Bacterial Skin Infections

Question 1

Microbiota varies from site to site due to

Answer 1

differences in moisture content and the presence of sebaceous glands

Question 2

What conditions do pathogens prefer?

Answer 2

Alkaline moist conditions

Question 3

What does Propionibacterium acnes like?

Answer 3

Sebaceous glands (can metabolize sebum)

Question 4

Skin is normally dry, which decreases

Answer 4

bacterial colonization

Question 5

What are distinguishing features of S. pyogenies?

Answer 5

• G + cocci in chains
• Beta hemolytic
• Catalase negative
• Bacitracin sensitive

Question 6

Distinguishing factors of S. aureus

Answer 6

• G + cocci in clusters
• Beta hemolytic
• Catalase positive
• Coagulalse positive

Question 7

What gene does MRSA contain?

Answer 7

mecA that encodes an alternative penicillin binding protein

Question 8

MRSA is resistant to

Answer 8

all beta-lactam antibiotics

Question 9

Which is more virulent- community assoc MRSA or hospital?

Answer 9

Community associated

Question 10

L-arginine gets degraded and what is the byproduct?

Answer 10

ammonia

Question 11

Ammonia protects from

Answer 11

acidity of skin

Question 12

S. aureus avoids ________ made as a result of L-ornithine speG?

Answer 12

polyamines

Question 13

How does impetigo start?

Answer 13

With one or more sores, which are often itchy

Question 14

How is impetigo treated?

Answer 14

Topical antibiotics

Question 15

What is erysipelas?

Answer 15

Infection characterized by redness and warmth of the skin with a defined edge and is palpable

Question 16

What tissues are involved in erysipelas?

Answer 16

Epidermis and upper layer of dermis

Question 17

What is the most common cause of boils/abcesses?

Answer 17

S. aureus

Question 18

Steps leading to infection for boils/abcesses

Answer 18

• Colonization
• Dissemination to skin
• Minor local trauma
• Rapid progression to subcutaneous abscess
• High pus production (although they can have no pus too)

Question 19

What are the virulence factors associated with boils?

Answer 19

• Fibronectin binding proteins (adherence to fibronectin)
• Protein A (binds Fc portion of IgG to protect from phagocytosis)
• Coagulase (induces fibrin clotting on the bacteria protecting the cell from phagocytosis)

Question 20

How is cellulitis characterized?

Answer 20

By acute onset of redness, warmthm tenderness

Question 21

If cellulitis is acute onset and has a raised edge, it is most likely

Answer 21

S. pyogenes

Question 22

If cellulitis is slower onset and subtle edge, it can be

Answer 22

S. pyogenes or S. aureus

Question 23

Describe fasciitis

Answer 23

• Infection spreads in a plane parallel to the skin
• Spares underlying muscle
• May have limited visible redness

Question 24

Necrotizing fasciitis can be life threatening and often produces

Answer 24

pain out of proportion to the visible redness

Question 25

Necrotizing fasciitis is often accompanied by

Answer 25

fever and evidence of toxic appearance. Gas bubbles may form

Question 26

In necrotizing faciitis, what is used to interrupt production of toxins?

Answer 26

Clindamycin

Question 27

What is the most common cause of Necrotizing fasciitis?

Answer 27

S. pyogenes