infection control & hospital epidemiology july 2017, vol. 38, no. 7 original article
Attributable Mortality of Healthcare-Associated Infections Due to Multidrug-Resistant Gram-Negative Bacteria and Methicillin-Resistant Staphylococcus Aureus
Richard E. Nelson, PhD;1,2 Rachel B. Slayton, PhD;3 Vanessa W. Stevens, PhD;1,2 Makoto M. Jones, MD;1,2 Karim Khader, PhD;1,2 Michael A. Rubin, MD, PhD;1,2 John A. Jernigan, MD;3 Matthew H. Samore, MD1,2
objective. The purpose of this study was to quantify the effect of multidrug-resistant (MDR) gram-negative bacteria and methicillin- resistant Staphylococcus aureus (MRSA) healthcare-associated infections (HAIs) on mortality following infection, regardless of patient location.
methods. Weconducted a retrospective cohort study of patients with an inpatient admission in the US Department of Veterans Affairs (VA) system between October 1, 2007, and November 30, 2010. We constructed multivariate log-binomial regressions to assess the impact of a positive culture on mortality in the 30- and 90-day periods following the first positive culture, using a propensity-score–matched subsample.
results. Patients identified with positive cultures due toMDRAcinetobacter (n=218),MDRPseudomonas aeruginosa (n=1,026), andMDR Enterobacteriaceae (n=3,498) were propensity-score matched to 14,591 patients without positive cultures due to these organisms. In addition, 3,471 patients with positive cultures due to MRSA were propensity-score matched to 12,499 patients without positive MRSA cultures. Multidrug-resistant gram-negative bacteria were associated with a significantly elevated risk of mortality both for invasive (RR, 2.32; 95% CI, 1.85–2.92) and noninvasive cultures (RR, 1.33; 95% CI, 1.22–1.44) during the 30-day period. Similarly, patients with MRSA HAIs (RR, 2.77; 95% CI, 2.39–3.21) and colonizations (RR, 1.32; 95% CI, 1.22–1.50) had an increased risk of death at 30 days.
conclusions. We found that HAIs due to gram-negative bacteria and MRSA conferred significantly elevated 30- and 90-day risks of mortality. This finding held true both for invasive cultures, which are likely to be true infections, and noninvasive infections, which are possibly colonizations.
Infect Control Hosp Epidemiol 2017;38:848–856
Each year an estimated 720,000 healthcare-associated infec- tions (HAIs) or more occur in US acute-care hospitals.1 More than 30% of HAIs are caused by gram-negative bacteria.2 In addition, gram-negative bacteria are the most common source of nosocomial urinary tract infections and pneumonia.3 Infections with methicillin-resistant Staphylococcus aureus (MRSA), a gram-positive bacterium, are also a source of sub- stantial morbidity and mortality in the United States, and more than 14,000 invasive hospital-onset infections occur annually.4 Infections with these resistant organisms often have limited treatment options. In October 2008, the Centers for Medicare and Medicaid
Services (CMS) implemented a policy of not paying for healthcare-associated adverse events determined to have been “reasonably preventable,” including central line-associated bloodstream infections (CLABSIs) and catheter-associated urinary tract infections (CAUTIs).5 Recent evidence suggests that these efforts have led to a significant decrease in
nosocomial infections of these types.6 To evaluate this and other policies designed to reduce HAIs, it is important to have accurate estimates of the consequences of HAIs, including mortality attributable to the infection. Several existing studies have identified an increased risk of mortality associated with nosocomial infections due to gram-negative bacteria, including a high crude mortality rate for Acinetobacter baumanii ranging from 15% to 55%.7–11 However, these studies have been limited to patients from just 1 or 2 hospitals. The purpose of this study was to estimate the 30- and 90-day mortality risks attributable to HAIs with multidrug-resistant (MDR) gram-negative bacteria, specifically Acinetobacter, Pseudomonas aeruginosa, and Enterobacteriaceae, and an important gram-positive bacteria, MRSA, relative to a control group of hospitalized patients in more than 100 hospitals in the United States. These estimates are important for estimating the deaths that could be prevented with more aggressive interventions to prevent HAIs. This study adds to the existing
Utah School of Medicine, Salt Lake City, Utah; 3. Division of Healthcare Quality Promotion, Centers for Disease Control and Prevention, Atlanta, Georgia. © 2017 by The Society for Healthcare Epidemiology of America. All rights reserved. 0899-823X/2017/3807-0012. DOI: 10.1017/ice.2017.83
Affiliations: 1. Veterans Affairs Salt Lake City Health System IDEAS Center, Salt Lake City, Utah; 2. Department of Internal Medicine, University of Received November 8, 2016; accepted March 1, 2017; electronically published June 1, 2017
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