Pyogenic Cocci: Genus Staphylococci

These flashcards cover key concepts related to the genus Staphylococci, focusing on their classification, virulence factors, diseases caused, and diagnostic methods.

What are the two main types of Staphylococci based on coagulase production?

Coagulase positive Staphylococci (e.g., Staphylococcus aureus) and coagulase negative Staphylococci (e.g., Staphylococcus epidermidis, Staphylococcus saprophyticus).

What distinctive feature is used to identify coagulase positive Staphylococcus aureus in the laboratory?

S.aureus is coagulase positive, while other Staphylococcus species are coagulase negative.

Which Staphylococcus species is known for causing food poisoning?

Staphylococcus aureus.

What virulence factor is associated with the ability of S.aureus to evade the immune system?

Protein A, which binds to the Fc portion of IgG and inhibits opsonization.

What is the characteristic arrangement of Staphylococci when viewed under a microscope?

Staphylococci appear in irregular grape-like clusters.

Which biochemical test is primarily used to differentiate Staphylococcus from Streptococcus?

The catalase test; Staphylococci are catalase positive.

What are some common infections caused by Staphylococcus aureus?

Skin infections (like impetigo, carbuncles), pneumonia, toxic shock syndrome, and food poisoning.

What is the key laboratory diagnosis method for Staphylococcus aureus?

Culture on mannitol salt agar, where S.aureus ferments mannitol, turning the medium yellow.

What does MRSA stand for, and why is it significant?

Methicillin-resistant Staphylococcus aureus; it is significant due to its resistance to beta-lactam antibiotics.

What is a common method of Staphylococcus aureus transmission?

Through hands, sneezing, or contact with contaminated food.

What pigment does Staphylococcus aureus produce, and what is its role?

Staphyloxanthin, which gives colonies a golden color and enhances pathogenicity by neutralizing oxidative stress.