Ch.21: Microbial Diseases of the Skin Flashcards
What is a Staphylococcus species?
Gram-positive cocci (clusters); opportunistic pathogens
What is S. epidermis?
-(coagulase-negative)
-nosocomial pathogen; possess slime layer
-can penetrate the skin via catheter insertion
What is S. aureus?
-coagulase-positive, that possesses a number of virulence factors
What is S. aureus virulence factors
-Toxins: anti-phagocyte
-Resist opsonization
-Neutralizes AMPs of Host
-Lysozyme resistant
-antibiotic-resistant (MRSA, VRSA)
What are staphylococcal skin infections?
boils, carbuncles, impetigo, scalded-skin syndrome; toxic shock syndrome
What is folliculitis
infection of the hair follicles
what is a Sty
folliculitis of an eyelash
What is a boil (Furuncle)
abscess; puss surrounded by inflamed tissue
What is a carbuncle
inflammation of tissue under the skin
What is impetigo
crusting (nonbullous) sores, spread by autoinoculation
What is scalded skin syndrome?
form of impetigo (bullous) due to toxin; causes separation of skin layers
what is a streptococcus species?
gram-positive cocci (in chains)
How are streptococcus species characterized?
-appearance on blood agar
-classified based on hemolytic properties
what is α (alpha) hemolysis?
green, partial hemolysis:
-(S. pneumoniae causes pneumonia meningitis)
-(Dental caries plaque biofilms endocarditis)
What is β (Beta) hemolysis?
clear, complete hemolysis
(pyogenes that cause strep throat scarlet fever Necrotizing fascitis)
What is γ (gamma) hemolysis?
NO hemolysis (enterococcus spp. rarely harmful)
Streptococcus pyogenes are known for causing
sore throats
What are the virulence factors for Streptococcus pyogenes?
-M protein: prevents complement activation: facilitates adherence
-Hyaluronic acid capsule: non-antigenic
What do virulence factors in streptococcus pyogenes produce?
streptokinase, hyaluronidase, streptolysin, exotoxin A (superantigen)
What is rheumatic fever
secondary immunological response (sequelae)
What is an M protein in Rheumatic fever?
the body produces antibodies to M protein; these cross-react with heart muscle proteins
What is Necrotizing fasciitis
-flesh-eating disease; deep tissue layers affected; toxins causes death of tissues, can affect muscles
What is herpesvirus-varicella zoster?
-latent Viral skin disease: Chicken pox—> shingles
-acquired via the respiratory route and localizes in skin cells
What does herpesvirus-varicella zoster form
a vesicular rash, then pustules
