Characterizing the microbial composition of indoor air is
important for a better understanding of disease transmission in
a human population. The natural flora found on human skin
contains abundant levels of Micrococcus and Staphylococcus, which
are shed into the air supply of indoor environments. These
environmentally-derived organisms have been consistently difficult
to classify. Within the micrococci, there is at least one well
known example of a reference strain being mis-categorized [11],
which led to an inaccurate reference standard for Food and Drug
Administration (FDA)-mandated testing. In environmental indoor
air samples, it was found previously that over two thirds of the
environmental isolates were micrococci (Bruker Biotyping),
creating a need for greater accuracy in characterization (6). Characterization
of fermentation characteristics and MALDI TOF profiles
allows that categorization of environmental Micrococcus isolates to
the genus level. Tryptic peptide analysis (e.g., aconitate hydratase)
by MALDI TOF MS profiles provides other criteria for a confirmation
of the species identity for environmental isolates. MALDI TOFeTOF
MSeMS can be used to identify proteins from these peptides. It has
been reported that M. luteus may include more than one biovar,
based on 16S rDNA sequence data [9].