👉 Staphylococcus aureus, also known as Staph, is a Gram-positive bacterium that belongs to the family of Proteobacteria. It's one of the most common causes of bloodstream infections in humans and animals. The name "staph" comes from its characteristic appearance with white or yellowish-white colonies on a surface and sometimes a greenish-yellow coloration within the cell wall, which gives it the name "staphylococcus".