Lecture 4 - Gram Positive Cocci (STAPH)

Question 1

Staphylococci

Answer 1

• Arranged in clusters

Question 2

Staphylococcus in humans

Answer 2

• Staphylococcus epidermis
• Staphylococcus aureus
• Staphylococcus saprophyticus

Question 3

Staphylococcus epidermis

Answer 3

normal flor of the skin, occasionally pathogenic

Question 4

Staphylococcus aureus:

BASIC

Answer 4

pathogenic, often found as normal flora

exotoxins are the issue

Question 5

Staphylococcus saprophyticus

Answer 5

found in the environment and on the skin,

can cause UTI

Question 6

Staphylococcus aureus:

Growth

Answer 6

• Grows on simple media (blood and agar)

- Produced 2-3 mm colonies in 24 hours at 37c

Question 7

Staphylococcus aureus:

Toxins

Answer 7

• Cytotoxins (breaks down body cells)
• Haemolysins (lyse RBC)
• Enterotoxin (A-E, G-I) super antigens
• Exfoliative toxins (ETA, ETB )
• Toxic shock syndrome toxin 1 (used to be exotoxin C and enterotoxin F)

Question 8

Staphylococcus aureus:

Enzymnes: Coagulase

Answer 8

• (coagulation of fibrin)
• made by almost all pathogenic staphylococci
• used in laboratory test to differentiate from S. epidermidis, S. capitis and S. saprophyticus

Question 9

Staphylococcus aureus:

Enzymnes: Beta-Lactamase

Answer 9

• (penicillinase)

- destroys penicillin

Question 10

Staphylococcus aureus:

and the population

Answer 10

• Many S. aureus strains are found in normal population (~15%)
• Carried in anterior nares, axilla, perineum and hands

Question 11

Staphylococcus aureus:

Problem in the Population

Answer 11

• 85-90% of strains isolated in hospital are penicillin resistant!!!
• Localized purulent infections (pustules, boils, styes, conjunctivitis,
  otitis, etc.)
• Pneumonia, osteomyelitis, septicaemia, endocarditis
• Food poisoning, toxic shock syndrome, scalded skin syndrome

Question 12

Staphylococcus aureus:

Preventative measures include

Answer 12

• Aseptic technique in ER and OR, wound precaution
• Education of health personnel
• Hand washing!

Question 13

Staphylococcus epidermis:

Answer 13

• Part of normal skin/mucous membrane flora
• Non-pathogenic, except in compromised patients where can cause post-operative infections (brain, open heart, endocarditis, shunt infections)
• Considered an opportunistic pathogen

Question 14

TSS

Answer 14

• can also occur in boys