Bacterial Skin Infections in Hospitalized Patients with Bullous Pemphigoid

Differentiation of keratinocytes or exposure to type 2 cytokines diminishes S. aureus internalization

Staphylococcus aureus is a leading cause of skin and soft tissue infections. Colonization by this bacterium is increased in individuals with chronic cutaneous diseases such as atopic dermatitis, psoriasis, and bullous pemphigoid. The greater abundance of S. aureus on the skin of subjects with atopic dermatitis in particular has been linked to recurrent cutaneous infections. The primary cell type of the epidermal layer of the skin is the keratinocyte, and it is thought that S. aureus internalized in keratinocytes associates with an increased incidence of skin infections. This study addresses whether keratinocyte differentiation and/or inflammation, two important characteristics altered in cutaneous diseases, influence bacterial internalization. To do this, S. aureus internalization was measured in immortalized and primary keratinocytes that were differentiated using high Ca2+-containing media and/or exposed to cytokines characteristic of atopic dermatitis (IL-4 and IL-13) or psoriasis (IL-17A and IL-22) skin. Our results indicate that S. aureus internalization is uniquely decreased upon keratinocyte differentiation, since this was not observed with another skin-resident bacterium, S. epidermidis. Additionally, treatment with IL-4 + IL-13 diminished bacterial internalization. We interpret this decrease as a mechanism of keratinocyte-based bacterial killing since a similar number of bacterial genomes were detected in cytokine-treated cells, but less viable internalized S. aureus was recovered. Finally, of the receptors reported for S. aureus binding/internalizing into keratinocytes, expression of the α5 component of the α5β1 integrin was in greatest accordance with the number of internalized bacteria in the context of keratinocyte differentiation.IMPORTANCEIndividuals with chronic cutaneous diseases demonstrate heightened susceptibility for severe and recurrent infections from Staphylococcus aureus. What drives this altered susceptibility remains poorly understood. Previous publications have detected S. aureus as deep as the dermal layer of skin in subjects with atopic dermatitis, suggesting that the cutaneous environment of this disease enables deeper bacterial infiltration than occurs in healthy individuals. This observation indicates that S. aureus has greater opportunity to interact with multiple skin cell types in individuals with chronic inflammatory skin diseases. Identifying the characteristics of the skin that influence bacterial internalization, a common method to establish reservoirs and evade the immune response, is critical for our understanding of S. aureus pathogenesis. The significance of this research is the novel identification of epidermal characteristics that influence S. aureus internalization. With this knowledge, methods can be developed to identify patient populations at greater risk for cutaneous infections.

Efficient epidermal delivery of antibiotics by self-assembled lecithin/chitosan nanoparticles for enhanced therapy on epidermal bacterial infections

The treatment for epidermal bacterial infections has become a primary healthy concern, producing a significant therapeutic challenge. Here we present a facile strategy to fabricate lecithin/chitosan nanoparticles (LCNPs) for efficient epidermal drug delivery over epidermal bacterial infections. The central rotatable composite design method was used for the optimization of the preparation, and that the optimal size (212.63 ± 1.95 nm) was obtained via analysis of variance (ANOVA). The prepared CIP-LCNPs show an average diameter of 325.9 ± 7.4 nm and a zeta potential of 26.6 ± 1.2 mV. Antibiotics can be well encapsulated in LCNPs and its release kinetics is studied with cumulative release of 93.81 ± 2.05 % for 48 h. The hemolytic activity, cytotoxicity, and skin irritation are further investigated. The zones of inhibition are 2.16 ± 0.04 cm and 2.92 ± 0.03 cm for Escherichia coli and Staphylococcus aureus, respectively. Moreover, in vitro permeation studies demonstrate that LCNPs can increase the accumulation of antibiotics in the epidermis with retention ratio 2-3 fold higher than commercial formulations. The in vivo result over epidermal-infected wound demonstrates the superior therapeutic effects of LCNPs. The developed LCNPs represent an important advance in fabricating therapeutic materials for enhanced therapy over epidermal bacterial infections.