Isolation and characterization of micrococci from human skin, including two new species: Micrococcus lylae and Micrococcus kristinae

The medical literature has, for many years, made reference to a group of aerobic, saprophytic bacteria known as Sarcina that have been commonly isolated from human skin. Recent taxonomic studies have indicated that most aerobic strains maintained in various culture collections under the name of Sarcina belong to the species M. luteus or M. varians. Not until 1973 was a comprehensive report on the taxonomic status of this species made available. Earlier reports were somewhat confusing, and, with the lack of a clearly defined species status, cutaneous isolates may have been simply placed in Baird Parker's Micrococcus subgroups together with other species. Micrococci were commonly isolated from the skins of people living in various regions of the United States. Not all micrococci isolated in this investigation could be identified with the currently recognized species of Micrococcus, viz., M. luteus, M. varians, or M. roseus, and these micrococci therefore became the subject of further taxonomic study. As a result of this study, two new species are proposed: M. lylae and M. kristinae. The type strains of these species are ATCC 27566 and ATCC 27570, respectively. Numerous strains were isolated that were similar to M. sedentarius or M. nishinomiyaensis, species that were previously represented by only single strains. (ZoBell's strain 541 [ATCC 14392; CCM 314] is designated herein as the type strain of M. sedentarius.) A few micrococci were left unclassified. A variety of morphological, physiological, biochemical, and genetic characters were examined for their use as taxonomic criteria, and key characters, many of which can be determined by simple laboratory procedures, were selected for species differentiation. The more sophisticated studies of aliphatic hydrocarbons and cell wall peptidoglycans were also very useful in the taxonomy on the micrococci. The predominant micrococci found on human skin were M. luteus and M. varians.