Skin/Soft Tissue Infections

Question 1

Define cellulitis

Answer 1

Inflammation of the skin and subcutaneous tissue

Question 2

What causes cellulitis?

Answer 2

Infection

Question 3

Differentiate erysipelas from cellulitis

Answer 3

Erysipelas: upper dermis and superficial lymphatics

Cellulitis: deeper dermis and subcutaneous fat

Question 4

List some predisposing factors for cellulitis

Answer 4

Break in skin barrier
Edema/water retention
Skin conditions
Immunosuppression
Co-morbidities
Procedures
other infections...

Question 5

What are the most common bugs that cause cellulitis?

Answer 5

Strep and Staph

Question 6

How do you get eikenella corrodens?

Answer 6

Human bite

Question 7

How do you get pasteurella multocida?

Answer 7

Cat bites

Question 8

How do you get capnocytophaga canimorsus?

Answer 8

Dog bites

Question 9

Which pathogen is most associated with purulent cellulitis?

Answer 9

CA-MRSA

Question 10

WHich species tend to cause non-purulent cellulitis?

Answer 10

MSSA Staph and Strep

Question 11

What causes methicillin resistance in staph?

Answer 11

presence of the MecA gene

Question 12

Name two predisposing factors to diabetic foot ulcers

Answer 12

Neuropathy

Peripheral vascular disease- (slow healing)

Question 13

How do you treat infected diabetic foot ulcers?

Answer 13

Treat polymicrobial - usually they have been around for a long time and have been seeded with many different strains of bacterial

Question 14

Name 3 potentially fatal complications of cellulitis

Answer 14

Necrotizing fasciitis
Sepsis
Toxic Shock Syndrome (2% fatal)

Question 15

Describe the blood cultures of someone with staph toxic shock

Answer 15

Classically they are negative

Question 16

What is the clinical pictures of someone with toxic shock

Answer 16

Fever, hypotension
Macular erythematous rash
Multi-organ involvement
Later- desquamation of palms/soles

Question 17

Describe the pathogenesis of staph txx

Answer 17

TSS toxin -1 release –> massive cytokine production

Question 18

Differentiate the rash see in staph toxic shock vs strep toxic shock

Answer 18

Staph: diffuse rash
Strep: diffuse rash only seen in 10% of cases - more commonly positive cultures

Question 19

What is the clinical presentation of necrotizing fasciitis?

Answer 19

Pain out of proportion to exam
Rapidly evolving
Fever, hypotension
Skin: initially minimal changes –> dark/necrotic/gangrene

Question 20

What is unique about the pathogenesis of pseudomonas cellulitis/nodules?

Answer 20

Rather than coming from outside –> in, bacteremia with pseudomonas can cause septic emboli to the skin and cause necrotic nodules on the skin (inside out)