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. 2010 Nov;61(5):372-81.
doi: 10.1016/j.jinf.2010.09.021. Epub 2010 Sep 22.

Association of methicillin-resistant Staphylococcus aureus (MRSA) USA300 genotype with mortality in MRSA bacteremia

Russell R Kempker  1 , Monica M Farley, Janine L Ladson, Sarah Satola, Susan M Ray
Affiliations

Association of methicillin-resistant Staphylococcus aureus (MRSA) USA300 genotype with mortality in MRSA bacteremia

Russell R Kempker et al. J Infect. 2010 Nov.

Abstract

Objectives: To evaluate the association of USA300 genotype with outcomes in persons with MRSA bacteremia and examine the epidemiology of MRSA bacteremia over time.

Methods: Population-based surveillance for MRSA bacteremia was performed in 8-county Atlanta from 2005 to 2008. Cases of MRSA bacteremia were classified as healthcare-associated hospital-onset (HAHO), healthcare-associated community-onset (HACO), or community-associated (CA) disease. A survival analysis was performed on a nested cohort of cases with isolates characterized by pulse field gel electrophoresis (PFGE).

Results: 4344 MRSA bacteremia cases were identified; 2579 (59.4%) HACO, 1144 (26.3%) HAHO; and 601 (13.8%) CA. Overall incidence rates of MRSA bacteremia declined from 33.9/100,000 in 2005-24.8/100,000 in 2008. Rates were highest in persons ≥ 65 years, blacks, males, and persons with AIDS. In multivariate analysis of 1104 cases, USA300 genotype was associated with increased in-hospital mortality (HR 1.63, 95% CI 1.19-2.23). USA300 strains were also associated with increased mortality when compared to USA100 strains (HR 1.79, 95% CI 1.24-2.58).

Conclusions: MRSA bacteremia incidence declined over 4 years but CA disease rates remained stable. Persons with HIV, the elderly, and blacks were disproportionately affected. Bacteremia due to USA300 MRSA strains was associated with increased mortality, suggesting that USA300 strains may be more virulent.

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Conflict of interest statement

Conflict of interest: None of the authors have any commercial or other association that may pose a conflict of interest.

Figures

Figure 1
Figure 1
MRSA bacteremia incidence rates by year and epidemiological classification, Atlanta, GA, 2005–2008. Classifications: Healthcare-associated community-onset (HACO); healthcare-associated hospital-onset (HAHO); community-associated (CA). Overall rate includes all HACO, HAHO, and CA cases plus 20 cases with unknown epidemiological classification.
Figure 2
Figure 2
Distribution of PFGE Types in Nested Cohort (N=1104). Other: USA 800 (2.8%), USA700 (1.1%), CAMRSA9, Brazilian, Group D, USA200, USA400, USA600, USA1000, USA1100 (all <1%).
Figure 3
Figure 3
Cox Adjusted Survival Graphs. A, Comparison of USA300 cases vs. Non-USA300 cases. B, Comparison of USA300 cases vs. USA100 cases.
See this image and copyright information in PMC

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