Skin and Soft Tissue infections

Question 1

main causes for SSTI

Answer 1

S. aureus, S. pyogenes (Group A Strep)

Question 2

most common presentation of SSTIs

Answer 2

acute; rubor, calor, tumor, dolor

Question 3

most likely route of infection in chronic inflammation

Answer 3

hematogenous with intracellular organisms

Question 4

Normal resistance mechanisms of skin to infection

Answer 4

physical & chemical barriers; innate immunity

Question 5

Special circumstances of SSTI:

Answer 5

puncture wounds, penetrating trauma, bites

Question 6

special patient populations for SSTIs

Answer 6

young, old, immunocompromised, diabetic, underlying skin disease, patients in health care facilities

Question 7

Principles of SSTI treatment:

Answer 7

• local hygienic care/incision and drainage (removal of pus)
• antibiotic coverage for suspected organisms depending on sensitivity (if systemic signs are present on PE, are special circumstances or special patient population)

Question 8

skin infections (2)

Answer 8

erysipelas (epidermis); cellulitis (dermis)

Question 9

host defense involves:

Answer 9

anatomy; immunology; microbiology

Question 10

gram positive pus organisms:

Answer 10

strep or staph

Question 11

catalase test is used for gram positive or negative?

Answer 11

gram positive

Question 12

indications for coagulase test

Answer 12

gram positive catalase positive staphylococci

Question 13

catalase positive coagulase positive

Answer 13

staph aureus

Question 14

catalase positive, coagulase negative

Answer 14

coagulase negative staph (staph epidermidis)

Question 15

strep pyogenes

Answer 15

catalase negative streptococci, beta hemolysis

Question 16

catalase negative, beta hemolysis

Answer 16

strep pyogenes, group a, b, c, g, strep

Question 17

indications for hemolysis

Answer 17

catalase negative strep

Question 18

indications for oxidase test

Answer 18

gram negative rods and cocci

Question 19

oxidase positive rod

Answer 19

pseudomonas

Question 20

oxidase positive cocci

Answer 20

neisseria

Question 21

strep pyogenes (group A) virulence factors:

Answer 21

1. structural (Group A capsule, M protein, LTA)
2. exo-toxins (pyrogenic exotoxin A & C, SA >TSS, scarlet fever); (streptolysins A & O, hemolysins - beta, iron acquisition)

Question 22

staph aureus virulence factors

Answer 22

1. structural (protein A - binds IgG = antiphagocytic; coagulase - cleaves fibrinogen)
2. exotoxins: TSST-1 (SA in TSS); PVL (bacteriophage in MRSA); exfoliative toxin (SSS)

Question 23

TSST-1 is VF in:

Answer 23

staph aureus

Question 24

pyrogenic exotoxin A & C are VF in:

Answer 24

strep pyogenes (GAS)

Question 25

USA 300

Answer 25

most common CA-MRSA; has separate genetic elements coding for MecA and PVL; CA SSTI clinically

Question 26

less common causes of SSTI

Answer 26

• normal flora (percutaneous cather)
• gram - bacteria (special pt groups)
• beta hemolytic strep (newborns, diabetics)
• fungi (pts on broad-spectrum abs or immunocompromised)

Question 27

causes for SSTI in newborns

Answer 27

beta hemolytic strep, gram negative bacteria

Question 28

pathogenesis of SSTI

Answer 28

1. trans-epidermal or

2. hematogenous