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Lecture 24

BIOL 1353 Lecture Notes - Lecture 24: Staphylococcus, Hospital-Acquired Infection, Streptococcal Pharyngitis

Course Code
BIOL 1353

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Chapter 21 Microbial diseases of the Skin
Staphylococcus species: gram-positive cocci (clusters); opportunistic pathogens
- S. epidermidis (coagulase negative); nosocomial pathogen; possess slime layer
o Can penetrate skin via catheter insertion
o Benign strain, but can be opportunistic
o Can form biofilms
o Not a common nosocomial infection
- S. aureus (coagulase positive); possesses a number of virulence factors
o Toxins: anti-phagocyte. Leukocidins
o Resists opsonization
o Neutralizes AMPS of host
o Lysozyme resistant
o Antibiotic resistant (MRSA, VRSA)
o About 20% of the population carries this, and 60% of us have had it at some
o Protease A neutralizes the antibody
- Staphylococcal skin infections
o Folliculitis: infection of the hair follicles
o Sty: folliculitis of eyelash
o Furuncle (boil): abscess; pus surrounded by inflamed tissue
o Carbuncle: inflammation of tissue under skin
o Impetigo: crusting (nonbullous) sores, spread by autoinoculation
o Scalded skin syndrome: form of impetigo (bullous) due to toxin; causes
separation of skin layers. Relatively mild and most common in newborns to 1
year old.
Streptococcus species: gram-positive cocci (in chains)
- Classified based on their hemolytic properties (via hemolysins)
- Culture streptococci on blood agar
o Alpha hemolysis: partial hemolysis
S. pneumoniae
Pneumonia, meningitis
Viridans: S. mutans
Dental caries
Infecting hemoglobin, green color
o Beta hemolysis: complete hemolysis
GAS S. pyogenes (means all group A streptococcus can cause this)
Strep throat
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