Ch.21: Microbial Diseases of the Skin

Question 1

What is a Staphylococcus species?

Answer 1

Gram-positive cocci (clusters); opportunistic pathogens

Question 2

What is S. epidermis?

Answer 2

-(coagulase-negative)
-nosocomial pathogen; possess slime layer
-can penetrate the skin via catheter insertion

Question 3

What is S. aureus?

Answer 3

-coagulase-positive, that possesses a number of virulence factors

Question 4

What is S. aureus virulence factors

Answer 4

-Toxins: anti-phagocyte
-Resist opsonization
-Neutralizes AMPs of Host
-Lysozyme resistant
-antibiotic-resistant (MRSA, VRSA)

Question 5

What are staphylococcal skin infections?

Answer 5

boils, carbuncles, impetigo, scalded-skin syndrome; toxic shock syndrome

Question 6

What is folliculitis

Answer 6

infection of the hair follicles

Question 7

what is a Sty

Answer 7

folliculitis of an eyelash

Question 8

What is a boil (Furuncle)

Answer 8

abscess; puss surrounded by inflamed tissue

Question 9

What is a carbuncle

Answer 9

inflammation of tissue under the skin

Question 10

What is impetigo

Answer 10

crusting (nonbullous) sores, spread by autoinoculation

Question 11

What is scalded skin syndrome?

Answer 11

form of impetigo (bullous) due to toxin; causes separation of skin layers

Question 12

what is a streptococcus species?

Answer 12

gram-positive cocci (in chains)

Question 13

How are streptococcus species characterized?

Answer 13

-appearance on blood agar
-classified based on hemolytic properties

Question 14

what is α (alpha) hemolysis?

Answer 14

green, partial hemolysis:
-(S. pneumoniae causes pneumonia meningitis)
-(Dental caries plaque biofilms endocarditis)

Question 15

What is β (Beta) hemolysis?

Answer 15

clear, complete hemolysis
(pyogenes that cause strep throat scarlet fever Necrotizing fascitis)

Question 16

What is γ (gamma) hemolysis?

Answer 16

NO hemolysis (enterococcus spp. rarely harmful)

Question 17

Streptococcus pyogenes are known for causing

Answer 17

sore throats

Question 18

What are the virulence factors for Streptococcus pyogenes?

Answer 18

-M protein: prevents complement activation: facilitates adherence
-Hyaluronic acid capsule: non-antigenic

Question 19

What do virulence factors in streptococcus pyogenes produce?

Answer 19

streptokinase, hyaluronidase, streptolysin, exotoxin A (superantigen)

Question 20

What is rheumatic fever

Answer 20

secondary immunological response (sequelae)

Question 21

What is an M protein in Rheumatic fever?

Answer 21

the body produces antibodies to M protein; these cross-react with heart muscle proteins

Question 22

What is Necrotizing fasciitis

Answer 22

-flesh-eating disease; deep tissue layers affected; toxins causes death of tissues, can affect muscles

Question 23

What is herpesvirus-varicella zoster?

Answer 23

-latent Viral skin disease: Chicken pox—> shingles
-acquired via the respiratory route and localizes in skin cells

Question 24

What does herpesvirus-varicella zoster form

Answer 24

a vesicular rash, then pustules