Skin and Soft Tissue Infections Flashcards
What is the cause of impetigo?
Staph aureus
What does impetigo look like?
Multiple vesicular lesions on an erythematous base
Golden crust highly suggestive
What are the predisposing factors for impetigo?
Skin abrasions Minor trauma Burns Poor hygiene Insect bites Chickenpox Eczema Atopic dermatitis
What is the treatment for impetigo?
Small areas topical antibiotics
Larger areas oral antibiotics
What is erysipelas?
Infection of the upper dermis
What does erysipelas look like?
Distinct elevated borders
Painful red area
What is the cause of erysipelas?
Strep pyogenes
What are the clinical signs of erysipelas?
Associated fever
Regional lymphadenopathy and lymphangitis
Where is erysipelas likely to occur on the body?
Lower limbs
Face
What is cellulitis?
Diffuse skin infection involving deep dermis and subcutaneous fat
What does cellulitis look like?
Spreading erythematous area with no distinct borders
What is the cause of cellulitis?
Strep pyogenes
Staph aureus
What are the predisposing factors for cellulitis?
Diabetes
Tinea pedis
Lymphoedema
What is the treatment for cellulitis and erysipelas?
Combination of anti-staphylococcal and anti-streptococcal antibiotics
What is folliculitis?
Circumscribed, pustular infection of hair follicle
Where is folliculitis typically found?
Head
Back
Buttocks
Extremities
What is the cause of folliculitis?
Staph aureus
What is furunculosis?
Single hair follicle associated inflammatory nodule, extending into the dermis and subcutaneous tissue
What areas are commonly affected by furunculosis?
Moist, hairy, friction-prone areas (face, axilla, neck, buttocks)
What is the cause of furunculosis?
Staph aureus
What are the risk factors for furunculosis?
Obesity Diabetes Atopic dermatitis Chronic kidney disease Corticoidsteroid use
What is a carbuncle?
Occurs when infection extends to involve multiple furuncles
Where are carbuncles typically found?
Back of neck
Posterior trunk or thigh
What is the treatment for folliculitis?
No treatment of topical antibiotics
What is the treatment for furunculosis?
No treatment of topical antibiotics
What is the treatment for carbuncles?
Hospital admission, surgery, IV antibiotics
What are the predisposing factors for necrotising fasciitis?
Diabetes Surgery Trauma Peripheral vascular disease Skin popping
What is type 1 necrotising fasciitis?
Mixed aerobic and anaerobic infection
What organisms could be the cause of necrotising fasciitis?
Streptococci Staphylococci Enterococci Gram negative bacilli Clostridium
What is type 2 necrotising fasciitis?
Monomicrobial
What is the organism which causes type 2 necrotising fasciitis?
Strep pyogenes
What are the symptoms of necrotising fasciitis?
Erythema Extensive oedema Severe, unremitting pain Haemorrhage bullae Skin necrosis Crepitus
What are the systemic features of necrotising fasciitis?
Fever Hypotension Tachycardia Delirium Multiorgan failure
What is the treatment for necrotising fasciitis?
Surgical review mandatory
Broad spectrum antibiotics (flucloxacillin, gentamicin, clindamycin)
What is pyomyositis?
Purulent infection deep within striated muscle, often manifesting as an abscess
What are the common sites of pyomyositis?
Thigh Calf Arms Gluteal region Chest wall Psoas muscle
What are the predisposing factors for pyomysitis?
Diabetes HIV/immunocompromised IV drug use Rheumatological disease Malignancy Liver cirrhosis
What is the presentation of pyomyositis?
Fever
Pain and woody induration of affected muscle
What is the organism that causes pyomyositis?
Staph aureus
Gram positives/negaitves, TB, fungi
What is the treatment for pyomyositis?
Drainage with antibiotic cover depending on gram stain and culture results
What is septic bursitis?
Infection of bursar found between bony prominences or tendons
What are the predisposing factors for septic bursitis?
Rheumatoid arthritis Diabetes Alcoholism IV drug use Immunosuppression Renal insufficiency
What are the features of septic bursitis?
Peribursal cellulitis
Swelling and warmth
Fever
Pain on movement
What is the organism that causes septic bursitis?
Staph aureus
Rarer (gram negatives, mycobacteria, brucella)
What is infectious tenosynovitis?
Infection of the synovial sheaths that surround tendons
What areas are typically affected by infectious tenosynovitis?
Flexor muscle associated tendons
Tendon sheaths of the hand
What is the organism that causes infectious tenosynovitis?
Staph aureus
Streptococci
What is the presentation of infectious tenosynovitis?
Erythematous fusiform swelling of finger
Held in semiflexed position
Tenderness over the length of the tendon sheath and pain with extension of finger
What is the treatment for infectious tenosynovitis?
Empiric antibiotics
Hand surgeon review
What is the organism that causes toxin-mediated syndromes?
Staph aureus
Strep pyogenes
What is a toxin-mediated syndrome?
Superantigens bypass APC and T cell activation and attach directly to T cell receptors causing a massive burst in cytokine release
What is the diagnostic criteria for staphylococcal toxic shock syndrome?
Fever
Hypotension
Diffuse macular rash
3 of the flooring involved (liver, blood, renal, gastrointestinal, CNS, muscular)
Isolation of staph aureus from mucosal or normally sterile sites
Production of TSST1 by isolate
Development of antibody to toxin during convalescence
What is the treatment for streptococcal toxic shock syndrome?
Urgent surgical debridement of the infected tissues Remove offending agent (tampon) IV fluids Inotropes Antibiotics IV immunoglobulins
What is staphylococcal scalded skin syndrome?
Infection due to a particular strain of staph aureus producing the exfoliative toxin A or B
How is staphylococcal scalded skin syndrome characterised?
Widespread bullae
Skin exfoliation
What is the treatment for staphylococcal scalded skin syndrome?
IV fluids and antimicrobials
What is Panton-Valentine leucocidin toxin?
Gamma haemolysin which can be transferred from one strain of staph aureus to another including MRSA
What is the presentation of Panton-Valentine leucocidin toxin?
Recurrent boils which are difficult to treat
What is the treatment for Panton-Valentine leucocidin toxin?
Antibiotics that reduce toxin production
What are the risk factors for intravenous-catheter associated infections?
Continuous infusions >24hrs
Cannula in situ >72hours
Cannula in lower limb
Patients with neurological/ neurosurgical problems
What is the treatment for intravenous-catheter associated infections?
Remove cannula
Express any pus from the thrombophlebitis
Antibiotics 14 days
Echocardiogram
What are the preventative measures for intravenous-catheter associated infections?
Don't leave unused cannula Don't insert cannula unless using it Change cannula every 72 hours Monitor for thrombophlebitis Use aseptic technique when inserting cannulae
What is a class 1 surgical site infection?
Clean wound (respiratory, alimentary, genital or infected urinary systems not entered)
What is a class 2 surgical site infection?
Clean-contaminated wound (tracts entered but no unusual contamination)
What is a class 3 surgical site infection?
Contaminated wound (open, fresh, accidental wounds or gross spillage from the GI tract)
What is a class 4 surgical site infection?
Infected wound (existing clinical infection, infection present before operation)
What are the causes of surgical site infections?
Staph aureus (incl MRSA and MSSA) Coagulase negative staphylococci Enterococcus Escherichia coli Pseudomonas aeroginosa Enterobacter Streptococci
What are the patient associated risk factors for surgical site infections?
Diabetes Smoking Obesity Malnutrition Concurrent steroid use Colonisation with staph aureus
What are the procedural risk factors for surgical site infections?
Shaving of site the night prior to procedure Improper preoperative skin preparation Improper antimicrobial prophylaxis Break in sterile technique Inadequate theatre ventilation Preoperative hypoxia
