Micrococcus luteus

Micrococcus luteus is a Gram positive, spherical, saprotrophic bacterium that belongs to the family Micrococcaceae. An obligate aerobe, M. luteus is found in soil, dust, water and air, and as part of the normal flora of the mammalian skin. The bacterium also colonizes the human mouth, mucosae, oropharynx and upper respiratory tract.

Although M. luteus is non-pathogenic and usually regarded as a contaminant, it should be considered as an emerging nosocomial pathogen in immunocompromised patients. M.luteus is resistant to reduced water potential and can tolerate drying and high salt concentrations.

M. luteus is coagulase negative, bacitracin susceptible, and forms bright yellow colonies on nutrient agar. To confirm it is not Staphylococcus aureus, a bacitracin susceptibility test can be performed.

M. luteus has been shown to survive in oligotrophic environments for extended periods of time. Recent work by Greenblat et al. demonstrate that Micrococcus luteus has survived for at least 34,000 to 170,000 years on the basis of 16S rRNA analysis, and possibly much longer.