Original Article

Widespread Emergence of Methicillin Resistance in Community-acquired Staphylococcus aureus Infections in Denver

Authors: Megan J. Clancy, MD, Amy Graepler, MT, Peter E. Breese, MSPH, Connie S. Price, MD, William J. Burman, MD

Abstract

Background: Increasing rates of methicillin resistance among outpatient Staphylococcus aureus infections led us to assess the epidemiology and outcome of a local outbreak.


Methods: A retrospective cohort study of outpatient skin and soft tissue infections due to S aureus in 2003.


Results: From 2002 to mid-2004, the percentage of outpatient S aureus isolates resistant to methicillin increased from 6 to 45%. In multivariate analysis, only male sex and age greater than 18 years were associated with methicillin resistance. Methicillin resistance was common (>15%) among isolates from patients in nearly all subgroups evaluated. Pulsed field gel electrophoresis showed isolates related to USA 300, but methicillin-resistant strains had unusually high rates of quinolone resistance.


Conclusions: A single strain of methicillin-resistant S aureus is responsible for the increase in skin infections in outpatients without traditional risk factors for infection with an antibiotic-resistant strain. In areas with high rates of methicillin-resistant S aureus outpatient infections, we recommend non–β-lactam antibiotics for initial treatment of skin and soft tissue infections.


Key Points


* There is a rapid increase in community-acquired methicillin-resistant Staphylococcus aureus skin and soft tissue infections.


* These infections are widespread in the community, and we were unable to identify an at-risk group.


* These infections did not have worse outcomes than infections from methicillin-susceptible isolates.


* These infections were caused by a single pulsed field type that is responsible for outbreaks in other parts of the country.

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