A Population-Based Study of the Incidence and Molecular Epidemiology of Methicillin-Resistant Staphylococcus aureus Disease in San Francisco, 2004-2005.
Liu, Catherine 1,2,a; Graber, Christopher J. 1,2,a,b; Karr, Michael 1,2; Diep, Binh An 1,2; Basuino, Li 1,2; Schwartz, Brian S. 1,2; Enright, Mark C. 9; O'Hanlon, Simon J. 9; Thomas, Jonathon C. 9; Perdreau-Remington, Francoise 1,2; Gordon, Shelley 3; Gunthorpe, Helen 4; Jacobs, Richard 1,5; Jensen, Peter 1,6; Leoung, Gifford 7; Rumack, James S. 8; Chambers, Henry F. 1,2
[Article]
Clinical Infectious Diseases.
46(11):1637-1646, June 1, 2008.
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Background. Methicillin-resistant Staphylococcus aureus (MRSA) infections have become a major public health problem in both the community and hospitals. Few studies have characterized the incidence and clonal composition of disease-causing strains in an entire population. Our objective was to perform a population-based survey of the clinical and molecular epidemiology of MRSA disease in San Francisco, California.
Methods. We prospectively collected 3985 MRSA isolates and associated clinical and demographic information over a 12-month period (2004-2005) at 9 San Francisco-area medical centers. A random sample of 801 isolates was selected for molecular analysis.
Results. The annual incidence of community-onset MRSA disease among San Francisco residents was 316 cases per 100,000 population, compared with 31 cases per 100,000 population for hospital-onset disease. Persons who were aged 35-44 years, were men, and were black had the highest incidence of community-onset disease. The USA300 MRSA clone accounted for 234 cases of community-onset disease and 15 cases of hospital-onset disease per 100,000 population, constituting an estimated 78.5% and 43.4% of all cases of MRSA disease, respectively. Patients with community-onset USA300 MRSA versus non-USA300 MRSA disease were more likely to be male, be of younger age, and have skin and soft-tissue infections. USA300 strains were generally more susceptible to multiple antibiotics, although decreased susceptibility to tetracycline was observed in both community-onset (P=.008) and hospital-onset (P=.03) USA300 compared to non-USA300 strains.
Conclusions. The annual incidence of community-onset MRSA disease in San Francisco is substantial, surpassing that of hospital-onset disease. USA300 is the predominant clone in both the community and hospitals. The dissemination of USA300 from the community into the hospital setting has blurred its distinction as a community-associated pathogen.
(C) Copyright Oxford University Press 2008.
