Micrococcus species belong to the family Micrococcaceae. They are present in a variety of ecological niches including human and animal skin, water, dust, soil, indoor and outdoor air. These organisms generally do not infect humans. However, they can cause infection in immune-compromised individuals.
Patients with indwelling central venous catheters treated for pulmonary hypertension have developed infections from Micrococcus spp. as well as other bacteria (e.g., Staphylococcus, Corynebacterium and Pseudomonas).
The presence of these organisms add to the antigenic load from microbes in indoor environments. HIV patients have developed chronic pruritic skin infections from M. Luteus. They are considered opportunistic organisms isolated in recurrent bacteremia, septic shock, arthritis, endocarditis, meningitis, intracranial suppuration and cavitating pneumonia in immune-compromised patients.
Micrococcus are gram positive cocci, ranging from 0.5 to 3.5 µ in diameter. They are usually arranged in tetrads or irregular clusters. There are generally aerobic and the colonies are pigmented. Colonies of M. luteus is yellow and M. roseus are reddish. They can be identified by morphological appearance and because they are oxidase positive.