Staphylococcus aureus

Definition

Staphylococcus aureus is a Gram-positive bacterium commonly found on the skin and in the nasal passages. It can cause a range of infections from minor skin conditions to severe diseases like pneumonia and sepsis.

5 Must Know Facts For Your Next Test

1. Staphylococcus aureus appears as clusters resembling grapes under a microscope due to its cocci shape.
2. It is capable of fermenting mannitol, which can be used as a differentiation test in the lab.
3. Methicillin-resistant Staphylococcus aureus (MRSA) is a significant concern due to its resistance to multiple antibiotics.
4. Virulence factors include protein A, toxins, and enzymes that facilitate tissue invasion and immune evasion.
5. S. aureus can form biofilms on medical devices, making infections difficult to treat.

Review Questions

• What are the primary virulence factors of Staphylococcus aureus?
• How does Staphylococcus aureus appear under Gram staining?
• Why is MRSA particularly challenging to treat?

Related terms

Gram-Positive Bacteria: Bacteria that have thick peptidoglycan cell walls and retain crystal violet stain during Gram staining.

Biofilm:

A community of microorganisms adhering to a surface, protected by an extracellular matrix they secrete.

Antimicrobial Resistance:

The ability of microbes to resist the effects of drugs that once could successfully treat them.