Lecture 3 Part 1: Staphylococci Flashcards
What is the Gram stain and catalase test result for Staphylococcus aureus?
Gram-(+), catalase-(+)
How does Staphylococcus aureus grow?
In clusters, with no flagella.
Does Staphylococcus aureus form spores?
No, but it can survive in harsh conditions.
What environmental conditions can Staphylococcus aureus tolerate?
Facultative anaerobe, high salt, and a wide temperature range.
Where is Staphylococcus aureus commonly found in the human body?
On skin and mucosal surfaces.
How is Staphylococcus aureus transmitted?
By direct contact or exposure to fomites (contaminated objects).
Which antibiotic-resistant strains of Staphylococcus aureus are particularly concerning?
MRSA (Methicillin-resistant S. aureus) and Vancomycin-resistant strains.
What type of infections does Staphylococcus aureus cause?
Skin infections (boils) and systemic infections that can be deadly.
What are the 4 structural components for Staphylococcus aureus?
- Capsule and slime layer (11 serotypes)
- Peptidoglycan (highly cross-linked) with Teichoic acid
- Surface protein A (SpA)
- Clfs – clumping factor
What is function of Surface Protein A? (SpA)
- bind Fc region of Igs
- stimulate TNFα secretion
- activate B cells
What is the function of Staphylococcus aureus Clumping Factors (Clfs)?
bind fibrinogen & FnBPs (fibronectin binding-proteins)
coagulase
Converts fibrinogen to fibrin
hyaluronidase
it breaks down hyaluronic acid
fibrinolysin
It dissolves fibrin clots
lipases
hydrolyze lipids
nucleases
digests DNA
What is the function of Staphylococcus aureus cytotoxins (α, β, δ, γ)?
cytotoxins are toxins that can damage or kill cells
They are cytolytic (break down) for erythrocytes (red blood cells), keratinocytes (, and fibroblasts.
Which cytolitc toxin is most important for Staphylococcus aureus and what does it do?
α-toxin. A pore-forming cytotoxin that lyses cells (excluding neutrophils)
What does Panton-Valentine Leukocidin (PVL) target?
PVL is another pore forming toxin
neutrophils and platelets
How many exfoliative toxins does Staphylococcus aureus produce?
TWO
What is the mechanism of exfoliative toxins?
They are serine proteases that disrupt the stratum granulosum of the skin
What do do superantigens (SAgs) bind to ?
They bind to T cells and MHC II (causing excessive immune activation)
What is the function of enterotoxins (A-R) in Staphylococcus aureus?
They stimulate gastrointestinal activity, leading to vomiting and food poisoning.
What is the major effect of Toxic Shock Syndrome Toxin-1 (TSST-1)?
It causes massive cytokine release, leading to leakage & destruction of endothelial cells
What are the three major toxin-mediated diseases caused by Staphylococcus aureus?
- Scalded skin syndrome
- food poisoning
- toxic shock syndrome
What toxin is responsible for Staphylococcal Scalded Skin Syndrome (SSSS)?
Exfoliative toxins.
What is the primary symptom of Staphylococcus aureus food poisoning?
Vomiting due to enterotoxins (A-R).
What causes Toxic Shock Syndrome (TSS) in Staphylococcus aureus infections?
Toxic Shock Syndrome Toxin-1 (TSST-1), leading to systemic cytokine release.
Name the 5 Cutaneous infections (pyogenic – pus forming, abscesses) caused by Staphylococcus aureus
- Impetigo: Red sores that rupture, ooze, and form a yellow-brown crust.
- Folliculitis: Inflammation of hair follicles
- Furuncles: boils
- Carbuncles: Clusters of boils
- Wound infections
just know the names I put the definitions as background info
Name 4 of the systemic infections caused by Staphylococcus aureus.
- Bacteremia
2. Endocarditis
3. Pneumonia - Septic arthritis (usually large joints)
What condition occurs when Staphylococcus aureus spreads into the bloodstream?
Bacteremia
What serious heart condition can Staphylococcus aureus cause?
Endocarditis
what is Coagulase-negative Staphylococci?
These are a group of Staphylococcus species that do not produce the enzyme coagulase. This group includes all Staphylococci except Staphylococcus aureus (S. aureus)
TRUE/FALSE
Coagulase-negative staphylococci include all Staphylococcus species except S. aureus.
TRUE
TRUE/FALSE
Coagulase-negative staphylococci are incapable of causing wound infections
FALSE
Coagulase-negative staphylococci can cause wound infections
Staphylococcus lugdunensis is a common cause of endocarditis.
TRUE
Coagulase-negative staphylococci do not cause infections related to medical devices.
FALSE
Coagulase-negative staphylococci are a major causes of catheter and shunt infections.
Coagulase-negative staphylococci can infect prosthetic joints.
TRUE
Staphylococcus saprophyticus is a common cause of urinary tract infections (UTIs).
TRUE
What are the four major classes of antibiotics used against Staphylococcus aureus?
1.Beta-lactams
2.macrolides
3. fluoroquinolones
4. vancomycin.
What enzyme does Staphylococcus aureus produce to inactivate beta-lactam antibiotics?
Penicillinase, which opens the β-lactam ring
What are altered peptidoglycan transpeptidases (PBP 2a), and how do they contribute to resistance?
PBP 2a, also known as penicillin-binding proteins (PBPs), prevent β-lactam antibiotics from binding
What is another name for peptidoglycan transpeptidases in bacteria?
Penicillin-binding proteins (PBPs).
How does Staphylococcus aureus acquire resistance to beta-lactams?
By acquiring resistance genes encoding altered PBPs.
What modification allows Vancomycin-resistant Staphylococcus aureus (VRSA) to resist vancomycin?
Alteration of lipid II
