Antibiotic Resistance Threats in the United States, 2013 report

Technical Appendix
Methicillin-Resistant Staphylococcus aureus (MRSA)
Methods
National estimates of the number of invasive MRSA healthcareassociated
infections (HAIs) were derived from the Emerging Infection
Program/Active Bacterial Core Surveillance 1 for Invasive MRSA using
data reported for infections occurring during 2011 (http://www.
cdc.gov/abcs/reports-findings/surv-reports.html). During 2011,
4,872 reports of invasive MRSA (isolates of MRSA cultured from a normally sterile site and
identified by a participating clinical laboratory) were received from the 9 participating
program sites (population of 19,393,677). Reports include both healthcare-associated
infections and community-associated infections, but are limited to invasive infections
(approximately 85% are bloodstream infections).
Estimates were made using National Center for Health Statistics bridged-race vintage 2011
post-censal file and U.S. renal data systems, adjusting for race, age, gender, and receipt
of dialysis. Mortality includes all-cause mortality during hospitalization, and estimates
were adjusted in similar fashion as infection estimates. Approximately 18% of cases were
reported without a race value, multiple imputation was used to estimate the missing race
based on the data that are available and the results were summarized. Regarding device
and procedure-associated infections with MRSA, the proportion of facilities reporting
at least one S. aureus HAI reported as MRSA for each HAI type was obtained from CDC’s
National Healthcare Safety Network Antimicrobial Resistance Report 2009–2010. 2 Estimates
were rounded to two significant digits.
References
1 Kallen AJ, Mu Y, Bulens S, Reingold A, Petit S, Gershman K, Ray SM, Harrison LH, Lynfield
R, Dumyati G, Townes JM, Schaffner W, Patel PR, Fridkin SK; Active Bacterial Core
surveillance (ABCs) MRSA Investigators of the Emerging Infections Program. Health
care-associated invasive MRSA infections, 2005–2008. JAMA. 2010
2 Sievert DM, Ricks P, Edwards JR, Schneider A, Patel J, Srinivasan A, Kallen A, Limbago
B, Fridkin S; National Healthcare Safety Network (NHSN) Team and Participating NHSN
Facilities. Antimicrobial-resistant pathogens associated with healthcare-associated
infections: summary of data reported to the National Healthcare Safety Network at the
Centers for Disease Control and Prevention, 2009–2010. Infect Control Hosp Epidemiol.
2013 Jan;34(1):1–14
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