Staphylococcus Aureus Flashcards
What are the general properties of Staphylococcus Aureus
Gram + cocci in clusters
Catalase +
Coagulase +
Beta hemolytic
Yellow on mannitol agar
Halotolerant
Where does it live in nature?
On people.
External Nares
Transiently on skin, oropharynx and perineum
50-80% carriage in healthcare workers
Transmission
Person to person
Hand to hand contact
Fomites
Types of Staph A infections
Pyogenic and toxigenic
List the pyogenic staph a diseases.
Boils and Furuncles
Cellulitis
Carbuncle
Impetigo
Folliculitis
Endocarditis (R sided IV drug users - tricuspid valve)
Septic Arthritis (most common cause of joint infection in adults)
Osteomyelitis (most common cause in adults)
Pneumonia
List at least (5) S. aureus virulence factors
Techoic Acid
Fibrinolysin
Lipase
Hyaluronidase
Nucleases
Capsule
Protein A
Catalase
Coagulase
Peptidoglycan
Cytotoxins
Enterotoxins
Beta lactamase
Methicillin resistance
Virulence factor: Techoic Acid
Found in gram +
Facilitates adherence
Virulence factor: Fibrinolysin
Inactivates fibrin
Helps with pathogen invasion
Virulence factor: Hyaluronidase
Breakdown hyaluronic acid in the cell wall of animal cells.
Helps with pathogen invasion
Virulence factor: Lipase
Breakdown cell membranes and tissues
Virulence factor: Nucleases
Virulence factor: Capsule
Inhibits phagocytosis
Facilitates adherence
Virulence factor: Protein A
Binds to Fc region of immunoglobulin (IgG)
Inhibits binding of phagocytes (thereby preventing opsonization)
Inhibits complement activation
Virulence factor: Catalase
Converts peroxide to water thereby counteracting neutrophil’s attempt to kill bacteria by producing free radicals
Virulence factor: Coagulase
Clots plasma
Fibrinogen to fibril
Bacteria hide there because white cells, abs and even abx dont penetrate clots well.
Virulence factor: Peptidoglycan
Endotoxin like activity
attracts leukocytes
Virulence factor: Cytotoxins
Membrane damaging (pore forming) toxins that lyse eukaryotic cells including neutrophils
Virulence factor: Enterotoxins
A and B induce vomiting
staphylococcal food poisoning
Virulence factor: TSST-1
Causes toxic shock syndrome
Virulence factor: Exfoliative Toxins A and B
Scalded skin syndrome in neonates
Bollus impetigo
Breaks down desmoglein- 1 (desmosomes) in stratum spinosum
Virulence factor: Beta lactamase
Enzyme that degrades antibiotics in the penicillin family
Virulence factor: Methicillin Drug Resistance
Due to mutated PDP (Penicillin binding protein)
Prevents the binding of beta lactam
List the toxigenic staph diseases.
Food poisoning (more vomiting than diarrhea)
Toxic shock syndrome
Scalded skin syndrome
Bullous Impetigo
