Skin & soft tissue infections

Question 1

Define cellulitis

Answer 1

acute infection of the skin principally involving the dermis and subcutaneous tissue

Question 2

Etiology of cellulitis

• (2) common causative agents
• (2) risk factors

Answer 2

• S. aureus
• β-hemolytic streptococci

• immunocompromised patients: may also include GN rods and fungi
• risk factors:
ƒƒ- trauma with direct inoculation, recent surgery
ƒƒ- peripheral vascular disease, lymphedema diabetes, cracked skin in feet/toes (tinea pedis)

Question 3

Px of cellulitis

Answer 3

• pain, tenderness, edema, erythema with indistinct borders ± regional lymphadenopathy,
systemic symptoms (fevers, chills, malaise)

• can lead to ascending lymphangitis (visible red streaking in skin along lymphatics proximal to
area of cellulitis)

Question 4

Ix of cellulitis

Answer 4

• CBC and differential, blood C&S if febrile

* skin swab ONLY if open wound with pus

Question 5

Antibiotics of choice for cellulitis

Answer 5

Cephalexin (1st gen cephalosporin)

• if extensive erythema or systemic symptoms, consider cefazolin IV

Question 6

Mx of cellulitis

Answer 6

• antibiotics: cephalexin
• if extensive erythema or systemic symptoms, consider cefazolin IV
• limb rest and elevation may help reduce swelling

Question 7

Define necrotizing fasciitis

Answer 7

life- and limb-threatening infection of the deep fascia characterized by rapid spread

Question 8

Etiology of Define necrotizing fasciitis

• type I
• type II

Answer 8

ƒƒType I: polymicrobial infection – aerobes and anaerobes (e.g. S. aureus, Bacteroides,
Enterobacteriaceae)

ƒƒType II: monomicrobial infection with GAS

Question 9

Px of Define necrotizing fasciitis

Answer 9

• pain out of proportion to clinical findings and beyond border of erythema
• edema, ± crepitus (subcutaneous gas from anaerobes), ± fever
• infection spreads rapidly
• patients may rapidly become very sick (tachycardia, hypotension, lightheadedness)
• late findings:
ƒƒ- skin turns dusky blue and black (secondary to thrombosis and necrosis)
ƒƒ- induration, formation of hemorrhagic bullae

Question 10

Ix of Define necrotizing fasciitis

Answer 10

• a clinical/surgical diagnosis – do NOT wait for results of investigations before beginning
treatment
• blood and tissue C&S
• serum CK (elevated CK usually means myonecrosis – a LATE sign)
• plain film x-ray (soft tissue gas may be visualized)
• surgical exploration for debridement of infected tissue

Question 11

Rx of Define necrotizing fasciitis

Answer 11

• resuscitation with IV fluids
• emergency surgical debridements to confirm diagnosis and remove necrotic tissue
• IV antibiotics

Question 12

Antibiotics of choice for unknown organism necrotizing fasciitis

Answer 12

meropenem or piperacillin/tazobactam + clindamycin IV ± vancomycin
if MRSA is considered

Question 13

Antibiotics of choice for type I (polymicrobial) necrotizing fasciitis

Answer 13

piperacillin/tazobactam + clindamycin IV

Question 14

Antibiotics of choice for type II (monomicrobial) necrotizing fasciitis

Answer 14

penicillin G + clindamycin IV

with Type II, evaluate for streptococcal toxic shock syndrome and the need for IVIG