Skin and Soft Tissue Infections Flashcards
What are the features of impetigo?
- Superficial skin infection
- Highly infectious
- Multiple vesicular lesions on an erythematous base
- Golden crust
- Usually on exposed parts of the body
Which organisms can cause impetigo?
- Staph aureus (common)
- Strep pyogenes (less common)
What are the predisposing factors for impetigo?
- Skin abrasions
- Minor trauma
- Burns
- Poor hygiene
- Insect bites
- Chickenpox
- Eczema
- Atopic dermatitis
How can impetigo be treated?
- Small areas: topical antibiotics
- Large areas topical treatment and oral antibiotics
What are the features of erysipelas?
- Infection of the upper dermis
- Painful, red area
- Fever, lymphadenopathy and lymphangitis
- Mostly affects the lower limbs
- Distinct elevated borders
- Tends to occur in areas of pre-existing lymphoedema, venous stasis, obesity, paraparesis and diabetes
Which organism commonly causes erysipelas?
Strep pyogenes
What are the features of cellulitis?
- Skin infection involvin deep dermis and subcut fat
- Spreading erythematous area
- Fever
- Regional lymphadenopathy and lymphangitis
- Predisposing factors: diabetes, tinea pedis and lymphoedema
Which organisms commonly cause cellulitis?
- Strep pyogenes
- Staph aureus
- Gram negatives in diabetics and febrile neutropaenics
How can erysipelas and cellulitis be treated?
- Combination of anti-staph and anti-strep antibiotics
- Extensive disease: IV antibiotics and rest
What is folliculitis and how does it present?
- Circumscribed, pustular infection of a hair follicle
- Small red papules
- Central area may rupture and drain
- Head, back, buttocks and extremities
Which organism commonly causes folliculitis?
Staph aureus
What are the features of furunculosis?
- Boils
- Single hair follicle associated inflamm. nodule
- Extends into dermis and subcut tissue
- Affects moist, hairy, friction prone areas
Which organism commonly causes furunculosis?
Staph aureus
What are the risk factors for furunculosis?
- Obesity
- Diabetes
- Atopic dermatitis
- Chronic kidney disease
- Corticosteroid use
What is a carbuncle and what are the features of them?
- Infection which has extended to involve multiple furuncles
- Multiseptated abscesses
- Purulent material
How are hair-associated infections treated?
- Folliculitis: no treatment
- Furunculosis: if not improving then oral antibiotics
- Carbuncles: may require admission, surgery and IV antibiotics
What are the predisposing conditions for necrotising fasciitis?
- Diabetes
- Surgery
- Trauma
- Peripheral vascular disease
- Skin popping
What is type 1 necrotising fasciitis and which organisms typically cause it?
- Mixed aerobic and anaetobiv infection (diabetic foot infection and Fournier’s gangrene)
- Strep, staph, enterococci, gram negative bacilli and clostridium
What is type 2 necrotising fasciitis and which organism typically causes it?
- Monomicrobial
- Strep pyogenes
What are the features of necrotising fasciitis?
- Rapid onset
- Erythema, oedema and severe pain
- Haemorrhagic bullae, skin necrosis and crepitus
- Fever, hypotension, tachycardia, delirium and multiorgan failure
- Anaesthesia at site of infection
How is necrotising fasciitis managed?
- Surgical review
- Broad spectrum antibiotics: fluclox, gentamicin and clindamycin
What is pyomyositis?
Purulent infection deep within striated muscle often as an abscess
What are the common sites for pyomyositis?
- Thigh
- Calf
- Arms
- Gluteal region
- Chest wall
- Psoas muscle
How does pyomyositis present?
- Fever
- Pain
- Woody induration of affected muscle
- Can lead to septic shock and death
What are the predisposing factors for pyomyositis?
- Diabetes
- HIV/ immunocompromised
- IVDA
- Rheumatological diseases
- Malignancy
- Liver cirrhosis
Which organisms can cause pyomyositis?
- Staph aureus
- Gram positives/negatives, TB and fungi
How is pyomyositis investigated and how is it treated?
- CT/MRI, gram stain and culture
- Specific antibiotics
What are the predisposing factors for septic bursitis?
- Rheumatoid arthritis
- Alcoholism
- Diabetes mellitus
- IVDA
- Immunosuppression
- Renal insufficiency
What are the features of septic bursitis?
- Peribursal cellulitis
- Swelling
- Warmth
- Fever
- Pain on movement
How is septic bursitis diagnosed and which organisms are involved?
- Aspiration
- Most common is staph aureus
- Gram negative, mycobacteria and brucella
Which organisms cause infectious tenosynovitis?
- Staph aureus and strep
- Chronic infections due to mycobacteria and fungi
- Disseminated gonococcal infection
How does infectious tenosynovitis present?
- Erythematous fusiform swellling of the finger
- Finger held in semiflexed position
- Tenderness over the length of the tendon sheet and pain with extension of the finger
How is infectious tenosynovitis treated?
- Empiric antibiotics
- Hand surgeon review ASAP
Which organisms cause toxin mediated syndromes?
- Staph aureus
- Strep pyogenes
What are the diagnostic criteria for staph TSS?
- Fever
- Hypotension
- Diffuse macular rash
- Three of the following organs involved: liver, blood, renal, GI, CNS and muscular
- Isolation of staph aureus from mucosal or normally sterile sites
- Production of TSSTq
- Development of antibody to toxin
What additional treatment does strep TSS need?
Urgent surgical debridement of the infected tissues
How is TSS treated?
- Remove offending agent
- IV fluids
- Inotropes
- Antibiotics
- IV immunoglobulins
What are the features of staph scalded skin syndrome?
- Infection by staph
- Widespread bullae and skin exfoliation
- Usually in children
How is scalded skin syndrome treated?
- IV fluids
- Antimicrobials
What does the panton valentine leucocidin toxin cause and how is it treated?
- SSTI and haemorrhagic pneumonia
- Recurrent boils that are difficult to treat
- Treated with antibiotics
Which organism most commonly causes intravenous catheter associated infections?
Staph aureus (MSSA and MRSA)
How are intravenous catheter associated infections diagnosed and how are they treated?
- Clinically or positive blood cultures
- Remove cannular
- Express any pus
- Antibiotics for 14 days
- ECHO
How can IV catheter infections be prevented?
- Remove unsued cannulas
- Only insert cannulas when in use
- Change cannulae every 72hrs
- Monitor for thrombophlebitis
- Aseptic technique for insertion
How are surgical wounds classified?
- Class 1: clean wound (resp, GI, genital and urinary systems not entered)
- Class 2: clean contaminated wound (above tracts entered but no unusual contamination
- Class 3: contaminated wound
- Class 4: infected wound
Which organisms cause surgical site infections?
- Staph aureus
- Coagulase negative staph
- Enterococci
- E coli
- Pseudomonas
- Enterobacter
- Strep
- Fungi
- Anaerobes
What are the risk factors for surgical site infections?
- Diabetes
- Smoking
- Obesity
- Malnutrition
- Concurrent steroid use
- Colonisation with staph aureus
- Shaving of site night prior
- Improper skin prep
- Improper antimicrobial prophylaxis
- Break in sterile technique
- Inadequate theatre ventilation
- Perioperative hypoxia
How can surgical site infections be diagnosed and how are they treated?
- Pus/infected tissue for cultures (deep swabs)
- Antibiotics to target likely organisms
