Microbes of the Body: Gram-positive Cocci

Question 1

What is the rxn that Catalase catalyzes?

Answer 1

Question 2

What does a positive catalase test look like? What does it mean?

Answer 2

• The formation of bubbles (O2) is evidence of catalase activity.
• Catalase is invariably present in aerobes and is also present in some facultative organisms.

Question 3

List the genera below as catalase (+) or catalase (-)

• Streptococcus
• Staphylococcus
• Enterococcus.

Answer 3

List the genera below as catalase (+) or catalase (-)

• Streptococcus
  
  • (-)
• Staphylococcus
  
  • (+)
• Enterococcus.
  
  • (-)

Question 4

Define the following human blood clotting factors

• fibrinogen
• thrombin
• fibrin

Answer 4

Define the following human blood clotting factors

• fibrinogen
  
  • a small, soluble circulating protein
• thrombin
  
  • an enzyme that is part of the coagulation cascade in human blood
• fibrin
  
  • the resultant insoluble network that can trap blood cells and form blood clots

Question 5

How does Staphylococcus aureus protect itself from destruction by human immune cells?

Answer 5

• S. aureus can use its coagulase enzyme to mimic human thrombin and catalyze the conversion of fibrinogen to fibrin.
• This forms a clot that protects it from destruction by human immune cells.

Question 6

How do hemolysins lyse cells?

Answer 6

• Hemolysins are extracellular enzymes that can be detected by their ability to lyse cells.
• These secreted toxins assemble into ring-shaped, hollow structures that insert into cell membranes and form pores that allow the cellular contents to leak out.

Question 7

Describe the 3 types of hemolytic reactions can be observed on blood agar plates

Answer 7

• Alpha hemolysins
  
  • partially lyse the red blood cells and reduce the hemoglobin to methemoglobin which produces a green zone around the colony.
• Beta hemolysins
  
  • cause complete lysis of the red blood cells and there is a clearing of the hemoglobin around the colony.
• Gamma hemolysis
  
  • a term used to designate no hemolysis or change in the red blood cells.

Question 8

Is the genera Staphylococcus catalase (-)?

Answer 8

No, it is catalase (+).

Question 9

Where do most people carry staphylococci?

Answer 9

Skin

Question 10

Staphylococcus epidermiditis is considered a commensal. What does that term mean?

Answer 10

The little bitch freeloading bacteria benefits from living on our skin and we don’t get shit.

Question 11

S. aureus sometimes can be pathogenic – for example, when introduced into parts of the body different from the skin, where it normally resides.

• What are common diseases that arise from this?

Answer 11

• S. aureus is associated with a wide variety of disease states, including impetigo, toxic shock syndrome and food poisoning.

Question 12

What does MRSA stand for?

Answer 12

methicillin-resistant Staphylococcus aureus

Question 13

Why is MRSA a problem?

Answer 13

• MRSA can be problematic, especially in hospitals, because infections cannot be treated with penicillin, methicillin, or other common drugs.
• MRSA is frequently transferred from non-carriers to carriers in hospitals, and immunocompromised patients are more likely to become ill from MRSA.
• Hospital-acquired infections are called nosocomial infections.

Question 14

Is coagulase a virulence factor?

Answer 14

Yea, bitch

Question 15

True or False

• The staphylococci S. aureus, S. epidermidis**, and S. saprophyticus all look different on a microscope slide, based on size.
• The staphylococci S. aureus, S. epidermidis , and S. saprophyticus all form clusters of cells.

Answer 15

True or False

• The staphylococci S. aureus, S. epidermidis**, and S. saprophyticus all look different on a microscope slide, based on size.
  
  • FALSE: They all look identical, hence biochemical ID tests.
• The staphylococci S. aureus, S. epidermidis , and S. saprophyticus all form clusters of cells.
  
  • True

Question 16

True or False

Summary of characteristics of S. aureus

• Salt tolerant
• Cannot ferment mannitol
• Produces a toxin that performs α-hemolysis on blood agar plates
• Produces coagulase enzyme

Answer 16

True or False

Summary of characteristics of S. aureus

• Salt tolerant
• Cannot ferment mannitol
  
  • False: Ferments mannitol to form acid
• Produces a toxin that performs α-hemolysis on blood agar plates
  
  • False: Produces a toxin that performs β-hemolysis on blood agar plates
• Produces coagulase enzyme

Question 17

True or False

The exotoxin that is responsible for α-hemolysis in S. aureus is called α-toxin.

Answer 17

False

The exotoxin that is responsible for β-hemolysis in S. aureus is called α-toxin.

Question 18

Can S. epidermidis ferment mannitol?

Answer 18

nah

Question 19

Does S. epidermidis produce coagulase?

Answer 19

Nah

Question 20

Does S. epidermidis produce α​-toxin?

Answer 20

Nah

Question 21

Does the genera Streptococcus have halophiles?

Answer 21

nah

Question 22

Where does Streptococci normally live in the body?

Answer 22

Streptococci are normal inhabitants of the human pharynx, mouth, and va jay jay.

Question 23

Does the genus Streptococcus grow on MSA plates?

Answer 23

Nah

Question 24

What are the pathogenic streptococci of medical importance?

Answer 24

S. pyogenes, S.* *agalactiae, and S. pneumoniae**.

Question 25

What diseases arise from pathogenic streptococci?

Answer 25

Diseases include

• pneumonia
• scarlet fever
• rheumatic fever
• meningitis
• endocarditis
• pharyngitis
• erysipelas
• glomerulonephritis

Question 26

What is the common cause of a sore throat?

Answer 26

• Blow Jobs
• Streptococcus pyogenes infection

Question 27

True or False

• Streptococci cause both α-hemolysis and β-hemolysis on sheep’s blood agar plates

Answer 27

truuuuuuu

Question 28

What are “viridans streptococci”? Where is this frequently found in the body?

Answer 28

• Streptococci causing alpha hemolysis (resulting in a greenish zone in sheep’s blood agar)
• These are frequently found in patients with dental caries.
  • Dental caries is the scientific term for tooth decay or cavities.

Question 29

What are Streptococcus toxins that are responsible for β-hemolysis called?

• Describe their types

Answer 29

Streptolysins

• Streptolysin O
  
  • oxygen labile (destroyed by oxygen)
• Streptolysin S
  
  • oxygen stable

Question 30

Are streptolysins virulence factors?

Answer 30

YASSS

Question 31

True or False

Even though they are strong pathogens, S. pyogenes and S. agalactiae cannot cause β-hemolysis.

Answer 31

False: They both cause β-hemolysis.

Question 32

True or False

Enterococcus bacteria are catalase negative and usually facultative.

Answer 32

True

Question 33

Is Enterococcus a halophile?

Answer 33

Yass

Question 34

Can the genus Enterococcus also tolerate bile salts?

Answer 34

The genus Enterococcus also tolerates bile salts, which is to be expected from bacteria native to mammalian guts.

Question 35

What is the Enterococcus species most commonly isolated from human infections?

Answer 35

E. faecalis and E. faecium

Question 36

Enterococci were the first to develop what kind of antibiotic resistance?

Answer 36

Enterococci were the first to develop resistance to vancomycin, the antibiotic that is commonly used to combat penicillin-resistant Gram-positive bacteria.

• Vancomycin-resistant Enterocococcus is called VRE.

Question 37

• ________(Streptococcus/Staphylococcus) is Gram-positive, catalase-positive cocci usually found singly or in clusters.
• ________(Streptococcus/Staphylococcus) is Gram-positive, catalase-negative cocci often found in chains.

Answer 37

• Staphylococcus is Gram-positive, catalase-positive cocci usually found singly or in clusters.
• Streptococcus is Gram-positive, catalase-negative cocci often found in chains.