Staphylococcus Aureus Flashcards
What type of bacteria are Staphylococcus Aureus?
Gram-Positive that are present in normal microbiota in the nose of approx. 30% of human population. They can form biofilms.
There are 31 different species of Staphylococcus bacteria, most of them are harmless. 3 of them are clinically relevant in terms of infections, what are these 3 species.
S. aureus (Most pathogenic), S. epidermidis and S. saphrophyticus (cause UTIs in sexually active females).
What are the 6 examples of serious infections that Staphylococcus aureus can cause?
Bacteraemia (blood-associated infection), Pneumonia (lung), Osteomyelitis (infection of the bone), Meningitis, Acute endocarditis (heart-valve infection), Toxic Shock Syndrome.
What are the two main classes of virulence factors in Staphylococcus aureus based on the stage of growth?
In the exponential phase, SA produces surface proteins for adhesion and immune evasion. In the stationary phase, SA produces toxins to acquire nutrients.
What are the functions of coagulase and Protein A produced by Staphylococcus aureus in the exponential phase?
Coagulase stops clotting, and Protein A breaks down immunoglobulins to evade the immune system.
Which binding proteins does Staphylococcus aureus produce during the exponential phase for adhesion and colonisation?
Fibronectin-binding protein and Fibrinogen-binding protein (clumping factor).
Why does Staphylococcus aureus produce toxins in the stationary phase?
To acquire nutrients when resources become limited.
What is TSST-1, and how does it function?
Toxic Shock Syndrome Toxin-1 (TSST-1) is a superantigen exotoxin that upregulates the inflammatory response, bypassing the need for an antigen in signal transduction. This inflammation leads to cell lysis, releasing nutrients.
What type of toxins are α-toxin and Δ-toxin and what do they do?
α-toxin and Δ-toxin are a pore-forming toxins that disrupt cell membranes, leading to cell lysis.
What is the function of β-toxin in Staphylococcus aureus?
β-toxin is a sphingomyelinase, which degrades sphingomyelin in cell membranes, leading to cell damage.
What is the role of γ-toxin in Staphylococcus aureus infections?
γ-toxin is a leukocidin, meaning it specifically lyses leukocytes (white blood cells).
How do Exfoliative Toxin A and Exfoliative Toxin B affect the skin?
They are serine proteases that specifically target desmogleins, crucial adhesion proteins in the epidermis. This leads to loss of cell-to-cell adhesion, causing widespread blistering.
What is the function of Panton-Valentine Leukocidin (PVL) toxin?
PVL toxin is a pore-forming toxin that targets neutrophils, causing cell lysis and the release of cytokines and proteolytic enzymes, worsening tissue damage. Activated platelets stick to dead neutrophils, forming thrombosis, which may lead to necrosis.
