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Flashcards in Staphylococci Deck (13):
1

Staphylococci general characteristics (6).

1. Gram positive.
2. Cocci in bunches.
3. Non-motile.
4. Catalase +.
5. Coagulase +/-.
6. Can grow in medium up to 10% NaCl.

2

Staphylococcus aureus (10):

1. Gram positive.
2. Cluster-forming coccus.
3. Nonmotile.
4. Non-spore forming.
5. Facultative anaerobe.
6. Ferments mannitol.
7. Catalase positive.
8. Coagulase positive.
9. Golden yellow colony on agar.
10. Normal flora of nares, skin and mucous membranes.

3

MRSA:

Methicillin Resistant Staph Aureus
- Mutated PCN binding protein.
- MecA gene.

4

Protein A (4):

- 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

Coagulase:

Converts fibrinogen to fibrin, protects bacteria under fibrin mesh.

6

Staphylococcal toxins (4):

- Cytolytic toxins.
- Exfoliative toxins.
- Enterotoxins.
- Toxic shock syndrome toxin - 1 (TSST-1).

7

Panton-Valentine Leukocidin (6):

- Active against PMNs and macrophages causing cell lysis.
- Makes S. aureus more resistant to phagocytosis.
- Necrotizing pneumonia.
- Airway bleeding.
- Erythroderma.
- Leukopenia.

8

Staphylococcus aureus infections (10):

1. Skin: impetigo, folliculitis, furuncles and carbuncles.
2. Wound infections.
3. Scalded skin syndrome (SSS).
4. Bullous impetigo: localized form of SSS.
5. Food poisoning.
6. Toxic shock syndrome (extended use of tampons).
7. Osteomyelitis (#1).
8. Infective arthritis (#1).
9. Acute endocarditis (#1).
10. Bacteremia and sepsis (#1).

9

Staphylococcal scalded skin syndrome:

- Perioral erythema covers entire body within 2 days.
- Positive Nikolsky's sign.
- Exfoliative toxin destroys the intracellular connections in the skin.

10

Bullous impetigo:

- Localized staph scalded skin syndrome.
- Culture positive.
- Negative Nikolsky's sign.
- Highly communicable.

11

Staph. aureus pneumonia:

- Aspiration pneumonia: Patchy infiltrates with consolidation or abscess.
- Hematogenous pneumonia from bacteremia or endocarditis.

12

Staphylococcus epidermidis (6):

1. Gram positive.
2. Cocci in clusters.
3. Coagulase negative.
4. Gloycocalyx.
5. Beta-lactamase
6. Mutant PCN-binding protein.

13

Staph. epidermidis virulence factors:

Glycocalyx: Exopolysaccharide "slime" helps in adhesion, antiphagocytosis and makes it resistant to antibiotics.