Staphylococcus

part of Study Guide #C1

Staphylococcus characteristics?

Gram positive, facultative anaerobe, grape-like clusters of cells

How does it distinguish from Streptococcus?

It is catalase positive

Hemolysis

The break down of red blood cells.

What are alpha, beta, and gamma hemolytic strains? 

Alpha = partly 

Beta = always 

Gamma = never 

What is an exotoxin?

Toxins that leave the body; secreted by bacteria.

What is a Superantigen?

a type of antigen that causes an extreme and widespread immune response by non-specifically activating a large number of T-cells

How does S. aureus infections begin?

S. aureus enters the blood and moves into the tissues, causing diseases.

S. aureus examples of infection…

Septic arthritis (joints), Endocartis (heart), Osteomyelitis ( bones)

What is Bacteremia and septic shock?

• Bacteremia is the bacterial infection in the blood (also called septicemia)

• it can be fatal —> body tried to fight against system-wide infection

  • Attempt at defense can lead to lethal decrease in Blood Pressure = Septic Shock

What is Toxic shock syndrome? What does it causes?

TSS = septic shock w/o sepsis( damage ot organs)

• When S. aureus builds up in tampons, large amounts of exotoxins are absorbed by the body = TSS

Causes = fever, rashes, vomiting, diarrhea, scalded skin syndrome 

What are the chains of events in S. aureus food poisoning?

1. S. aureus = halophilic(thrive sin salt), and grows at many temperatures.

2. gets into food

3. exotoxins are produced

4. exotoxins poison our gut —> even if bacteria is killed

What is the Hallmark effect? 

1. Rapid onset = few hours after eating 

2. Rapid Recovery = fully recovered within 1-2 days 

How is S. aureus infections treated?

Antibiotics, clean cuts with soap, handwashing, proper aseptic and antiseptic techniques.

What does MRSA stand for and why is it of medical concern?

MRSA = Methicillin Resistance Staphylococcus Aureus

• Concern = methicillin most chosen antibiotic = can resist many antibiotics

What are the best defenses against S. aureus infections? 

• Exotoxins = superantigen acts as a smoke screen

  • Host defenses are split up, confused by toxins; dangerous for host

• Protein A: binds to antibodies to prevent them form attacking the cell 

• Antibiotic resistance to penicillin and more

  • MRSA