogenic microbes. Nevertheless, commensal and pathogen bacteria such as Staphylococcus aureus are able to colonize the skin surface, which may subsequently lead to infection. To identify and characterize regulatory elements facilitating adaptation of S. aureus to the human skin environment we used ex vivo tissue explants and quantified S. aureus gene transcription during co-culture. This analysis provided evidence for a significant downregulation of the global virulence regulator agr upon initial contact with skin, regardless of the growth phase of S. aureus prior to co-culture. In contrast, the alternative sigma factor B (sigB) and the antimicrobial peptide-sensing system (graRS) were expressed during early colonization. Consistently, sigB target genes such as the clumping factor A (clfA) and fibrinogen and fibronectin binding protein A (fnbA) were strongly upregulated upon skin contact. At later timepoints of the adhesion process, wall teichoic acid (WTA) synthesis was induced. Besides the expression of adhesive molecules, transcription of molecules involved in immune evasion were increased during late colonization (staphylococcal complement inhibitor and staphylokinase). Similar to nasal colonization, enzymes involved in cell wall metabolism (sceD and atlA) were highly transcribed. Finally, we detected a strong expression of proteases from all three catalytic classes during the entire colonization process. Taken together, we here present an ex vivo skin colonization model that allows the detailed characterization of the bacterial adaptation to the skin environment.
RESUMO
BACKGROUND: Over the past years, it has become widely recognized that a proportion of chronic spontaneous urticaria (CSU) cases is of autoimmune origin, however, the search for reliable diagnostic tools to confirm underlying autoimmune pathophysiology is ongoing. The CD63 basophil activation test (CD63 BAT) has recently become useful for diagnosing autoimmune CSU. OBJECTIVES: To analyse the correlation between positive CD63 BAT results, total IgE antibody levels, and the presence of autoimmune thyroiditis as a comorbidity in patients diagnosed with CSU. MATERIALS AND METHODS: We performed a retrospective analysis of CD63 BAT results obtained from 87 CSU and 20 non-CSU patients. The information extracted from the patients' records included age, gender, total IgE levels, clinical history of autoimmune thyroiditis (AT), and the presence of anti-thyroid autoantibodies. RESULTS: Positive CD63 BAT results were significantly more frequent in CSU patients compared with non-CSU subjects (p=0.045). Furthermore, we found a strong significant negative correlation between the stimulation index (SI) value for CD63 BAT and total IgE levels in CD63 BAT-positive CSU patients (p=0.004; Spearman's rank correlation coefficient ρ=-0.322), meaning that higher SI values corresponded to lower total IgE values, and vice versa. CONCLUSION: The current standard set of diagnostic tools cannot be reliably used to determine when CSU is caused by autoimmune mechanisms. There is evidence that CD63 BAT represents a helpful diagnostic tool for detecting underlying autoimmunity. We show that high SI values in CD63 BAT-positive CSU patients correlate negatively with their total IgE levels. The clinical relevance of this effect needs to be investigated further.