SSTIs and PUO

Question 1

How does the treatment of cellulitis and infections of the skin above differ from necrotising fasciitis and the layers below?

Answer 1

Cellulitis and above → just ABs

Nec Fasc and below → ABs + surgical debridement (+ usually no empirical ABs, need to confirm organism with surgical sample)

Question 2

What are the classical features of cellulitis and how does it differ from erysipelas?

Answer 2

Both usually hot, red, tender
Cellulitis involved SQ → more diffuse margin compared to erysipelas

Question 3

What are the classical features of impetigo?

Answer 3

In children, perioral, starts as vesicle → ruptures releasing yellowish, thick, wet crust

Question 4

What is the main causative organism for cellulitis?

Answer 4

1) Staph Aureus
2) ß-hemolytic strep (esp. GAS)

Question 5

What is the main causative organism for impetigo?

Answer 5

1) Staph Aureus
2) ß-hemolytic strep (esp. GAS)

Question 6

What is the main causative organism for folliculitis?

Answer 6

1) Staph Aureus
2) ß-hemolytic strep (esp. GAS)
3) Pseudomonas aeruginosa (hot tub folliculitis)

Question 7

What is the main causative organism for furuncles?

Answer 7

1) Staph Aureus
2) ß-hemolytic strep (esp. GAS)

Question 8

What is the main causative organism for carbuncles?

Answer 8

1) Staph Aureus
2) ß-hemolytic strep (esp. GAS)

Question 9

What is the main causative organism for erysipelas?

Answer 9

1) Group A strep

Question 10

What are the classical features of lymphangitis?

Answer 10

Red tracking linear streaks towards regional lymph nodes, which are enlarged and tender
- may present with swollen limb

Question 11

What is the main causative organism for lymphangitis?

Answer 11

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)

Question 12

What are the classical features of intertrigo?

Answer 12

chronic, subtle onset of pruritus, burning, tingling, and pain in the skin folds and flexural surfaces
- esp in high BMI and DM px

Question 13

What are 2 common causative organisms of intertrigo?

Answer 13

1) Staph aureus
2) Candida
3) Coliforms

Question 14

How do type 1 and 2 necrotising fasciitis differ?

Answer 14

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

Question 15

What are 2 common causative organisms of gas gangrene (myonecrosis)?

Answer 15

1) Clostridium perfringens (necrotic tissue)
2) Spontaneous/hematogenous (group A strep)

Immunocompromised/w risk factors:
3) Clostridia
4) Staph aureus
5) Vibro vulnificus

Question 16

What must be done before collecting a swab from a diabetic foot ulcer?

Answer 16

Cleanse and debride superficial layer to remove other organisms

Question 17

What is needed to guide antibiotic therapy in a chronic wound/ diabetic foot ulcer?

Answer 17

Deep tissue culture

Question 18

How do the typical causative organism for diabetic foot ulcers differ for (i) a new onset infection (ii) chronic wounds?

Answer 18

i) Staph aureus/Group A Strep

ii) Gram neg/mixture of gram neg and pos

Question 19

What are 5 microbiological testing options for SSTIs?

Answer 19

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

Question 20

How does hematogenous osteomyelitis differ in children and adults?

Answer 20

Children: long bones (tibia and femur)
Adults: adjacent vertebral bodies

Question 21

What is the main causative organisms of hematogenous osteomyelitis?

Answer 21

1) Staph aureus

If <1y/o
2) Coag neg staph
3) GBS
4) E coli

Question 22

What are 2 main causative organisms of osteomyelitis by contiguous spread?

Answer 22

1) Staph aureus
2) GAS
3) CONS (prosthesis)

Question 23

What are 2 ways to diagnose osteomyelitis?

Answer 23

1) MRI
2) Tissue culture (must take in OT)
3) CT guided biopsy

Question 24

Should empirical antibiotics be given for a px with suspected osteomyelitis?

Answer 24

NO
- decreases chances of growing causative organism

Question 25

How long is the typical antibiotic course for osteomyelitis?

Answer 25

at least 6 weeks

Question 26

What are 2 main causative organisms of prosthetic joint infections?

Answer 26

1) Coagulative negative staph 2) Staph aureus

Question 27

Should empirical antibiotics be given for a px with suspected prosthetic joint infection?

Answer 27

No - decreases chances of growing causative organism

Question 28

How is a prosthetic joint infection diagnosed?

Answer 28

NOT gram stain - need to culture → intraoperative tissue/pis

Question 29

What are 2 ways to treat prosthetic joint infections?

Answer 29

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

Question 30

How are antibiotics typically administered for osteomyelitis/prosthetic joint infections?

Answer 30

IV - oral only if excellent OF

Question 31

True or false: acute monoarticular arthritis is septic arthritis until otherwise proven

Answer 31

True

Question 32

What is the main causative organism of septic arthritis?

Answer 32

Staph aureus

Question 33

How is septic arthritis typically diagnosed?

Answer 33

Joint aspiration: 1) High WCC (w predominance of neutrophils) 2) Gram stain 3) Culture

Question 34

How is septic arthritis treated?

Answer 34

1) Joint washout 2) 2-6 weeks of ABs

Question 35

What is the clinical definition of PUO?

Answer 35

1) illness >3wks 2) >38.3°C on several occasions 3) No diagnosis after 1 wk of routine workup in hospital

Question 36

True or false: A documented pattern of fever using a electronic thermometer taken at 7am daily is enough to narrow a diagnosis for PUO.

Answer 36

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

Question 37

What are the 3 main causes of PUO?

Answer 37

1) Infection 2) Neoplasm 3) Autoimmune disease Others: 4) Drugs 5) Factitious fever 6) Pulmonary emboli 7) Familial Mediterranean fever

Question 38

Should a px with PUO be given broad-spectrum empirical antibiotics to reduce morbidity?

Answer 38

No. - discontinue ABs for 1 wk prior to Ix if safe

Question 39

What are 3 infective causes of PUO?

Answer 39

1) Abscess 2) Endocarditis 3) Osteomyelitis 4) Biliary infection 5) Pyelonephritis (subacute) 6) TB 7) Brucellosis 8) Viral infection/cryptococcus/histoplasmosis/toxoplasmosis/malaria

Question 40

What are 2 neoplastic causes of PUO?

Answer 40

1) Lymphoma (esp. hodgkin's) 2) Leukemia 3) Primary hepatoma (metastatic rarely pyretic) 4) Renal cell 5) Atrial myxoma

Question 41

What are 3 autoimmune causes of PUO?

Answer 41

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)

Question 42

Should anti-pyretics be given to px with PUO?

Answer 42

Yes only once fever episodes are documented