Broad-Range PCR and High throughput DNA Sequencing PCR amplification and sequencing of rRNA genes will follow our previously published protocol (13). In brief, DNA lysates are subjected to PCR with pan-bacterial 16S rDNA rDNA primers, which yields libraries of PCR amplicons representative of all bacteria or fungi in a specimen (14). Triplicate PCR reactions will be performed and amplicons pooled for each sample. Poisoning controls spiked with bacterial (e.g. Bacillus subtilis) genomic DNA will be assayed to detect the presence of PCR inhibitors in template DNA preparations; although not typically a problem with nasal swabs, inhibitory samples will be purified by ethanol precipitation and then resubmitted for PCR. PCR amplicon libraries will be sequenced using the high-throughput Illumina MiSeq personal sequencing platform. which is available through the University of Colorado's Division of Infectious Diseases. This platform can generate 5-20x106 DNA sequences in a single instrument run with mean read lengths ~450 nts. The primers used for broad-range PCR include unique barcoded sequences in order to simultaneously sequence multiple amplicon libraries in a single instrument run (15). We will construct and sequence libraries from 100 specimens (50 persistent MRSA carriers [cases] and 50 non-carriers [controls]) to a depth of >50,000 high-quality sequencing reads per specimen. Our preliminary study indicates that this depth of coverage will represent a complete survey of the nares microbiota for each specimen.