Lecture 3 Part 1: Staphylococci

Question 1

What is the Gram stain and catalase test result for Staphylococcus aureus?

Answer 1

Gram-(+), catalase-(+)

Question 2

How does Staphylococcus aureus grow?

Answer 2

In clusters, with no flagella.

Question 3

Does Staphylococcus aureus form spores?

Answer 3

No, but it can survive in harsh conditions.

Question 4

What environmental conditions can Staphylococcus aureus tolerate?

Answer 4

Facultative anaerobe, high salt, and a wide temperature range.

Question 5

Where is Staphylococcus aureus commonly found in the human body?

Answer 5

On skin and mucosal surfaces.

Question 6

How is Staphylococcus aureus transmitted?

Answer 6

By direct contact or exposure to fomites (contaminated objects).

Question 7

Which antibiotic-resistant strains of Staphylococcus aureus are particularly concerning?

Answer 7

MRSA (Methicillin-resistant S. aureus) and Vancomycin-resistant strains.

Question 8

What type of infections does Staphylococcus aureus cause?

Answer 8

Skin infections (boils) and systemic infections that can be deadly.

Question 9

What are the 4 structural components for Staphylococcus aureus?

Answer 9

1. Capsule and slime layer (11 serotypes)
2. Peptidoglycan (highly cross-linked) with Teichoic acid
3. Surface protein A (SpA)
4. Clfs – clumping factor

Question 10

What is function of Surface Protein A? (SpA)

Answer 10

• bind Fc region of Igs
• stimulate TNFα secretion
• activate B cells

Question 11

What is the function of Staphylococcus aureus Clumping Factors (Clfs)?

Answer 11

bind fibrinogen & FnBPs (fibronectin binding-proteins)

Question 12

coagulase

Answer 12

Converts fibrinogen to fibrin

Question 13

hyaluronidase

Answer 13

it breaks down hyaluronic acid

Question 14

fibrinolysin

Answer 14

It dissolves fibrin clots

Question 15

lipases

Answer 15

hydrolyze lipids

Question 16

nucleases

Answer 16

digests DNA

Question 17

What is the function of Staphylococcus aureus cytotoxins (α, β, δ, γ)?
cytotoxins are toxins that can damage or kill cells

Answer 17

They are cytolytic (break down) for erythrocytes (red blood cells), keratinocytes (, and fibroblasts.

Question 18

Which cytolitc toxin is most important for Staphylococcus aureus and what does it do?

Answer 18

α-toxin. A pore-forming cytotoxin that lyses cells (excluding neutrophils)

Question 19

What does Panton-Valentine Leukocidin (PVL) target?

PVL is another pore forming toxin

Answer 19

neutrophils and platelets

Question 20

How many exfoliative toxins does Staphylococcus aureus produce?

Answer 20

TWO

Question 21

What is the mechanism of exfoliative toxins?

Answer 21

They are serine proteases that disrupt the stratum granulosum of the skin

Question 22

What do do superantigens (SAgs) bind to ?

Answer 22

They bind to T cells and MHC II (causing excessive immune activation)

Question 23

What is the function of enterotoxins (A-R) in Staphylococcus aureus?

Answer 23

They stimulate gastrointestinal activity, leading to vomiting and food poisoning.

Question 24

What is the major effect of Toxic Shock Syndrome Toxin-1 (TSST-1)?

Answer 24

It causes massive cytokine release, leading to leakage & destruction of endothelial cells

Question 25

What are the three major toxin-mediated diseases caused by Staphylococcus aureus?

Answer 25

1. Scalded skin syndrome 2. food poisoning 3. toxic shock syndrome

Question 26

What toxin is responsible for Staphylococcal Scalded Skin Syndrome (SSSS)?

Answer 26

Exfoliative toxins.

Question 27

What is the primary symptom of Staphylococcus aureus food poisoning?

Answer 27

Vomiting due to enterotoxins (A-R).

Question 28

What causes Toxic Shock Syndrome (TSS) in Staphylococcus aureus infections?

Answer 28

Toxic Shock Syndrome Toxin-1 (TSST-1), leading to systemic cytokine release.

Question 29

Name the 5 Cutaneous infections (pyogenic – pus forming, abscesses) caused by Staphylococcus aureus

Answer 29

1. Impetigo: Red sores that rupture, ooze, and form a yellow-brown crust. 2. Folliculitis: Inflammation of hair follicles 3. Furuncles: boils 4. Carbuncles: Clusters of boils 5. Wound infections just know the names I put the definitions as background info

Question 30

Name 4 of the systemic infections caused by Staphylococcus aureus.

Answer 30

1. Bacteremia **2. Endocarditis** **3. Pneumonia** 4. Septic arthritis (usually large joints)

Question 31

What condition occurs when Staphylococcus aureus spreads into the bloodstream?

Answer 31

Bacteremia

Question 32

What serious heart condition can Staphylococcus aureus cause?

Answer 32

Endocarditis

Question 33

what is Coagulase-negative Staphylococci?

Answer 33

These are a group of Staphylococcus species that do not produce the enzyme coagulase. This group includes all Staphylococci except Staphylococcus aureus (S. aureus)

Question 34

TRUE/FALSE Coagulase-negative staphylococci include all Staphylococcus species except S. aureus.

Answer 34

TRUE

Question 35

TRUE/FALSE Coagulase-negative staphylococci are incapable of causing wound infections

Answer 35

FALSE Coagulase-negative staphylococci can cause wound infections

Question 36

Staphylococcus lugdunensis is a common cause of endocarditis.

Answer 36

TRUE

Question 37

Coagulase-negative staphylococci do not cause infections related to medical devices.

Answer 37

FALSE Coagulase-negative staphylococci are a major causes of catheter and shunt infections.

Question 38

Coagulase-negative staphylococci can infect prosthetic joints.

Answer 38

TRUE

Question 39

Staphylococcus saprophyticus is a common cause of urinary tract infections (UTIs).

Answer 39

TRUE

Question 40

What are the four major classes of antibiotics used against Staphylococcus aureus?

Answer 40

1.Beta-lactams 2.macrolides 3. fluoroquinolones 4. vancomycin.

Question 41

What enzyme does Staphylococcus aureus produce to inactivate beta-lactam antibiotics?

Answer 41

Penicillinase, which opens the β-lactam ring

Question 42

What are altered peptidoglycan transpeptidases (PBP 2a), and how do they contribute to resistance?

Answer 42

PBP 2a, also known as penicillin-binding proteins (PBPs), prevent β-lactam antibiotics from binding

Question 43

What is another name for peptidoglycan transpeptidases in bacteria?

Answer 43

Penicillin-binding proteins (PBPs).

Question 44

How does Staphylococcus aureus acquire resistance to beta-lactams?

Answer 44

By acquiring resistance genes encoding altered PBPs.

Question 45

What modification allows Vancomycin-resistant Staphylococcus aureus (VRSA) to resist vancomycin?

Answer 45

Alteration of lipid II