Infections of the Skin Flashcards
How does the skin act as a defensive barrier?
- epidermis - hard layer of dead cells
- dry surface
- constant sloughing
- acidic pH
- sweat
- rich blood and lymphatic supply
- produces antimicrobial substances - fatty acids, sebum, defensins
What does normal skin microbiota include?
- coagulate-negative staphylococci (staphylococcus epidermis, staphylococcus aureus)
- streptococcus pyogenes
- probionicbacterium acnes
- corynebacterium sp.
- candida sp.
Where do skin infections occur? (and examples)
> keratinised epithelium (ringworm) > epidermis (impetigo) > hair follicules (folliculitis) > subcutaneous fat (cellulitis) - fascia (necrotising fasciitis) - muscle (gas gangrene
What are the routes of skin infection?
- skin (pores, hair follicles)
- wounds
- bites
List bacterial infections of skin?
- staphylococcus aureus
- streptococcus pyogenes
- pseudomonas aeruginosa
- mycobacterium tuberculosis
What does toxic mediated mean?
bacteria produces toxins that produce illness
Features of streptococcus pyogenes?
- cocci morphology - round
- grows in chains
- gram positive
- group A strep - harmful
- multiple virulence factors
- beta haemolytic (breaks down RBCs)
Features of staphylococcus aureus?
- cocci morphology - round
- grows in clusters
- gram positive
- causes a huge range of illnesses
- antibiotic resistant strains - MRSA, VRSA
- multiple virulence factors
- diret infection or effect of toxin
Features of pseudomonas aeruginosa?
- coccobacillus morphology - between cocci and bacillus
- gram negative
- monotrichous flagellum - one
- opportunistic pathogen
- colonises catheters…
- produces exotoxin A
Macule skin lesion?
- flat
- red
- local inflammation
- blanches
Papule skin lesion?
- raised
- red
- more marked inflamation
Vesicle skin lesion?
- small blister
- fluid filled sac
Ulcer skin lesion?
- disruption of epithelium
Abscess?
collection of pus
Pyoderma?
pus-forming skin infection
- cutaneous access
Impetigo?
vesicles developing into rupturing pustules then forming dry crusts
Ecthyma?
rupturing vesicles leading to erythematous lesions and dried crusts
Furuncle?
boil, deep folliculitis, pus
Carbuncle?
collection of boils
Erysipelas?
erythema and inflammation of superficial dermis
Cellulitis?
erythematous inflamation affecting deeper dermis and subcutaneous fat
- rubor, calor, dolor, tumor
Acne?
infection of sebaceous follicles
Necrotising fasciitis?
cellulitis with necrosis affecting skin, deeper fascia and sometimes muscle
Dehiscence?
wound rupture along surgical suture
