Skin and Soft Tissue Infections - Key Organisms

Question 1

Impetigo most common organisms

Answer 1

Staphylococcus aureus and/or

Streptococcus pyogenes (Group A streptococcus)

Question 2

Erysipelas (variant of cellulitis)

Answer 2

beta-hemolytic streptococci

Question 3

Cellulitis (children)

Answer 3

S. pyogenes

S. aureus (primarily MSSA)

Group B strep in neonates

Question 4

Cellulitis (adults, post operative)

Answer 4

S. aureus (including MRSA in some)

S. pyogenes

Other group strep

Question 5

Cellulitis (Injection Drug Users)

Answer 5

S. aureus (including MRSA)

S. pyogenes

anaerobes

Viridans (not common, this typically found in the mouth)

Question 6

Cellulitis (Diabetics)

Answer 6

S. aureus

S. pyogenes

Group B strep

Gram negative bacilli

Question 7

Cellulitis (Immunocompromised)

Answer 7

S. aureus

S. pyogenes

Gram negative bacili

Question 8

CA MRSA acquires _______ which causes ______

Answer 8

MecA

Difference in penicillin binding protein

Question 9

CA MRSA contain unique virulence genes such as

Answer 9

exotoxins: Panton - Valentine leukocidin (PVL) responsible for tissue necrosis and abscess

Question 10

For cellulitis, empiric therapy should be directed against BOTH

Answer 10

Staphylococcus aureus (MSSA) and group A strep (Streptococcus pyogenes)

Question 11

Beta hemolytic streptococcus aka

Answer 11

Streptococcus pyogenes

aka

Group A strep

Question 12

In cellulitis, suspect MRSA in patients

Answer 12

*who have the spreading skin infection with an abscess right in the middle

penetrating trauma

*evidence of MRSA elsewhere

Injection drug user

Question 13

If infecting organisms is known: Strep pyogenes

[Tx of cellulitis]

Answer 13

Penicillin

Question 14

If infecting organisms is known: MRSA

[Tx of cellulitis]

Answer 14

Bactrim

clindamycin (PO)

vancomycin (IV)

Question 15

If infecting organisms is known: Gram negative

[Tx of cellulitis]

Answer 15

3rd generation cephalosporin

extended spectrum penicillin

or FQ

Question 16

If infecting organisms is known: Polymicrobial

[Tx of cellulitis]

Answer 16

Zosyn

carbapenems

Question 17

Necrotizing Fasciitis (monomicrobial)

Answer 17

***Group A Streptococcus pyogenes (toxin producing strain)

S. aureus

Vibrio vulnificus (water from shellfish)

Aeromonas hydrophila

Question 18

Necrotizing Fasciitis (polymicrobial)

Answer 18

Mixed infection involving aerobes and anaerobes from the GI or GU tract

Question 19

Diabetes Foot Infection (DFI) - MILD

Answer 19

Streptococcus pyogenes and/or staph. aureus (MSSA unless patient has MRSA risk factors)

Question 20

Diabetes Foot Infection (DFI) - MODERATE

Answer 20

Streptococcus pyogenes and/or staph. aureus (MSSA unless patient has MRSA risk factors)

also consider obligate anaerobes if patient has necrotic wound that has not been debrided (removed)

Question 21

Diabetes Foot Infection (DFI) - SEVERE

Answer 21

Streptococcus pyogenes, Staph aureus (MSSA and MRSA), enterobacteriaceae, P. aeruginosa, anaerobes