| Summary: | Most forms of life, including the archaea, bacteria, and eukaryotes synthesize the polyamine putrescine. Although putrescine is widely distributed, several Gram-positive bacteria, including <i>Staphylococcus aureus</i> (<i>S. aureus</i>), appear to be the exceptions. We report here that strains of <i>S. aureus</i> can produce the polyamine putrescine, as well as the derivative <i>N</i>-acetyl-putrescine. Three strains of <i>S. aureus</i> from the American Type Culture Collection (ATCC), one strain listed in the National Center for Biotechnology Information (NCBI) database, whose genomic sequence is well defined, and well as eight strains from <i>S. aureus</i>-induced brain abscesses of individual patients from multiple geographic locations were evaluated. Each strain was grown in complete chemically defined medium (CDM) under stringent conditions, after which the partially purified conditioned medium (CM) was analyzed by mass spectroscopy (MS), and the data were reported as the <i>ratio</i> of experimental results to controls. We confirmed the synthesis of putrescine by <i>S. aureus</i> by using <sup>13</sup>C/<sup>15</sup>N-labeled arginine as a tracer. We found that agmatine, <i>N</i>-acetyl-putrescine, ornithine, citrulline, proline, and NH<sub>3</sub> were all labeled with heavy isotope derived from <sup>13</sup>C/<sup>15</sup>N-labeled arginine. None of the strains examined produced spermine or spermidine, but strains from either ATCC or human brain abscesses produced putrescine and/or its derivative <i>N</i>-acetyl-putrescine.
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