Infections of the Skin Flashcards
Name the 3 routes of infection
Skin
Wounds
Bites
What is the role of commensal microbiota in and on the body ?
Commensal bacteria supply the host with essential nutrients and defend the host against opportunistic pathogens.
What skin infection occurs in the ‘keratinised epithelium’ ?
Ringworm
What skin infection occurs in the ‘epidermis’ ?
Impetigo
What skin infection occurs in the ‘hair follicles’ ?
Folliculitus
What skin infection occurs in the ‘subcutaneous fat’ ?
Cellulitis
What skin infection occurs in the ‘fascia’ ?
Necrotising fasciitis
What skin infection occurs in the ‘muscle’ ?
Gas gangrene
What is a skin lesion ?
A skin lesion refers to any skin area that has different characteristics from the surrounding skin, including color, shape, size, and texture.
What are the 2 classes of skin lesions ?
Primary
Secondary
What are primary skin lesions ?
Primary skin lesions originate on previously healthy skin and are directly associated with a specific cause.
Common examples of primary skin lesions include freckles, moles, and blisters, among others
Name the 6 different forms of primary skin lesions
Macule
Papule
Nodule
Vesicle
Bulla
Pustule
What are secondary skin lesions ?
Secondary skin lesions develop from the evolution of a primary skin lesion, either due to traumatic manipulation, such as scratching or rubbing, or due to its treatment or progression.
Name the 4 examples of secondary skin lesions
Scales
Crust
Fissure
Ulcer
Abscess
Collection of pus; pustule
Vesicle
Blister; bullae (plural); fluid filled sac
Pyoderma
Pus forming skin infection; cutaneous abscess
What does the pus in a pyoderma contain ?
Bacteria, White blood cells, Dead tissue and serum
Impetigo
Vesicles developing into ruptured pustules then forming dried crusts.
Caused by Gram + bacteria
Highly contagious
Ecthyma
Rupturing vesicles leading to erythematous lesions and dried crusts.
Folliculitis
Inflammation at hair follicle
Furuncle
Boil; deep foliculitis
Carbuncle
Collection of boils
Erysipelas
Erythema (redness) and inflammation of superficial dermis
Cellulitis
Erythematous inflammation affecting deeper dermis and subcutaneous fat
Acne
Infection of sebaceous follicles
Necrotising fasciitis
Cellulitis with necrosis affecting skin, deeper fascia and sometimes muscle
Dehiscence
Wound rupture along surgical suture
What are pathogenic bacteria ?
Pathogenic bacteria are bacteria that can cause disease.
Name the 5 key bacterial pathogens
Streptococcus pyogenes
Staphylococcus aureus
Pseudomonas aeruginosa
Mycobacterium tuberculosis
(Some may be toxin mediated)
Streptococcus pyogenes
Coccus
Grows in chains
Gram +
Group A Streptococcus
Multiple virulence factors
Beta-haemolytic
Staphylococcus aureus
Coccus
Grows in clusters
Gram +
Causes a huge range of illnesses
Antibiotic resistant strains (MRSA, VRSA)
Multiple direct virulence factors
Direct infection or effect of toxin
Pseudomonas aeruginosa
Coccobacillus
Gram -
Single flagellum, at one pole
Opportunistic
Colonises catheters
Produces exotoxin A
Which pathogenic bacteria colonises catheters ?
Pseudomonas aeruginosa
Where is impetigo usually found ?
Superficial - epidermis
Note : Ecthyma is a deep form of impetigo (goes into the dermis)
Management of spread of impetigo
Wash affected areas with soap and water
Wash hands regularly
Avoid scratching affected areas
Avoid sharing towels
What causes staphylococcal scalded skin syndrome ?
Severe, superficial blistering skin disorder.
Detachment of the epidermis
What is Staphylococcal Scalded Skin Syndrome also known as ?
Ritters disease
What is SSSS ?
Localised Staph A infection of the skin or upper respiratory tract.
Skin infections associated with the epidermis ?
Impetigo
Erysipelas (dermis as well- mainly)
Skin infections associated with the dermis ?
Necrotising fasciitis
Cellulitis
Erysipelas
Skin infections associated with the hypo-dermis ?
Necrotising fasciitis
Why are diabetics particularly susceptible to infections ?
High blood glucose can alter the normal microbiota
Reduced blood flow in the vasculature may result in problems in mobilising the immune system effectively
Neuropathy, particularly in the extremities, may result in increased injury
Injection with insulin provides a portal of entry
