Staphylococcus aureus bacteria. Coloured scanning electron micrograph (SEM) of Staphylococcus aureus bacteria. These Gram-positive cocci (spherical bacteria) are found in humans and animals. They are found on the skin and the mucous membranes of the nose, throat and other regions. These bacteria are usually harmless, but infection occurs on broken skin or within a blocked sweat or sebaceous gland, resulting in boils, pustules and abscesses. They can also cause food poisoning, producing toxins that induce vomiting. Certain strains of S. aureus induce the potentially fatal toxic shock syndrome (TSS). Magnification: x11,800 at 5x7cm size. x20,000 at 4x5 inch size.