Staphylococci Flashcards
1
Q
Staphylococci general characteristics (6).
A
- Gram positive.
- Cocci in bunches.
- Non-motile.
- Catalase +.
- Coagulase +/-.
- Can grow in medium up to 10% NaCl.
2
Q
Staphylococcus aureus (10):
A
- Gram positive.
- Cluster-forming coccus.
- Nonmotile.
- Non-spore forming.
- Facultative anaerobe.
- Ferments mannitol.
- Catalase positive.
- Coagulase positive.
- Golden yellow colony on agar.
- Normal flora of nares, skin and mucous membranes.
3
Q
MRSA:
A
Methicillin Resistant Staph Aureus
- Mutated PCN binding protein.
- MecA gene.
4
Q
Protein A (4):
A
- Present on the surface of most S. aureus.
- Covalently linked with the peptidoglycan layer.
- Unique affinity to bind the Fc portion of IgG.
- Resists opsonization and phagocytosis.
5
Q
Coagulase:
A
Converts fibrinogen to fibrin, protects bacteria under fibrin mesh.
6
Q
Staphylococcal toxins (4):
A
- Cytolytic toxins.
- Exfoliative toxins.
- Enterotoxins.
- Toxic shock syndrome toxin - 1 (TSST-1).
7
Q
Panton-Valentine Leukocidin (6):
A
- Active against PMNs and macrophages causing cell lysis.
- Makes S. aureus more resistant to phagocytosis.
- Necrotizing pneumonia.
- Airway bleeding.
- Erythroderma.
- Leukopenia.
8
Q
Staphylococcus aureus infections (10):
A
- Skin: impetigo, folliculitis, furuncles and carbuncles.
- Wound infections.
- Scalded skin syndrome (SSS).
- Bullous impetigo: localized form of SSS.
- Food poisoning.
- Toxic shock syndrome (extended use of tampons).
- Osteomyelitis (#1).
- Infective arthritis (#1).
- Acute endocarditis (#1).
- Bacteremia and sepsis (#1).
9
Q
Staphylococcal scalded skin syndrome:
A
- Perioral erythema covers entire body within 2 days.
- Positive Nikolsky’s sign.
- Exfoliative toxin destroys the intracellular connections in the skin.
10
Q
Bullous impetigo:
A
- Localized staph scalded skin syndrome.
- Culture positive.
- Negative Nikolsky’s sign.
- Highly communicable.
11
Q
Staph. aureus pneumonia:
A
- Aspiration pneumonia: Patchy infiltrates with consolidation or abscess.
- Hematogenous pneumonia from bacteremia or endocarditis.
12
Q
Staphylococcus epidermidis (6):
A
- Gram positive.
- Cocci in clusters.
- Coagulase negative.
- Gloycocalyx.
- Beta-lactamase
- Mutant PCN-binding protein.
13
Q
Staph. epidermidis virulence factors:
A
Glycocalyx: Exopolysaccharide “slime” helps in adhesion, antiphagocytosis and makes it resistant to antibiotics.