W4 18 skin infections Flashcards
What are the functions of the skin?
Barrier to the outside world
Barrier to heat and water loss
Hormone production
What are the main layers of the epidermis? (PG200 IMG)
Stratum corneum
Granular layer
Spinous layer
Basal layer
Basement membrane
What is the stratum corneum?
The outer upper most layer of terminally differentiated squares that are being shed from the surface of the skin, manifesting scaling and dryness.
What is the basal layer responsible for?
Basal layer of basal keratinocytes, which is responsible for the regeneration of the epidermis above, over a period of around 30 days.
What happens as skin is shed?
Cells undergo terminal differentiation from bottom to top. They progressively flatten and are replaced as they move superiorly by the layers below.
What specialised structures are in the dermis and what do they do?
Eccrine gland, sweat duct, hair follicle etc all contribute to immune/host defence.
What various circulating tissue resident immune cells are there in the skin?
Lymphocytes, neutrophils, macrophages, dendritic cells, Langerhans cells
What is the cutaneous microbiome?
All the microorganisms within an individual and their genetic material. Varies across the body, eg by site moistness, oily, dryness etc.
What are the components of the microbial defence system by the skin?
Sweat glands - have salts, bicarbonates, AMPs, immunoglobulins, cytokines
Nerve activation
Dendritic cells, T cell activation, antigen presentation, cytokines, neutrophil chemotaxis
Sebaceous gland - triglycerides, wax and cholesterol esters, squalene, neuropeptides, cytokines
Sebum
Epidermal products - creaminess, AMPs, cytokines, complement
What factors can contribute to invasive disease and pathogenic infection?
Age - elderly might not heal as well; newborns might not have a fully developed cutaneous defence mechanisms
Eg eczema causes impaired barrier function in the skin
Immunosuppression
Diabetes contributing to wound healing
Risk factors for bacterial, fungal or viral skin infections?
Barrier dysfunction: eczema
Immunodeficiency and immunosuppression
Read through this lecture - pg202-209 images
Bacterial, viral and fungal infections
How are skin infections tested for?
Swabs - bacterial culture and viral PCR, may need blood cultures too
Scrapings - mycology, mainly for fungals, hair plucking if affecting hair
?Biopsy - skins for histology and mycobacterial culture
Blood tests - inflammatory markers
Imaging - is the infection superficial or subcutaneous, CT or MRI
How are skin infections treated?
Antimicrobials - topical/systemic
Local topical therapy, gel/cream/mouthwash
Systemic - tablets or IV
Antibacterial, antifungal or antiviral
