Staphylococcus aureus is a gram-positive bacterium found in the skin and mucous membranes. Staph infections range from pimples, impetigo, boils, cellulitis folliculitis, carbuncles, scalded skin syndrome, and abscesses to serious illnesses like pneumonia, meningitis, osteomyelitis, endocarditis, toxic shock syndrome, bactermia, and septicemia. Phase contrast. Magnification: 1000x.