BACKGROUND: The study of hospital methicillin-resistant Staphylococcus aureus (MRSA) epidemiology is complicated by its transmissibility. Our objective was to understand how MRSA importation and transmission influence MRSA nosocomial infections in Veterans Affairs Medical Centers (VAMCs). METHODS: We performed hospital-level analyses of acute-care MRSA admission prevalence, acquisition rates, and incident nosocomial clinical culture (INCC) rates, each a surrogate measure of importation, transmission, and nosocomial infection, respectively. We studied 112 VAMCs from October 2007 through September 2010, after the start of a bundled intervention including active surveillance for MRSA. We analyzed data using generalized linear mixed models. RESULTS: A total of 2.9 million surveillance tests were collected from 1.4 million patient admissions. Overall MRSA admission prevalence was 11.4%, acquisition was 5.2 per 1000 patient-days at risk, and INCC was 1.8 per 1000 patient-days at risk. A 10% increase in a hospital's average admission prevalence was associated with a 9.7% increase in its weekly acquisition rates (P < .001) and a 9.8% increase in its weekly INCC rates (P < .001). Significant decreases were observed in all 3 measures during the study period (P < .001). When INCC rates were stratified by nasal MRSA carriage at admission, a significant downward trend was observed only among those initially negative. CONCLUSIONS: Measured associations between MRSA admission prevalence, acquisition rate, and INCC rate were consistent with the hypothesis that decreased acquisition led to decreased importation, which in turn further abated acquisition. The downward trend in INCC rate specifically among individuals with negative admission surveillance tests suggests that decreasing transmission contributed to lower rates of nosocomial MRSA infection.
BACKGROUND: The study of hospital methicillin-resistant Staphylococcus aureus (MRSA) epidemiology is complicated by its transmissibility. Our objective was to understand how MRSA importation and transmission influence MRSA nosocomial infections in Veterans Affairs Medical Centers (VAMCs). METHODS: We performed hospital-level analyses of acute-care MRSA admission prevalence, acquisition rates, and incident nosocomial clinical culture (INCC) rates, each a surrogate measure of importation, transmission, and nosocomial infection, respectively. We studied 112 VAMCs from October 2007 through September 2010, after the start of a bundled intervention including active surveillance for MRSA. We analyzed data using generalized linear mixed models. RESULTS: A total of 2.9 million surveillance tests were collected from 1.4 million patient admissions. Overall MRSA admission prevalence was 11.4%, acquisition was 5.2 per 1000 patient-days at risk, and INCC was 1.8 per 1000 patient-days at risk. A 10% increase in a hospital's average admission prevalence was associated with a 9.7% increase in its weekly acquisition rates (P < .001) and a 9.8% increase in its weekly INCC rates (P < .001). Significant decreases were observed in all 3 measures during the study period (P < .001). When INCC rates were stratified by nasal MRSA carriage at admission, a significant downward trend was observed only among those initially negative. CONCLUSIONS: Measured associations between MRSA admission prevalence, acquisition rate, and INCC rate were consistent with the hypothesis that decreased acquisition led to decreased importation, which in turn further abated acquisition. The downward trend in INCC rate specifically among individuals with negative admission surveillance tests suggests that decreasing transmission contributed to lower rates of nosocomial MRSA infection.
Authors: Richard E Nelson; Vanessa W Stevens; Karim Khader; Makoto Jones; Matthew H Samore; Martin E Evans; R Douglas Scott; Rachel B Slayton; Marin L Schweizer; Eli L Perencevich; Michael A Rubin Journal: Am J Prev Med Date: 2016-05 Impact factor: 5.043
Authors: R Nair; E N Perencevich; M Goto; D J Livorsi; E Balkenende; E Kiscaden; M L Schweizer Journal: Clin Microbiol Infect Date: 2020-01-30 Impact factor: 8.067
Authors: Sanchita Das; Maureen Harazin; Marc Oliver Wright; Irene Dusich; Ari Robicsek; Lance R Peterson Journal: Open Forum Infect Dis Date: 2014-08-19 Impact factor: 3.835
Authors: Karim Khader; Alun Thomas; W Charles Huskins; Molly Leecaster; Yue Zhang; Tom Greene; Andrew Redd; Matthew H Samore Journal: Open Forum Infect Dis Date: 2017-02-10 Impact factor: 3.835
Authors: Athena P Kourtis; Kelly Hatfield; James Baggs; Yi Mu; Isaac See; Erin Epson; Joelle Nadle; Marion A Kainer; Ghinwa Dumyati; Susan Petit; Susan M Ray; David Ham; Catherine Capers; Heather Ewing; Nicole Coffin; L Clifford McDonald; John Jernigan; Denise Cardo Journal: MMWR Morb Mortal Wkly Rep Date: 2019-03-08 Impact factor: 17.586