Skin and Soft Tissue Infections

Question 1

Impetigo

Answer 1

Multiple vesicular lesions - golden crust

Staph aureus - most common (less common strep pyogenes)

Common in age 2-5
Highly infectious
Common in exposed extremities
Predisposing factors - break in skin: burn, trauma, abrasion, bite, eczema, poor hygiene

Treatment: small area: topical antibiotics - MUPURCIN (bactroban)
Large area: topical and oral antibiotics

Question 2

Erysipelas

Answer 2

Upper dermis infection
Painful red area - most common in face and limbs
Associated fever, regional lymphadenopathy
Tends to occur in areas of pre-existing lymphoedema, venous stasis, obesity, paraparesis, DM
High reocurrance rate - 30% in 3 years

Strep Pyogenes

Treat - oral antibiotics, if severe IV antibiotics and rest

Question 3

Cellulitis

Answer 3

Deep dermis and subcutaneous fat and epidermis
SPREADING erythematous area with NO distinct borders.

Fever common
regional lymphadenopathy and lympahangitis
Diabetes, tinea pedis, lymphoedema

Most common: staph aureus and strep pyogenes

Treatment: oral antibiotics, if severe IV antibiotics and rest

Question 4

Name 3 hair-associated infections

Answer 4

Folliculitis
Furunculosis
Carbuncle

Question 5

Folliculitis

Answer 5

Superficial and deep
circumscribed, pustular infection of a hair follicle up to 5mm in diameter. Typically found on head, back, buttocks and extremities

most commonly caused by staph aureus

Treatment: topical Flucloxacilin

Question 6

Furunculosis

Answer 6

Inflammation of a single hair follicle that extends deep into dermis and sub-cutaneous tissue

Affects moist hairy areas

Staph aureus

Flucloxacilin or no treatment - oral antibiotics if persisting

Question 7

Carbuncle

Answer 7

Multiple furuncles.

Pus-filled. may drain spontaneously. Constitutional symptoms common.

Treat - often admitted, surgery and IV antibiotics

Question 8

Necrotising Fasciitis

Answer 8

Emergency. Rapid onset.

Erythema - oedema - severe unremitting pain.

presents as haemorrhagic bullae, skin necrosis and crepitus. Often have anaesthesia of the location.

Systemic features: fever, hypotension, tachycardic, delirium, multiorgan failure.

Type 1 - mixed aerobic and anaerobic
Type 2 - single pathogen - usually strep pyogenes

Question 9

Pyomysitis

Answer 9

Purulent infection deep within striated muscles- can result in muscle abscess. multiple sites can be affected. Constitutional symptoms common.

Predisposing factors: diabetes, HIV/immunocompromised, IVDU, malignancies, liver cirrhosis.

Investigations: CT/MRI

Staph aureus.

Treatment: drainage with antibiotic cover - Surgery may be needed.

Question 10

Septic Bursitis

Answer 10

Commonly effected: patellar/olecranon bursae. Constitutional symptoms common.

Staph aureus

Diagnosis based on aspiration of fluid- differential = septic arthritis

Question 11

Infectious Tenosynovitis

Answer 11

Most commonly effects flexor synovial sheats around tendons in hands.

Presents with erythematous swelling and finger held in semi-flexed position.

Staph aureus and strep pyogenes

Treat: empiric antibiotics and refer for surgery

Question 12

Toxin-mediated syndromes

Answer 12

Gram positive - Exotoxins - superantigens -

usually staph aureus or strep pyrogenes

Question 13

Toxic Shock Syndrome

Answer 13

Staphylococcal TSS: fever, hypotension, diffuse macular rash. Three end organ involvement. TSST1 production. fatality rate: 5%.

Streptococcal TSS: usually always presents with deep seated infections such as erysipelas/nec fas. fatality rate: 50%. Requires surgery to remove infected tissues.

TREATMENT: remove offending agent, IV fluids, inotropes, antibiotics, IV immunoglobulins

Question 14

Staphylococcal scalded skin syndrome

Answer 14

Infection due to a particular strain of staph a producing exfoliative toxin A or B. More common in children.

TREATMENT: IV fluids and antimicrobials

Question 15

IV-catheter associated infection

Answer 15

Risk factors: continuous infusion >24 hours, cannula in situ >72 hours, cannula in lower limb, patients with neurological/neurosurgical problems.

Question 16

IV-catheter associated infection

Answer 16

Risk factors: continuous infusion >24 hours, cannula in situ >72 hours, cannula in lower limb, patients with neurological/neurosurgical problems.

Treatment: remove cannula, express pus , antibiotics for 14 days, echocardiogram. prevention is more important.

Question 17

Classifications of surgical wounds

Answer 17

Class I: clean wound
Class II: clean-contaminated
Class III: contaminated wound
Class IV: infected wound

Question 18

What infections need urgent attention? (5)

Answer 18

Nec fas
Pyomyositis
TSS
PVL infections
Venflon associated infections