SSTIs and PUO Flashcards
How does the treatment of cellulitis and infections of the skin above differ from necrotising fasciitis and the layers below?
Cellulitis and above → just ABs
Nec Fasc and below → ABs + surgical debridement (+ usually no empirical ABs, need to confirm organism with surgical sample)
What are the classical features of cellulitis and how does it differ from erysipelas?
Both usually hot, red, tender
Cellulitis involved SQ → more diffuse margin compared to erysipelas
What are the classical features of impetigo?
In children, perioral, starts as vesicle → ruptures releasing yellowish, thick, wet crust
What is the main causative organism for cellulitis?
1) Staph Aureus
2) ß-hemolytic strep (esp. GAS)
What is the main causative organism for impetigo?
1) Staph Aureus
2) ß-hemolytic strep (esp. GAS)
What is the main causative organism for folliculitis?
1) Staph Aureus
2) ß-hemolytic strep (esp. GAS)
3) Pseudomonas aeruginosa (hot tub folliculitis)
What is the main causative organism for furuncles?
1) Staph Aureus
2) ß-hemolytic strep (esp. GAS)
What is the main causative organism for carbuncles?
1) Staph Aureus
2) ß-hemolytic strep (esp. GAS)
What is the main causative organism for erysipelas?
1) Group A strep
What are the classical features of lymphangitis?
Red tracking linear streaks towards regional lymph nodes, which are enlarged and tender
- may present with swollen limb
What is the main causative organism for lymphangitis?
1) Group A strep (acute)
2) Pasteurella multocida (cat scratch, acute)
3) Filariasis
4) Mycobacterium marinum (swimming pool granuloma, chronic)
5) Sporothrix schenckii (rose thorn, chronic)
What are the classical features of intertrigo?
chronic, subtle onset of pruritus, burning, tingling, and pain in the skin folds and flexural surfaces
- esp in high BMI and DM px
What are 2 common causative organisms of intertrigo?
1) Staph aureus
2) Candida
3) Coliforms
How do type 1 and 2 necrotising fasciitis differ?
1) Area:
1: mainly perineal, genital, perianal
2: mainly lower limbs
2) Pain
2: classically out of proportion with skin appearance
3) Causative organisms
1: polymicrobial
2: group A strep, Staph aureus
What are 2 common causative organisms of gas gangrene (myonecrosis)?
1) Clostridium perfringens (necrotic tissue)
2) Spontaneous/hematogenous (group A strep)
Immunocompromised/w risk factors:
3) Clostridia
4) Staph aureus
5) Vibro vulnificus
What must be done before collecting a swab from a diabetic foot ulcer?
Cleanse and debride superficial layer to remove other organisms
What is needed to guide antibiotic therapy in a chronic wound/ diabetic foot ulcer?
Deep tissue culture
How do the typical causative organism for diabetic foot ulcers differ for (i) a new onset infection (ii) chronic wounds?
i) Staph aureus/Group A Strep
ii) Gram neg/mixture of gram neg and pos
What are 5 microbiological testing options for SSTIs?
1) WET wound swab (dry=skin flora)
2) Skin scrapings
- scabies, skin fungal infection
3) Pus swab
4) Pus aspirate
5) Tissue culture
- myositis/nec fasc
6) Deep tissue culture/biopsy
- diabetic foot uclers
7) Blood culture
- septic/pyrexial px
How does hematogenous osteomyelitis differ in children and adults?
Children: long bones (tibia and femur)
Adults: adjacent vertebral bodies
What is the main causative organisms of hematogenous osteomyelitis?
1) Staph aureus
If <1y/o
2) Coag neg staph
3) GBS
4) E coli
What are 2 main causative organisms of osteomyelitis by contiguous spread?
1) Staph aureus
2) GAS
3) CONS (prosthesis)
What are 2 ways to diagnose osteomyelitis?
1) MRI
2) Tissue culture (must take in OT)
3) CT guided biopsy
Should empirical antibiotics be given for a px with suspected osteomyelitis?
NO
- decreases chances of growing causative organism
How long is the typical antibiotic course for osteomyelitis?
at least 6 weeks
What are 2 main causative organisms of prosthetic joint infections?
1) Coagulative negative staph
2) Staph aureus
Should empirical antibiotics be given for a px with suspected prosthetic joint infection?
No
- decreases chances of growing causative organism
How is a prosthetic joint infection diagnosed?
NOT gram stain
- need to culture → intraoperative tissue/pis
What are 2 ways to treat prosthetic joint infections?
1) 1 stage exchange arthroplasty
- change new prosthesis with same operation with antibiotic loaded cement
2) 2 stage approach
i) remove infected prosthesis
ii) install antibiotic loaded cement + spacer to stabilise bone
iii) insert new prosthesis after prolonged course of antibiotics
How are antibiotics typically administered for osteomyelitis/prosthetic joint infections?
IV
- oral only if excellent OF
True or false: acute monoarticular arthritis is septic arthritis until otherwise proven
True
What is the main causative organism of septic arthritis?
Staph aureus
How is septic arthritis typically diagnosed?
Joint aspiration:
1) High WCC (w predominance of neutrophils)
2) Gram stain
3) Culture
How is septic arthritis treated?
1) Joint washout
2) 2-6 weeks of ABs
What is the clinical definition of PUO?
1) illness >3wks
2) >38.3°C on several occasions
3) No diagnosis after 1 wk of routine workup in hospital
True or false: A documented pattern of fever using a electronic thermometer taken at 7am daily is enough to narrow a diagnosis for PUO.
False.
- Need to take w electronic thermometer
- need to measure BOTH 6am and 6pm to exclude exaggerated circadian rhythm
- pattern of fever insufficient to diagnose
What are the 3 main causes of PUO?
1) Infection
2) Neoplasm
3) Autoimmune disease
Others:
4) Drugs
5) Factitious fever
6) Pulmonary emboli
7) Familial Mediterranean fever
Should a px with PUO be given broad-spectrum empirical antibiotics to reduce morbidity?
No.
- discontinue ABs for 1 wk prior to Ix if safe
What are 3 infective causes of PUO?
1) Abscess
2) Endocarditis
3) Osteomyelitis
4) Biliary infection
5) Pyelonephritis (subacute)
6) TB
7) Brucellosis
8) Viral infection/cryptococcus/histoplasmosis/toxoplasmosis/malaria
What are 2 neoplastic causes of PUO?
1) Lymphoma (esp. hodgkin’s)
2) Leukemia
3) Primary hepatoma (metastatic rarely pyretic)
4) Renal cell
5) Atrial myxoma
What are 3 autoimmune causes of PUO?
1) SLE
2) Still’s disease (adult onset juvenile RA)
3) Polymyalgia rheumatica (elderly w temporal arteritis)
4) Polyarteritis nodosa
5) Mixed connective tissue disease
6) Subacute thyroiditis
7) Kikuchi’s disease (young asian F with generalised lymphadenopathy)
Should anti-pyretics be given to px with PUO?
Yes only once fever episodes are documented
