Changing epidemiology of methicillin-resistant Staphylococcus aureus in the Veterans Affairs Healthcare System, 2002–2009

The epidemiology of infections caused by methicillin-resistant Staphylococcus aureus (MRSA) is changing. Temporal trends and differences between healthcare settings must be described in order to better predict future risk factors associated with this dangerous bacterial infection. A national MRSA-infected cohort was identified from 2002 to 2009 in the Veterans Affairs Healthcare System of the United States: hospital (HOS), long-term care (LTC), and outpatient (OPT). We analyzed within-setting time trends using generalized linear mixed models and between-setting differences with χ2 and Wilcoxon rank-sum tests. The incidence of S. aureus, methicillin-susceptible S. aureus (MSSA), and MRSA infections increased significantly over time in all three settings based on modeled annual percentage changes (P < 0.001). MRSA incidence rates rose by 14, 10, and 37% per year in the HOS, LTC, and OPT settings, respectively. Among 56,345 MRSA-infected patients, the comorbidity burden was highest among LTC inpatients (n = 4,427) and lowest among outpatients (n = 7,250), with an average absolute difference in specific comorbidities of +2 and −7%, respectively, compared to HOS inpatients (n = 44,668). Over time, there was a significant (P ≤ 0.02) decrease in previous inpatient admissions and surgeries (all settings); diabetes with complications and surgical site infections (HOS, OPT); and median length of stay and inpatient mortality (HOS, LTC). Alternatively, obesity, chronic renal disease, and depression were more common between 2002 and 2009 (P ≤ 0.02). Over the past 8 years, we observed significant changes in the epidemiology of MRSA infections, including decreases in traditional MRSA risk factors, improvements in clinical outcomes, and increases in other patient characteristics that may affect risk.

ABSTRACT 23 Purpose 24 The epidemiology of infections caused by methicillin-resistant Staphylococcus aureus (MRSA) 25 is changing. Temporal trends and differences between healthcare settings must be described to 26 better predict future risk factors associated with this dangerous bacterial infection. 27 28

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A national MRSA-infected cohort was identified from 2002 through 2009 in the Veterans Affairs 30 Healthcare System of the United States: hospital (HOS), long-term care (LTC), and outpatient 31 (OPT). We analyzed within-setting time trends using generalized linear mixed models and 32 between-setting differences with χ 2 and Wilcoxon rank-sum tests.

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Over the past eight years, we observed significant changes in the epidemiology of MRSA 48 infections, including decreases in traditional MRSA risk factors, improvements in clinical 49 outcomes, and increases in other patient characteristics that may affect risk.

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We therefore sought to describe the underlying patient populations infected with MRSA from 61 diverse healthcare settings of a single source population. Our objectives were to quantify        decade among children and adults in the U.S. and Canada [6,10,16]. Unlike the diverse 9 healthcare settings we evaluated, these other studies were restricted to a single clinical setting, 161 specifically hospitals [6,10,16]. broadening infection control awareness through education [17,18].

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As expected, MRSA-infected long-term care inpatients had a higher comorbidity burden than 185 hospital inpatients, and those hospitalized were in poorer health than outpatients. In quantifying 186 differences between healthcare settings, we found most comorbidities differed by several 187 percentage points comparing hospitalized and long-term care inpatients, although this difference 188 was more pronounced between outpatients and hospital inpatients. In regards to temporal trends among patients infected with MRSA, we observed significant 191 declines in previously established MRSA risk factors, including diabetes with complications [19-192 21], previous hospitalization [7, 20,21], previous surgery [23], and dialysis [17,22,23]. Also  A considerable limitation in our study and several others [10,25,26], is the use of diagnosis 202 codes to identify MRSA infections. Due to the lack of microbiology research databases in U.S.

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healthcare systems, we are limited to diagnosis codes extracted from administrative data and 204 electronic medical records [10,13,25,26]. Until health informatics advancements are made to  [10,27,28]. It is important to note that coding accuracy in VA databases is 214 reportedly higher than other healthcare systems [29,30]. Further, sensitivity has been found to 215 increase with greater numbers of available diagnosis code entries, which is relatively high in the    funding, advisory board, speakers bureau, and/or consultancy.