title: Changing epidemiology of methicillin-resistant Staphylococcus aureus in the Veterans Affairs Healthcare System, 2002-2009.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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 χ(2) and Wilcoxon rank-sum tests.
  
  
  RESULTS
  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).
  
  
  CONCLUSIONS
  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.
authors.affiliation: Infectious Diseases Research Program, Veterans Affairs Medical Center (151), Providence, RI 02908, USA.
authors.forename: A R
authors.initials: AR
authors.lastname: Caffrey
authors.forename: K L
authors.initials: KL
authors.lastname: LaPlante
mesh_terms: D000368:Aged; D016009:Chi-Square Distribution; D015331:Cohort Studies; D015897:Comorbidity; D006787:Hospitals, Veterans; D006801:Humans; D015994:Incidence; D016014:Linear Models; D008134:Long-Term Care; D008297:Male; D016106:Methicillin Resistance; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects / Q000502:physiology*; D008875:Middle Aged; D010045:Outpatients; D012189:Retrospective Studies; D012307:Risk Factors; D013203:Staphylococcal Infections / Q000453:epidemiology*; D018709:Statistics, Nonparametric; D013997:Time Factors; D014481:United States; D058014:Veterans Health