Lecture 7 Staphylococcus Flashcards Preview

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Flashcards in Lecture 7 Staphylococcus Deck (32):
0

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

S. aureus
S. epidermidis
S. saprophyticus

1

What is the major location for S. aureus

In the nasal cavity

2

Major location for S. epidermidis?

Dry skin or epithelium

3

Major location for S. saprophyticus

Mucosa, Moist epithelium

4

Which of the three Staph organisms are Coagulase +?

S. aureus

5

4 main characteristics of S. aureus

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.

6

4 characteristics of S. epidermidis

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

7

2 characteristics of S. saprophyticus

1. No Coagulase
2. Urinary tract infections in young women

8

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

S. saprophyticus

9

Does S. aureus have a high carrier rate?

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

10

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

Vancomycin

11

Name the 6 virulence factors on S. aureus

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 +

12

How is catalase a virulence factor for S. aureus

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

13

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

Exfoliative Toxin

14

How do catalytic toxins work?

They lyse most cells, including host defense cells

15

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

1. 'True' Food poisoning
2. Toxic Shock syndrome

16

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

Toxic Shock Syndrome toxin (TSST-1)

17

How does Protein A work?

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

18

How does Coagulase work as a virulence factor

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

19

Difference between secreted coagulase and surface coagulase

-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

20

What leads to an abcess?

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

21

Name 3 specific spreading factors

Staphylokinase
Lipase
Hyaluronidase

22

4 types of local infection caused by S. aureus

Local Skin infections
Deep, localized infections
Acute Endocarditis
Pneumonia

23

Local skin infections may lead to what?

Cellulitis and Bacteremia

24

2 examples of Local skin infection

Abscesses (boils, carbuncles)
Impetigo

25

3 examples of Deep, localized infections

Abscesses of the spleen, liver and kidney
Osteomyelitis
Septic Arthritis

26

Explain Scalded skin syndrome

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

27

Explain 'True' Food poisoning

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

28

What occurs during the Toxic Shock syndrome

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.

29

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

S. Aureus, S. Epidermidis

30

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

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

31

Difference between nosocomial infection and iatrogenic infection

Nosocomial: Hospital acquired
Iatrogenic: Doctor acquired