Bacteria in the genus Staphylococcus are Gram-positive cocci that arrange themselves in grape-like clusters. They are shown here at 1000 X magnification, stained with the Gram stain. A well-known pathogenic Staphylococcus is Staphylococcus aureus, which causes infections such as meningitis, pneumonia, toxic shock syndrome, food poisoning, impetigo, osteomyelitis, and carbuncles. Staphylococcus epidermidis is part of the normal flora of the human skin but can be an opportunistic pathogen in a compromised host. It is not possible to distinguish Staphylococcus aureus from Staphylococcus epidermidis in a Gram stain. Both organisms look like the images shown below.

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