| Summary: | <p>Abstract</p> <p>Background</p> <p>The virulence, antimicrobial resistance, and prevalence of <it>S. aureus </it>underscores the need for up-to-date and extensive insights regarding antimicrobial susceptibility trends. One approach to meet this need is analysis of clinical laboratory – based surveillance data.</p> <p>Methods</p> <p>Data from The Surveillance Network-USA (TSN), an electronic surveillance network that collects microbiology data from 300 clinical microbiology laboratories across the United States, were used as the source for analysis that included prevalence of <it>S. aureus </it>in clinical specimens, MRSA and multi-drug resistance phenotype rates and trends according to patient location, geographic distributions, and specimen source.</p> <p>Results</p> <p><it>S. aureus </it>was the most prevalent species isolated from inpatient specimens (18.7% of all bacterial isolates) and the second most prevalent (14.7%) from outpatient specimens. In March 2005 MRSA rates were 59.2%, 55%, and 47.9% for strains from non-ICU inpatients, ICU, and outpatients, respectively. This trend was noted in all nine US Bureau of Census regions and multi-drug resistance phenotypes (resistance to ≥ 3 non-beta-lactams) was common among both inpatient MRSA (59.9%) and outpatient MRSA (40.8%). Greater than 90% of multi-drug resistant MRSA were susceptible to trimethoprim-sulfamethoxazole, linezolid, and vancomycin.</p> <p>Conclusion</p> <p>Prevalence of MRSA among both inpatient and outpatient specimens continues to increase with multi-drug resistance as a common phenotype. Continued emergence of outpatient MRSA that exhibit multi-drug resistant phenotypes has important implications for developing and evolving outpatient treatment guidelines.</p>
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