Clostridium difficile infection (CDI) surveillance

Overview
Clostridium difficile infection surveillance is a collaborative project of the Centers for Disease Control and Prevention (CDC) and seven state Emerging Infection Programs (EIP). This project is part of CDC’s Healthcare Associated Infections-Community Interface (HAIC). Investigators in the surveillance system include personnel from the Division of Healthcare Quality Promotion (DHQP, NCEZID), the Division of Foodborne, Waterborne and Environmental Diseases (DFWED, NCEZID), EIP-funded university-affiliated and state health department personnel, and select reference laboratories.

Project Objectives
• Determine the population-based incidence of community- and healthcare-associated CDI among participating EIP sites.
• Characterize C. difficile strains that are responsible for CDI in San Francisco County with a focus on strains from community-associated cases.
• Describe the epidemiology of community- and healthcare-associated CDI and generate hypotheses for future research activities using EIP CDI surveillance infrastructure.

Case definition: A case of CDI is defined as a stool positive for C. difficile toxin by either enzyme immunoassay or molecular assay (e.g. PCR) on an incident stool specimen from a resident of San Francisco County. Cases that have a positive stool specimen for C. difficile toxin greater than eight weeks after the last positive specimen will be considered as an incident case of CDI. Therefore, for surveillance purposes an individual may be classified and captured as a new incident case if eight consecutive weeks has elapsed since their last positive test for C.difficile.

Initial case classification: A CDI case will be classified as healthcare facility-onset (HCFO) if the initial specimen that yielded the positive C. difficile toxin result was collected greater than three calendar days after admission to a healthcare facility (e.g. acute care hospital, long-term acute care hospital, long-term care facility). A CDI case will be classified as community-onset (CO) if the initial specimen that yielded the positive C. difficile toxin result was collected in an outpatient setting or within the first three calendar days of a healthcare facility admission.

Secondary case classification: Among CO cases, cases will be further classified either as community-onset healthcare facility-associated (CO-HCFA) or community-associated (CA).

Recurrent episodes: CDI cases that have a positive stool specimen for C. difficile between 2 to 8 weeks of the last positive specimen will be considered as a recurrent episode of CDI.

Duplicate episodes: CDI cases that have a positive stool specimen for C.difficile less than 2 weeks of the last positive specimen will be considered as a duplicate episode.

Active Surveillance
Stool specimens positive for C. difficile toxin, by assay or PCR, are identified from all healthcare facility-based and outpatient diagnostic clinical laboratories serving San Francisco County residents.

Stool Testing
Remnant stool specimens from a subset of cases testing positive for C. difficile toxin will be submitted to reference laboratories for culturing, and isolates will be sent to CDC for confirmation and molecular typing.

For more information on the CDI project, please visit the CDC CDI website:
Coming soon

More CDI information
CDC CDI: http://www.cdc.gov/HAI/organisms/cdiff/Cdiff_infect.html
CA Dept of Public Health: http://www.cdph.ca.gov/programs/hai/Pages/ClostridiumDifficile(CDiff).aspx

Questions about the project:
Joelle Nadle, MPH
HAI and MRSA Project Coordinator
California Emerging Infections Program
360 22nd Street, Suite 750
Oakland, CA 94612
Phone 510-451-2248
Fax 510-451-3210

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