Skin & Soft Tissue Infection Flashcards
What are the microbiological components of normal skin flora? [6]
- Diphtheroid
- Corynebacteria
- Anaerobes
- (yeast)
- Staphylococci (S. aureus)
- Streptococci (A,B,C,G)
What can go wrong with skin flora? [4]
- Breach in the normal flora skin barrier invites pathogens to infect and they can spread throughout the deeper dermis and fat
- This causes the typical signs of inflammation locally at the side of the breach:
- Oedema
- Pain
- Erythema
- Warmth
- This local inflammation can be treated with oral antibiotics
- But it can progress into invasive disease → treated with IV antibiotics
What are the non-modifiable and modifiable general risk factors for cellulitis? [4]
- Non-modifiable:
- pregnancy,
- white Caucasian
- Modifiable:
- venous insufficiency,
- lymphoedema
What are the non-modifiable and modifiable local risk factors for cellulitis? [8]
- Non-modifiable:
- trauma,
- animal/insect bites,
- tattoos
- Modifiable:
- ulcers,
- eczema,
- athletes foot,
- burns,
- surgical
What features of cellulitis would warrant hospital admission? [7]
- Class III or IV
- Class II (Unless have OPAT facilities available)
- Severe or rapidly deteriorating cellulitis
- Very young (under 1 year of age) or frail
- Immunocompromised
- Facial cellulitis
- Suspected orbital or periorbital cellulitis (admit under ophthalmology)
List the differential diagnoses for cellulitis and the features of each differential [6]
-
Stasis dermatitis
- absence of pain
- absence of fever
- circumferential
- bilateral
-
Acute arthritis
- joint involvement
- pain on movement
-
Pyoderma gangrenosum
- ulcerations on legs
- history of inflammatory bowel disease (IBD)
-
Hypersensitivity/drug Rn
- exposure to allergens/drug
- pruritis
- absence of fever and pain
-
DVT
- Absence of skin changes or fever
-
Necrotising fasciitis
- severe pain out of proportion
- swelling
- fever
- rapid progression
- systemic toxicity
How do you differentiate between cellulitis and necrotising fasciitis? [5]
- Vital to rapidly differentiate from cellulitis:
- Initial PAIN, becoming PAINLESS
- RAPID spread
- SYSTEMICALLY unwell
- DUSKY skin and NECROSIS
- MAY have skin crepitus
What are the clinical manifestations of necrotising fasciitis? [8]
- Remarkably rapid progression
- Most common on the extremities e.g. legs
- Initially erythema and swelling without sharp margins
- Exquisite pain and tenderness
- Lymphatic involvement is rare
- Colour changes from red-purple to blue-grey
- Skin breakdown and bullae with development of anaesthesia
- Probing of the lesion reveals easy passage through the tissues
How is necrotising fasciitis managed? [7]
- Early suspicion + Surgical debridement
- 5 antibiotics used:
- Penicillin
- Flucloxacillin
- Clindamycin
- Gentamicin
- Metronidazole
- SURGERY is essential
Describe the typical appearance of erysipelas [4]
- Involves the upper dermis and superficial lymphatics
- Raised lesions with clear line of demarcation
- Classically butterfly involvement of the face but now accounts for only about 20% of cases.
- The legs are affected in up to 80% of cases.
Who typically gets erysipelas? [2]
affects infants + elderly
What are the microbiological causes of erysipelas? [1]
- usually group A strep,
- rarely: B, C, G and Staph aureus
- Elevated ASOT 10 days
How do you differentiate between erysipelas from cellulitis? [1]
erysipelas involves the ear but cellulitis does not
What is impetigo? [1]
Staphylococcal infection of epidermis
What is the typical appearance of impetigo? [2]
- often peri-oral
- “Honey coloured” crust
Who typically gets affected by impetigo? [3]
- Affects primarily children or sports persons
- Transmissible
How do you manage impetigo? [3]
- Remove crust gently
- Flucloxacillin
- Prevent secondary infection
What is the cause/pathogenesis of scarlet fever? [2]
- Results from infection with a streptococcal strain that elaborates streptococcal pyrogenic exotoxins or erythrogenic toxins
- Usually post pharyngitis but may complicate wound infections and post-partum infections
Describe the clinical presentation of scarlet fever [9]
- Diffuse red blush appears on the second day of infection, point of deeper red blanch on pressure
- Starts on the upper chest and spreads to the trunk, neck and extremities
- Occlusion of the sweat glands gives the skin a sandpapery touch
- Palms, soles and face are usually spared
- Circum-oral pallor
- White strawberry tongue, then red strawberry tongue
- Severe cases can be characterised by high fever and systemic toxicity
- Rash fades over the course of a week and desquamates over several weeks
- Mild eosinophilia in the early stages
What antibiotics are used to treate pasteurella infection caused by animal bites? [5]
- Penicillins (flucloxicillin much less active)
- Cephalosporins
- Tetracyclines
- Quinolones
- Macrolides
Describe soft tissue infections that occur following exposure to water including organisms [5], exposure cause [5] and features of the clinical syndrome [11] that each organism causes
- Aeromonas spp.
- due to exposure to fresh water
- clinical syndrome:
- rapidly developing infection associated with fever and sepsis
- Edwardsiella tarda
- due to exposure to fresh water
- clinical syndrome:
- cellulitis,
- occasionally fulminant infection with bacteraemia
- Erysipelothrix rhusiopathiae
- due to exposure to puncture wounds from crabs etc.
- clinical syndrome:
- indolent localised cutaneous eruption,
- erysipeloid
- Vibrio vulnificus
- due to exposure to salt or brackish water
- clinical syndrome:
- rapidly progressive necrotising infection,
- bullous cellulitis,
- sepsis
- Mycobacterium marinum
- due to exposure to fresh or salt water incl. fish tanks
- clinical syndrome:
- indolent infection,
- papules to ulcers,
- ascending lesions may resemble sporotrichosis
Define a burn [1]
damage to the skin (heat, chemical, radiation) causing protein denaturing
Describe how burns are classified, including the features of each type of classification [4]
- Superficial (1st)
- epidermis only
- dry/red
- blanches on pressure
- painful
- heals in 7 days
- Partial-thickness (2nd)
- epidermis and dermis
- superficial vs deep
- blisters
- typically painful
- heal <21days +/- antibiotics/surgery/grafting
- Full thickness
- to subcutaneous tissue
- painless
- non-blanching
- treated by surgery
- Fourth Degree
- reaching the fascia/muscle/bone
- healing requires surgery
Damage to skin due to burns compromises resistance to environment, hence this increases risk of…? [4]
- Infection
- Hypothermia
- Acid base abnormalities
- Dehydration
How should infected burns be managed? [5]
- Cleaning
- Dressings
- Topical antimicrobials (Gauzes/ointments/creams)
- (e.g. silver sulfadiazine, Bismuth-compounds, Chlorhexidine) — may impact healing
- Topical antibiotics (e.g. bacitracin)
- Systemic antibiotics, (directed by culture results), required in invasive infection
What are the features of cutaneous anthrax? [9]
- Surrounded by extensive oedema
- Painless and non-tender
- Black eschar
- Progresses over 2-6 days through papular, vesicular and ulcerated stages before eschar appears
- Affects hands, forearms, face and neck. Site of injection
- Discharge of serous fluid
- Local erythema and induration
- Local lymphadenopathy
- Associated with systemic malaise including headache, chills and sore throat; but afebrile.
What are the risk factors of cutaneous anthrax? [6]
- Working with animals or animal hides
- Making, owning or playing animal hide drums
- Drug use (particularly heroin use)
- Travel
- Working in postal sorting offices or handling large volumes of mail
- Received threatening letter or package containing white powder
What antibiotics are used to treat cutaneous anthrax? [5]
- Penicillin
- Flucloxacillin
- Clindamycin
- Ciprofloxacin
- Metronidazole
What is tinea? [2]
- Superficial dermatophyte infection characterized by scaly, inflammatory or non-inflammatory patches
- Generally limited to the epidermis and expands in a centrifugal pattern
How is tinea transmitted? [1]
via direct skin-to-skin contact
What are the symptoms of erythema infectiosum? [5]
- fever,
- headache,
- runny nose,
- followed by a pruritic rash on the face (“slapped cheek”), as well as the torso and extremities
What is hand-foot-and-mouth disease, what is the viral cause and who typically gets it? [3]
- Viral illness with oral and distal-extremity lesions
- Coxsackie virus A16
- typically affects children and infants
What are the symptoms of hand-foot-and-mouth disease? [6]
- fever
- rash
- headache
- sore throat
- oropharyngeal ulcers
- loss of appetite
What are the 2 types of presentations of herpes simplex virus? [2]
- stomatitis “cold sore”
- genital herpes
How do you treat herpes simplex virus (HSV)? [1]
acyclovir (topical, oral, IV)
What is shingles and how does it present? [2]
- Reactivation of dormant varicella zoster virus (VSV) (dorsal root ganglia)
- Dermatomal distribution
How do you treat shingles? [3]
- Treat only high-risk patients (immunocompromised, disseminated) with acyclovir
- Pain management:
- NSAIDs,
- gabapentin
