Lecture 7 Staphylococcus

Question 0

What is the major location for S. aureus

Answer 0

In the nasal cavity

Question 1

What are the 3 major Staph that are pathogens and cause most of the disease?

Answer 1

S. aureus
S. epidermidis
S. saprophyticus

Question 2

Major location for S. epidermidis?

Answer 2

Dry skin or epithelium

Question 3

Major location for S. saprophyticus

Answer 3

Mucosa, Moist epithelium

Question 4

Which of the three Staph organisms are Coagulase +?

Answer 4

S. aureus

Question 5

4 main characteristics of S. aureus

Answer 5

1. Coagulase +
2. Protein A, many secreted enzymes and toxins
3. Frequently Drug Resistant (MRSA)
4. Involved in many illnesses such as Food poisoning, Toxic Shock etc.

Question 6

4 characteristics of S. epidermidis

Answer 6

1. No Coagulase
2. Capsule
3. Frequently drug resistant
4. Catheter and prosthetic implant infections

Question 7

2 characteristics of S. saprophyticus

Answer 7

1. No Coagulase

2. Urinary tract infections in young women

Question 8

What is the #2 cause of UTI’s in women?

Answer 8

S. saprophyticus

Question 9

Does S. aureus have a high carrier rate?

Answer 9

Yes, it is found in 20-30% of general population at any one time. Carrier rate is higher in Hospital Personnel

Question 10

Some isolates of S. aureus have become resistant to almost all antibiotics except what?

Answer 10

Vancomycin

Question 11

Name the 6 virulence factors on S. aureus

Answer 11

1. Fibrin binding proteins on cell wall that help colonize cells and tissues
2. Protein A
3. Many enzymes secreted
4. Cytolytic toxins
5. Superantigen exotoxins
6. Catalase +

Question 12

How is catalase a virulence factor for S. aureus

Answer 12

Catalase is able to convert the H2O2 secreted by PMN’s and allow S. aureus to survive

Question 13

What type of toxin is associated with Scalded Skin Syndrome in children

Answer 13

Exfoliative Toxin

Question 14

How do catalytic toxins work?

Answer 14

They lyse most cells, including host defense cells

Question 15

Superantigens (virulence factor) stimulate cytokine production which produces what two illnesses?

Answer 15

1. ‘True’ Food poisoning

2. Toxic Shock syndrome

Question 16

What is the name of the Superantigen that produces Toxic Shock Syndrome?

Answer 16

Toxic Shock Syndrome toxin (TSST-1)

Question 17

How does Protein A work?

Answer 17

It binds to the IgG Fc site, this blocks the phagocyte adherence to IgG opsonization

Question 18

How does Coagulase work as a virulence factor

Answer 18

produces local fibrin deposition that can act to wall off the infection

Question 19

Difference between secreted coagulase and surface coagulase

Answer 19

• Surface coagulase coats the staph cells with host fibrin, hiding bacterial epitopes and camoflaging itself from immune system
• Secreted coagulase produces local fibrin deposition that acts as a wall around the bacteria and restrict immune system from entering. This often leads to an abcess

Question 20

What leads to an abcess?

Answer 20

When Fibrin is deposited by a bacteria and acts to wall off the bacteria from the body and immune system.

Question 21

Name 3 specific spreading factors

Answer 21

Staphylokinase
Lipase
Hyaluronidase

Question 22

4 types of local infection caused by S. aureus

Answer 22

Local Skin infections
Deep, localized infections
Acute Endocarditis
Pneumonia

Question 23

Local skin infections may lead to what?

Answer 23

Cellulitis and Bacteremia

Question 24

2 examples of Local skin infection

Answer 24

Abscesses (boils, carbuncles) | Impetigo

Question 25

3 examples of Deep, localized infections

Answer 25

Abscesses of the spleen, liver and kidney Osteomyelitis Septic Arthritis

Question 26

Explain Scalded skin syndrome

Answer 26

An exfoliative toxin (protease) degrades desmosomes releasing the outer layer of epidermis. Rarely fatal and occurs in small babies

Question 27

Explain 'True' Food poisoning

Answer 27

Enterotoxins (superantigen) acting directly or indirectly on the GI tract to induce diarrhea and vomiting. Toxin does the poisoning not the bacteria

Question 28

What occurs during the Toxic Shock syndrome

Answer 28

Superantigen TSST-1 can be released from a focal infection, most commonly next to a mucosal surface. This toxin activates huge numbers of Th cells and macrophages that release cytokines. This massive release of cytokines causes hypovelemic shock, fever, a skin rash with defoliation, diarrhea and vomiting.

Question 29

What two bacteria are a common and increasingly dangerous cause of nosocomial and iatrogenic infections

Answer 29

S. Aureus, S. Epidermidis

Question 30

What is a main way in which antibiotic resistant Staph is proliferated?

Answer 30

They are usually encoded by plasmids that are readily shared between species and strains, even between enteric bacteria and Staph.

Question 31

Difference between nosocomial infection and iatrogenic infection

Answer 31

Nosocomial: Hospital acquired Iatrogenic: Doctor acquired