Skin Infections and Treatment

Question 1

Superficial folliculitis

Answer 1

Single hair follicle, purulent, erythematous, does not extend into dermis

Question 2

Deep folliculitis

Answer 2

Extends into dermis

Question 3

Furuncle

Answer 3

Red, tender nodule surrounding follicle with single drainage point

Question 4

Carbuncle

Answer 4

Deep follicular abscess of several follicles with several draining points

Question 5

Cutaneous abscess

Answer 5

Invades deep through dermis and into subcutaneous tissue with pocket of pus inside of it, may have spontaneous drainage source

Question 6

If infection is purulent, always think…

Answer 6

STAPH AUREUS

Question 7

Management of purulent infections

Answer 7

First line: Incision and drainage
Second line: antibiotics
- do 2nd line if: large abscess, multiple abscesses, in hard to drain areas, extensive cellulitis, immunosuppression/comorbidities, systemic toxicity, poor clinical response to incision/drainage alone

Question 8

Empiric antibiotics for purulent infections

Answer 8

Relatively healthy patient: TMP-SMX or doxycycline (PO)
Immunocompromised/septic pt (temp >38, HR>90, RR>24,WBC>12000 or <400cells/uL): vancomycin (2nd line = daptomycin or linezolid)

Question 9

Directed antibiotics for purulent infections

Answer 9

If MRSA: no change needed

If MSSA: Cloxacillin (2nd line: cefazolin)

Question 10

Non-bullous impetigo

Answer 10

Common in children, staph aureus >group a strep

Tx: Topical Abx (Mupirocin) or oral Abx (cephalexin)

Question 11

Bullous impetigo

Answer 11

Common in neonates, toxin-producing staph aureus
Tx: Cephalexin PO, Cefazolin IV; vancomycin if risk of MRSA
At risk of dehydration and sepsis

Question 12

Erysipelas

Answer 12

Erythematous, raised, well-demarcated infection limited to UPPER DERMIS and SUPERFICIAL LYMPHATICS) often on face
Rapid onset, fever, systemic toxicity

Question 13

Erysipelas microbiology

Answer 13

Almost always group A strep

Question 14

Erysipelas tx

Answer 14

Oral: Penicillin, amoxicillin (Group A strep specific)
IV: Penicillin, Cefazolin

Question 15

Cellulitis

Answer 15

Break in skin causing normal skin flora to invade dermis and subcutaneous tissue; commonly in lower extremities
Simple/localized: normal WBC, no systemic symptoms, lymphadenopathy/lymphangitis common
Severe (can travel up lymphatic chain and spread): systemic symptoms, bullae, hemorrhage, severe swelling

Question 16

Cellulitis microbiology

Answer 16

Group A strep

Staph aureus less common (usually IVDU, penetrating trauma, open wounds)

Question 17

Empiric cellulitis tx

Answer 17

Healthy patient: Cephalexin or penicillin
Systemic toxicity/immunocompromised/failed oral abx: cefazolin IV
Signs of sepsis (low BP, organ dysfunction) and/or signs of necrotizing fasciitis(bullae, skin sloughing, rapid spread): piperazillin-tazobactam AND vancomycin
Surgical evaluation

Question 18

Septic arthritis

Answer 18

Clinical triad: fever, pain and decreased ROM
Dx: Synovial fluid (>50 000 WBCs, gram stain/culture +), blood cultures + since often hematogenous spread, x-ray to rule out associated osteomyelitis

Question 19

Septic arthritis microbiology

Answer 19

Staph aureus&raquo_space; strep > gram -ve organisms >mycobacteria/fungi

Question 20

Tx of septic arthritis

Answer 20

AFTER joint aspiration 
Based on gram stain results:
Gram + cocci --> vancomycin 
Gram - cocci --> ceftriaxone 
Gram stain negative or mixed --> vancomycin AND ceftriaxone 
IV for at least 4 wks 
Surgical drainage

Question 21

Prosthetic joint infections

Answer 21

Biofilm formation

Question 22

Prosthetic joint infection epidemiology

Answer 22

Staph aureus is common culprit

Question 23

Prosthetic joint infection tx

Answer 23

IV antibiotics for at least 6 weeks followed by oral antibiotic for 4 months if prosthesis is NOT removed
Rifampin throughout (adjunctive tx)
Surgery: Prosthesis removal vs debridement/retention

Question 24

Common bacteria associated with cat bite

Answer 24

Pastuerella multocida

Question 25

Common bacteria associated with dog bite

Answer 25

Pastuerella canis

Question 26

Tx for animal bites

Answer 26

Amoxillin-clavulanate (MUST BE BROAD SPECTRUM)

Question 27

Give tetanus vaccine if…

Answer 27

Minor wound and no vaccine in 10yrs

Or major would and no vaccine in 5yrs

Question 28

Give tetanus Ig if…

Answer 28

Major wound and did not receive at least 3 tetanus doses

Question 29

Rabies

Answer 29

Very rare in vaccinated domestic pets
Rabies vaccine on days 0, 3, 7, 14 –> ramps up viral response while virus is growing
Rabies Ig around wound

Question 30

Tx for mildly infected diabetic wound

Answer 30

Cephalexin +/- TMP-SMX to cover strep and staph

Question 31

Tx for moderately infected diabetic wound

Answer 31

Amoxacillin-clavulanate +/-TMP SMX to cover strep and staph and gram -ves/anaerobes

Question 32

Tx for severely infected diabetic wound

Answer 32

Piperacillin-Tazobactam AND vancomycin to cover strep and staph and gram -ves/anaerobes

Question 33

Best treatment for MSSA

Answer 33

Cloxacillin

Question 34

Empiric Tx for necrotizing fasciitis

Answer 34

Source control (surgical debridement) 
Vancomycin (MRSA) + Pip-Tazo +/- clindamycin

Question 35

Tx for Group A Strep NF/STSS

Answer 35

Penicillin IV + Clindamycin IV

2-3wks

Question 36

Benefit of using clindamycin in Group A strep

Answer 36

Blocks protein production (blocks M protein production)

Active against non-actively growing bacteria, whereas penicillin is only active against growing bacteria

Question 37

Empiric tx for staphylococcal toxic shock

Answer 37

Supportive care for shock
Source control
Vancomycin (MRSA) + clindamycin (can step down to cloxacillin if MSSA confirmed)

Question 38

Adjunctive tx for NF/STTS

Answer 38

IV immunoglobulin (IVIG) 1g/kg day 1 and 0.5g/kg day 2-3 
Pooled antibiotics from large pool of donors

Question 39

Tx for osteomyelitis

Answer 39

Cefazolin IV