Infections Flashcards
What is cellulitis?
Acute, non-purulent spreading infection of the subcutaneous tissue and dermis, causing overlying skin inflammation.
What is erysipelas?
A form of superficial cellulitis involving the upper dermis and superficial lymphatics
What is the aetiology of cellulitis and erysipelas? (x4)
- Penetrating injury e.g., cannulation
- Local lesions such as insect bites
- Fissuring such as anal fissures
- Rarely, can arise spontaneously from blood-borne sources
What are the common causative organisms in cellulitis and erysipelas? (x2)
Streptococcus pyogenes and Staphylococcus aureus.
What are the risk factors in cellulitis and erysipelas? (x3)
Poor hygiene and poor vascularisation of tissue (e.g., diabetes mellitus, peripheral vascular disease). Toe-web abnormalities as this may lead to a fissure and subsequent site of entry for pathogens.
What is the epidemiology of cellulitis and erysipelas?
Very common.
What are the signs and symptoms of cellulitis? (x3) Where?
- Erythema, oedema, warm and tender with acute onset and rapidly spreading. It can be well-demarcated or have indistinct margins.
- Typically found on limbs.
- Vesicles, blisters and petechiae when severe
- Pyrexia due to systemic spread
What are the signs and symptoms of periorbital cellulitis?
Swollen eyelids and erythematous skin changes.
What are the signs and symptoms of orbital cellulitis?
Painful eye movements, visual impairment, exophthalmos.
What are the signs and symptoms of erysipelas? (x5) Where?
- Raised, WELL-DEFINED, tender, BRIGHT RED rash with acute onset and rapidly spreading
- Typically found on face as well as limbs
- Vesicles, blisters and petechiae when severe
- Peau d’orange caused by superficial oedema around hair follicles which remain attached to the dermis
- Pyrexia due to systemic spread
- Lymphadenopathy and lymphangitis (infection spreading up through lymphatic vessels)
What are the investigations for cellulitis and erysipelas?
- BLOOD: WCC is always high or low (if it is normal, it is probably not cellulitis or erysipelas), ESR/CRP raised. Take blood culture if systemically unwell
- SKIN SWAB: antibiotic sensitivity if systemically unwell
- SKIN ASPIRATION: antibiotic sensitivity if systemically unwell and there is a collection of fluid
How is cellulitis and erysipelas managed?
EMPIRICAL ANTIBIOTICS: flucloxacillin (oral in non-severe, IV if severe), then clarithromycin or doxycycline. Add vancomycin if suspected MRSA. If in face triangle, first-line is amoxicillin/clavulanate
What is meant by treating empirically?
Treating with best guess i.e. without knowing causative organism definitively.
What are the complications of cellulitis and erysipelas? (x6)
- Sepsis
- Chronic oedema in affected area where cellulitis or erysipelas has damaged lymphatic drainage
- Necrotising fasciitis – penetrates deeper
- Sloughing of overlying skin
- Meningitis (if in danger triangle)
- Cavernous sinus thrombosis (if in danger triangle)
What is cutaenous candidiasis?
Overgrowth of Candida resulting in red, itchy rash following penetration below surface of skin.
What is the aetiology of cutaneous candidiasis? (x2)
Candida naturally lives on skin, so infection occurs when the fungus penetrates the skin. This is common in areas where the skin is moist or warm (creases, axilla, groin). Immunocompromised individuals are also more susceptible.
What are the signs and symptoms of cutaneous candidiasis?
Red, itchy rash in folds of skin, causing the skin to become cracked and sore. Blisters and pustules may also occur.
What is molluscum contagiosum?
Cutaneous skin lesions caused by Molluscum contagiosum. Molluscum contagiosum is a pox virus (double stranded DNA)
What is the aetiology of molluscum contagiosum? (x3)
- MCV 1: seen in children and as a result of child-to-child skin contact or fomites
- MCV 2: sexually transmitted in adults
- MCV 3: rare subtype in any age group
What is the pathophysiology of molluscum contagiosum?
Virus infects keratinocytes (epidermal layer) and mucosa causing papular lesions. The virus induces abnormal keratinocyte growth. The epidermal collections of abnormal keratinocytes are called Henderson-Patterson bodies (microscopy). Despite the abnormal cellular growth, MCV does not cause dysplasia.
What is the disease course of molluscum contagiosum?
2-4 years in immunocompetent individuals.
What is the epidemiology of molluscum contagiosum: Age? Climate?
Highest incidence in children. Higher in tropical climates.
What are the signs and symptoms of molluscum contagiosum? (x4)
- LESIONS: appear as umbilicated (central depressions), pearl-like, smooth papules. Distribution is typically over chest and axilla in children, and groin in adults.
- Local erythema and swelling – called inflamed molluscum and typically a marker of immune response to the lesion
- Pruritus
- Coexistent atopic eczema
What are the investigations for molluscum contagiosum? (x2)
- CURETTAGE BIOPSY (ring-like blade to biopsy lesion): in diagnostic uncertainty
- HAEMATOXYLIN AND EOSIN STAINING: Henderson-Patterson bodies stain heavily
