Methods
In this investigation, three data sources were used to identify health-care exposures for CDIs, determine the proportion of CDIs occurring outside hospital settings, and assess whether prevention programs can effectively reduce CDIs. CDC's Emerging Infections Program conducted active, population-based surveillance for CDIs from eight diverse geographic areas in 2010.[5] Program surveillance coordinators received laboratory reports of positive stool C. difficile tests from residents of catchment areas. Cases were defined by a positive C. difficile test in a person without a positive test during the previous 8 weeks (repeat positive tests during this period suggest recurrence).[6] Medical records were reviewed to confirm the presence of symptoms consistent with CDI and to record all health-care exposures during the 12 weeks preceding specimen collection (i.e., minimum duration of antibiotic-induced susceptibility to CDI). CDIs were classified by the patient's location at the time of stool specimen collection and divided into three groups: 1) hospital-onset CDI, occurring in a hospitalized patient with a positive stool specimen collected more than 3 days after admission; 2) nursing home–onset CDI, occurring in a nursing home resident with a positive stool specimen collected at any time during their stay; and 3) community-onset CDI, occurring in an outpatient or an inpatient of any health-care facility with a positive stool specimen collected within 3 days (the median incubation period of C. difficile) after admission. Community-onset CDI cases were subcategorized based on previous health-care exposures during the 12 weeks preceding specimen collection; previous inpatient exposures took precedence over outpatient exposures when classifying cases.
A second data source was the National Healthcare Safety Network (NHSN) Multidrug-Resistant Organism and Clostridium difficile Infection module for laboratory-identified (LabID)-CDI events, which became available in March 2009.[7] Incident LabID-CDI events in NHSN are based on positive C. difficile test results from hospital patients who did not have a previous positive test result reported within that facility during the preceding 8 weeks. LabID-CDI events present on admission were defined by a positive stool specimen collected within the first 3 days of admission; a subset was delineated further if patients were discharged from the reporting hospital in the preceding 4 weeks, during which time previous hospitalization is most likely to influence the risk for CDI.[6,7] Rates of hospital-onset CDI cases were calculated per 10,000 patient-days.
The third set of data included early results from three state-led programs (Illinois, Massachusetts, and New York) similar to other programs in which hospitals collaborated with one another to prevent health-care–associated infections[8] (in this case, hospital-onset CDIs). The three programs included a total of 71 hospitals focused on preventing CDIs during three different periods ranging from 19 to 22 months.* Although the systems for data collection and behavioral change strategies varied among programs, all three used CDC surveillance definitions[6] and focused primarily on infection control interventions to prevent transmission of C. difficile; the Massachusetts program did include antibiotic stewardship as a minor component. Using a negative binomial model, rates of hospital-onset CDI from hospitals participating in the three programs were compared between two same-calendar-month, 8-month periods (to control for seasonal variation in rates), one earlier and the other later in the conduct of each program.
Morbidity and Mortality Weekly Report. 2012;61(9):157-162. © 2012 Centers for Disease Control and Prevention (CDC)
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