Straphylococcus

Question 1

Explain the resistance of staph to the following:

1. Heat
2. Boiling
3. Pasteurization
4. Disinfectants
5. Soap
6. Phenol
7. Iodine

Answer 1

1. Heat = somewhat resistant
2. Boiling = killed quickly
3. Pasteurization = killed
4. Disinfectants = somewhat resistant
5. Soap = resistant
6. Phenol = killed
7. Iodine = killed

Question 2

What is the natural habitat of staph?

Answer 2

Skin flora of most mammals and some avians

30% of humans are nasal carriers

Also present in oral cavity

Question 3

Peptidoglycan is what percentage of the cell wall of S. aureus?

Answer 3

50-60%

Question 4

1. Teichoic acid in S. aureus is of the _____ type.
2. Teichoic acid of S. epidermidis is of the ____ type.

Answer 4

1. Teichoic acid in S. aureus is of the polyribitol type.
2. Teichoic acid in S. epidermidis is of the polyglycerol type.

Question 5

True or False:

1. Antibodies agaisnt the teichoic acid component are found in low levels in normal humans.
2. The level of antibody increases durin more severe infetions with S. aureus.

Answer 5

1. TRUE
2. TRUE

Question 6

S. aureus

Teichoic acid is released from the cell and combines with antibodies present. What is this responsible for?

Answer 6

Teichoic acid is released from the cell and combines with antibodies present. This is responsible for the consumption of complement components up through C5.

(Anti-complement)

Question 7

S. aureus:

What are the 4 biological effects of Protein A?

Answer 7

1. Anti-complement
2. Anti-phagocytic
3. Chemotractic
4. Platelet injury

Question 8

S. aureus:

Protein A is a major component of the cell wall. In which other species of staphylococcus can this component be found?

Answer 8

S. pseudintermedius

Question 9

S. aureus:

Protein A serves as a receptor for what?

Answer 9

Serves as a receptor for the Fc fragment of the immunoglobulin molecule

Question 10

S. aureus:

Which component is responsible for the breakdown of bactericidal fatty acids on the skin, allowing the organism to colonize tissue?

Answer 10

Lipases

Question 11

S. aureus alpha hemolysin:

What is the mechanism of action?

Answer 11

Heptamer forming transmembrane channels (pores)

(Causes membrane damage to a number of mammalian cell types. Produces a lot of tissue necrosis)

Question 12

S. aureus beta hemolysin:

What is the mechanism of action?

Answer 12

Phospholipase C activity digests cells:

Hot-cold lysis (collapse of erythrocyte cell membrane at less than 10 degrees celcius)

Question 13

What type of properties does the gamma hemolysin have in S. aureus?

Answer 13

1. Pro-inflammatory
2. Hemolytic

Question 14

What type of special activity does the delta hemolysin have in S. aureus?

Answer 14

Detergent-like

Question 15

What 2 properties does the delta hemolysin have in S. aureus?

Answer 15

1. Lethal
2. Dermonecrotic

Question 16

What is the major source of variability in hemolytic activity?

Answer 16

Beta hemolysin

Question 17

What does leukocidin work against?

Answer 17

PMNs

Macrophages

Question 18

How does leukocidin kill PMNs and macrophages?

Answer 18

By assembling a ring structure on cell membranes and creating a pore

Question 19

1. What is staphylokinase?
2. What is its function?

Answer 19

1. Fibrinolysin
2. Breaks down a fibrin barrier and allows the spread of the organism

Question 20

S. aureus:

What is the most important indicator of clinical significance?

Answer 20

Coagulase

(Highly correlated with pathogenicity)

Question 21

Staphylocoagulase + _____ –> staphylothrombin

Staphylothrombin –> _____ –> fibrin

Answer 21

Staphylocoagulase + prothrombin –> staphylothrombin

Staphylothrombin –> fibrinogen –> fibrin

Question 22

1. What is hyaluronidase responsible for?
2. When in an infection is it important?

Answer 22

1. Responsible for the breakdown of hyaluronic acid in tissues
2. Important early in an infection

Question 23

DNase is a nuclease capable of acting on RNA and DNA.

Nucleases are important to bacteria becuase they stimulate what?

Answer 23

Stimulate the formation of abscesses by assisting in liquefaction of pus and obtaining of nutrients

Question 24

What are the 4 superantigens of staphylococcal species?

Answer 24

1. Enterotoxin (A-E, G and H)
2. Staphylococcal food poisoning
3. Toxic shock syndrome toxin - 1
4. Exfoliative toxin (A and B)

Question 25

True or False: 1. Not all enterotoxins are superantigens. 2. Enterotoxins all cause gastrointestinal intoxication resulting in emesis, diarrhea, and enteritis.

Answer 25

1. FALSE - all enterotoxins are superantigens 2. TRUE

Question 26

How heat resistant is the staphylococcal food poisoning?

Answer 26

Withstands boiling for 30 minutes

Question 27

What symptoms are seen after ingestion of staphylococcal food poisoning?

Answer 27

Vomiting Diarrhea Prostration Some fatalities

Question 28

What toxin is resposible for scalded skin syndrome seen in newborn humans?

Answer 28

Exfoliative toxin

Question 29

How does the exfoliative toxin work?

Answer 29

Causes lysis of the intracellular binding material of the epidermis

Question 30

Which superantigens have isolates from severe peracute mastitis in cattle been shown to express?

Answer 30

1. Toxic shock syndrome toxin - 1 2. Staphylococcus enterotoxin C

Question 31

What is most commonly isolated from wounds and abscesses on a horse?

Answer 31

Staphylococcus pseudintermedius

Question 32

What does Staph schleiferi cause in dogs?

Answer 32

Recurrent pyoderma & otitis media

Question 33

True or False: Staph schleiferi tends to recur following a course of antimicrobial therapy.

Answer 33

TRUE

Question 34

What is responsible for the majority of **subclinical** or **mild** mastitis seen in dairy cattle?

Answer 34

Staph epidermidis

Question 35

What is thought to be the most common cause of mastitis in goats?

Answer 35

Coagulase negative staph

Question 36

Which organism is increasingly recognized as a cause of septicemia associated with intravenous catheterization & prosthetic devices?

Answer 36

Staph epidermidis

Question 37

What is the cause of exudative epidermatis in pigs?

Answer 37

Staph hyicus subspecies 1

Question 38

1. Which organism produces 4 different exfoliative toxins? 2. What are they?

Answer 38

1. Staph hyicus subspecies 1 2. A, B, C, D

Question 39

1. Staph hyicus is also frequently related to what 2 abnormalities? 2. Plus, in addition to exudative epidermitis, staph hyicus is also implicated as a cause of what else in pigs?

Answer 39

1. Enlarged ureters & cystic kidneys 2. Septic polyarthritis

Question 40

What are the hemolysis patterns for the following staph species? 1. aureus 2. pseudintermedius 3. hyicus subspecies 1 4. epidermidis 5. schleiferi

Answer 40

1. aureus = DZ 2. pseudintermedius = DZ 3. hyicus subspecies 1 = none 4. epidermidis = none 5. schleiferi = DZ

Question 41

What is the coagulase result for the following staph species? 1. aureus 2. pseudintermedius 3. hyicus subspecies 1 4. epidermidis 5. schleiferi

Answer 41

1. aureus (+) 2. pseudointermedius (+) 3. hyicus subspecies 1 (50/50; +/-) 4. epidermidis (-) 5. schleiferi (-)

Question 42

Explain phage typing:

Answer 42

1. Staph is plated out onto an agar plate 2. Drops of phage lysate representing bacteriophages are dropped on the agar surface 3. Plates are incubated overnight 4. If a bacteriophage infects the staph it will lyse it 5. A clear plaque will result

Question 43

What are the 2 Staph aureus enzymes correlated with pathogenicity?

Answer 43

Coagulase DNase

Question 44

The majority of antimicrobial resistance is due to the transfer of what?

Answer 44

R plasmids

Question 45

Penicillin resistant organisms are resistant due to what type of alteration?

Answer 45

Alteration in the transpeptidasei