Bacterial infections of skin and soft tissue I

Question 1

Which pathogens are associated with diabetes?

Answer 1

S. aureus and GBS

Question 2

Which pathogen is associated with neutropenia and hot tub use?

Answer 2

Pseudomonas aeruginosa

Question 3

Which pathogens are associated with IV drug use?

Answer 3

MRSA, pseudomonas aeruginosa

Question 4

Which pathogen is associated with impetigo?

Answer 4

Strep pyogenes

Question 5

Impetigo is characterized by what type of skin lesion?

Answer 5

Honey crusted lesions and erosions often around mouth

Question 6

Which organism is associated with bullous impetigo?

Answer 6

Staph aureus

Question 7

What is responsible for the blisters seen in bullous impetigo?

Answer 7

Exfoliative toxin from staph aureus

Question 8

Which organism is responsible for ecthyma?

Answer 8

Strep pyogenes

Question 9

What type of lesion is characteristic of ecthyma?

Answer 9

Punched-out ulcerative lesions

Question 10

Which organism is most commonly responsible for a furuncle?

Answer 10

Staph aureus

Question 11

What is a furuncle?

Answer 11

Essentially a staph aureus abscess on a hair follicle

Question 12

What is a carbuncle?

Answer 12

Multiple furuncles coalescing and extending deeper into subcutaneous tissues

Question 13

What is the defining feature of a carbuncle?

Answer 13

Chills and fevers (sometimes systemic spread)

Question 14

Which organism is typically responsible for erysipelas?

Answer 14

Strep pyogenes (recent respiratory or skin infection)

Question 15

Cellulitis is most often caused by what organism?

Answer 15

GAS or staph aureus

Question 16

What is paronychia?

Answer 16

Localized, superficial infection or abscess of the nailfolds, lasting longer than 6 weeks and usually secondary to candida albicans infection

Question 17

What is the most common organism associated with paronychia?

Answer 17

Staph aureus

Question 18

What is the most common cause of necrotizing fasciitis?

Answer 18

Strep pyogenes

Question 19

What are the hallmarks of necrotizing fasciitis?

Answer 19

Toxicity, multi organ failure, death

Question 20

What is the gram stain for pseudomonas?

Answer 20

Gram negative

Question 21

What is the shape of pseudomonas?

Answer 21

Rod

Question 22

What is the coagulase test for staph aureus?

Answer 22

Positive

Question 23

What is the hemolysis pattern for staph aureus?

Answer 23

Beta

Question 24

What are the structural virulence factors for staph aureus?

Answer 24

Capsule, peptidoglycan, teichoic acid, protein A

Question 25

What is the role of the staph aureus virulence factor Protein A?

Answer 25

Turns Ab around so it can no longer link to a phagocyte (non-functional presentation, soaks up Abs)

Question 26

What virulence factor mediates staphylococcal scalded skin syndrome?

Answer 26

Exfoliative toxins

Question 27

Which enzymes serve as virulence factors in staph soft tissue infections?

Answer 27

Coagulase, hyaluronidase, fibrinolysin, lipases, nucleases

Question 28

Why is staph not culturable from the skin of a SSSS patient?

Answer 28

Toxin mediated disease

Question 29

Why are leukocytes not seen on the skin of a SSSS patient?

Answer 29

No inflammation involved - only blistering

Question 30

What kind of toxins are exfoliative toxins?

Answer 30

Serine proteases

Question 31

What is the function of exfoliative toxins?

Answer 31

Split desmoglein-1 and form intercellular bridges in the stratum granulosum epidermis

Question 32

What is Nikolsky sign?

Answer 32

In SSSS - lateral pressure on fingertips leads to sloughing off of skin

Question 33

Which antibiotics are resistant to beta lactamase hydrolysis?

Answer 33

Methicillin, oxacillin, nafcillin

Question 34

What gene confers resistance of staphylococcus to methcillin?

Answer 34

MecA

Question 35

Most is the most likely bacterial cause of ostetomyelitis?

Answer 35

Staph aureus

Question 36

What is the most likely cause of septic arthritis in children and adults receiving intraarticular injections?

Answer 36

Staph aureus

Question 37

What is the most likely cause of septic arthritis in sexually active adults?

Answer 37

Neisseria gonorrhea