Skin and soft tissue infections Flashcards
What is impetigo?
Superficial skin infection - multiple vesicular lesions on an erythematous base
What is the peak age for impetigo?
2-5 years age
What are predisposing factors for impetigo?
Skin abrasions Minor trauma Burns Poor hygiene Insect bites Chickenpox Eczema Atopic dermatitis
How is impetigo treated?
Topical antibiotics
What is erysipelas?
Infection of the upper dermis - painful red area, associated fever, regional lymphadenopathy, elevated borders
What is the most common causative organism for erysipelas?
Strep pyogenes
What is cellulitis?
Diffuse skin infection involving deep dermis and subcutaneous fat
What are features of cellulitis?
Presents as spreading erythematous area with no distinct borders
Fever
Regional lymphadenopathy
Possible source of bacteraemia
What are common causative organisms of cellulitis?
Strep pyogenes
Staph aureus
What are predisposing factors for cellulitis?
Diabetes mellitus
Tinea pedis
Lymphoedema
How is cellulitis treated?
Combination of anti-staphylococcal and anti-streptococcal antibiotics
What are hair-associated infections?
Folliculitis
Furunculosis
Carbuncles
What is folliculitis?
Circumscribed pustular infection of a hair follicle
Where is folliculitis typically found?
Head
Back
Buttocks
Extremities
What is the most common causative organism for folliculitis?
Staph aureus
What is furunculosis?
Single hair follicle-associated inflammatory nodule extending into dermis and subcutaneous tissue
What are common affected areas of furunculosis?
Moist, hairy, friction prone areas - face, axilla, neck, buttocks
What are risk factors for furunculosis?
Obesity Diabetes mellitus Atopic dermatitis Chronic kidney disease Corticosteroid use
What is carbuncle?
When infection extends to multiple furuncles
Where are carbuncles located?
Back of neck
Posterior trunk
Thigh
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
What are predisposing factors for necrotising fasciitis?
Diabetes mellitus Surgery Trauma Peripheral vascular disease Skin popping
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
