Skin and soft tissue infections Flashcards by Pete McEwan

What is impetigo?

Superficial skin infection - multiple vesicular lesions on an erythematous base

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What is the peak age for impetigo?

2-5 years age

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What are predisposing factors for impetigo?

Skin abrasions
Minor trauma
Burns
Poor hygiene
Insect bites
Chickenpox
Eczema
Atopic dermatitis

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How is impetigo treated?

Topical antibiotics

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What is erysipelas?

Infection of the upper dermis - painful red area, associated fever, regional lymphadenopathy, elevated borders

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What is the most common causative organism for erysipelas?

Strep pyogenes

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What is cellulitis?

Diffuse skin infection involving deep dermis and subcutaneous fat

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What are features of cellulitis?

Presents as spreading erythematous area with no distinct borders
Fever
Regional lymphadenopathy
Possible source of bacteraemia

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What are common causative organisms of cellulitis?

Strep pyogenes

Staph aureus

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What are predisposing factors for cellulitis?

Diabetes mellitus
Tinea pedis
Lymphoedema

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How is cellulitis treated?

Combination of anti-staphylococcal and anti-streptococcal antibiotics

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What are hair-associated infections?

Folliculitis
Furunculosis
Carbuncles

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What is folliculitis?

Circumscribed pustular infection of a hair follicle

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Where is folliculitis typically found?

Head
Back
Buttocks
Extremities

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What is the most common causative organism for folliculitis?

Staph aureus

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What is furunculosis?

Single hair follicle-associated inflammatory nodule extending into dermis and subcutaneous tissue

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What are common affected areas of furunculosis?

Moist, hairy, friction prone areas - face, axilla, neck, buttocks

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What are risk factors for furunculosis?

Obesity
Diabetes mellitus
Atopic dermatitis
Chronic kidney disease
Corticosteroid use

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What is carbuncle?

When infection extends to multiple furuncles

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Where are carbuncles located?

Back of neck
Posterior trunk
Thigh

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How are hair associated infections treated?

Folliculitis - none/topical antibiotics
Furunculosis - none/topical antibiotics, if no improvement oral antibiotics
Carbuncles - hospital admission, surgery, IV antibiotics

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What are predisposing factors for necrotising fasciitis?

Diabetes mellitus
Surgery
Trauma
Peripheral vascular disease
Skin popping

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What is type I necrotising fasciitis?

Mixed aerobic and anaerobic infection

What are typical organisms causing necrotising fasciitis?

Streptococci
Staphylococci
Enterococci
Gram negative bacilli
Clostridium

What is type II necrotising fasciitis?

Monomicrobial

What is the most common causative organism of type II necrotising fasciitis?

Strep pyogenes

What are features of necrotising fasciitis?

Rapid onset Sequential development of erythema, extensive oedema, severe unremitting pain Haemorrhagic bullae, skin necrosis Anaesthesia at site is highly suggestive Systemic features - fever, hypotension, tachycardia, delirium, multiorgan failure

How is necrotising fasciitis treated?

Surgical review mandatory | Broad spectrum antibiotics - flucloxacillin, gentamicin, clindamycin

What is pyomyositis?

Purulent infection deep within striated muscle - abscess

What are common sites for pyomyositis?

``` Thigh Calf Arms Gluteal region Chest wall Psoas muscle ```

What are predisposing factors for pyomyositis?

``` Diabetes mellitus HIV/immunocompromised IV drug use Rheumatological disease Malignancy Liver cirrhosis ```

What is the most common causative organism of pyomyositis?

Staph aureus

What investigation is done for pyomyositis?

CT/MRI

How is pyomyositis treated?

Drainage with antibiotic cover dependent on gram stain and culture results

What are the most common sites of septic bursitis?

Patella | Olecranon

What causes septic bursitis?

Adjacent skin infection

What are predisposing factors for septic bursitis?

``` Rheumatoid arthritis Alcoholism Diabetes mellitus IV drug abuse Immunosuppresion Renal insufficiency ```

What are features of septic bursitis?

Peribursal cellulitis, swelling, warmth Fever Pain on movement

How is septic bursitis diagnosed?

Aspiration of fluid

What is the most common causative organism of septic bursitis?

Staph aureus

What is infectious tenosynovitis?

Infection of synovial sheets around tendons

What tendons are most commonly involved in infectious tenosynovitis?

Flexor muscle-associated tendons | Tendon sheets of the hand

What are the most common causative organisms of infectious tenosynovitis?

Staph aureus | Streptococci

How does infectious tenosynovitis present?

Erythematous fusiform swelling of finger Held in semiflexed position Tenderness over length of tendon sheet Pain with extension of finger

How is infectious tenosynovitis treated?

Empiric antibiotics | Hand surgeon review

What is diagnostic criteria for staph aureus toxic shock syndrome?

Fever Hypotension Diffuse macular rash Three of the following involved - liver, blood, renal, GI, CNS, muscular Isolation of staph aureus from normally sterile sites Production of TSST1 by isolate Development of antibody to toxin during convalescence

How is streptococcal toxic shock syndrome treated?

``` Remove offending agent IV fluids Inotropes Antibiotics IV immunoglobulins ```

What is staphylococcal scalded skin syndrome?

Infection with particular strain of staph aureus producing exfoliative toxin A or B Characterised by widespread bullae and skin exfoliation

How is staphylococcal scalded skin syndrome treated?

IV fluids and antimicrobials

What are risk factors for IV catheter associated infection?

Continuous infusion >24 hours Cannula in situ >72 hours Cannula in lower limb Patients with neuro problems

What is the most common causative organism of IV catheter associated infection?

Staph aureus

How is IV catheter associated infection prevented?

Do not leave unused canula Do not insert canula unless using them Change canula ever 72 hours Use aseptic technique when inserting cannula

What are patient associated risk factors for surgical site infections?

``` Diabetes Smoking Obesity Malnutrition Concurrent steroid use Colonisation with staph aureus ```

What are procedural risk factors for surgical site infection?

``` Shaving of the site the night prior to procedure Improper preoperative skin preparation Improper antimicrobial prophylaxis Break in sterile technique Inadequate theatre ventilation Perioperative hypoxia ```

How is surgical site infection diagnosed?

Pus/infected tissue culture | Avoid superficial swab - aim for deep structures