S. Auerus

Question 1

1) classification

Answer 1

Family:
Genus: staphylococcus aureus

Coagulase positive

• 30% of people are carriers:
  >perineum
  >Axillae
  >nose

Spread via direct contact

Question 2

2) morphology

Answer 2

• Gram positive cocci

- irregular grape like clusters

Question 3

3) growth characteristics

Answer 3

• facultative anaerobes
• non-fastidious
• 37oC (10 - 40 oC)
• grow at 10% NaCl

Question 4

4) antigenic structure

Answer 4

Polysaccharide capsule (rare)
Teichnoic acid
Peptidoglycan
Protein A

Triple P

Question 5

5) virulence factor

Answer 5

Enzymes:

B-lactamases 
Coagulase
Fibrolysin 
Hyaluronidase
Nucleases 

Toxins:
Leucocidin
Exfoliating toxins
Enterotoxins
Toxic shock syndrome toxin 1 
Hemolysin

Question 6

6) Disease

Answer 6

> pyogenic localized infections:

Impetigo
Furuncles
Abscesses

> bacteremia and disseminated infections: 
Osteomyelitis
Endocarditis
Meningitis 
Pulmonary infections

> disease due to staphylococcal toxins:
Scalded skin syndrome (exfoliating toxins)
Toxic shock syndrome (mediated by TSST 1)
Staphylococcal food poisoning

Question 7

7) microbiological diagnosis

Answer 7

Cultures:

Blood agar plate: gold-yellow colonies with в-hemolysis

Specific tests:
Catalase positive
Clumping factor test positive
Tube coagulase test positive

Question 8

8) treatment and prevention

Answer 8

> more than 90% resistant strains to penicillin
- mediated by b-lactamase (penicilase)

• encoded by transmissible plasmid
  > they are susceptible to b-lactamase-resistant penicillin, cephalosporins and vancomycin

> resistance strains to penicilinase-resistant penicillin (methicillin-resistant):
More than 30% in S.aureus
More than 40% in CNS:
Due to alterations in PBPs