Chief of the Escherichia and Shigella Reference Unit
Division of Foodborne, Waterborne, and Environmental Diseases (DFWED),
National Center for Emerging and Zoonotic Infectious Diseases (NCEZID),
Centers for Disease Control and Prevention (CDC)
1600 Clifton Rd., Atlanta, GA 30329-4027
Approaches to testing and serotyping Escherichia coli at the Centers for Disease Control and Prevention (CDC), Atlanta, GA
Serotyping continues to be a valuable tool for defining the diversity extant within Escherichia coli and identifying its pathogenic clones. Antibody-based methods targeting the O and H surface antigens have been used at CDC for over 65 years to identify and subtype strains of public health concern. Agglutination assays with specific O and H antisera, which serve as the gold standard methods for determining these antigens, are currently performed on all E. coli isolates testing positive for potential virulence genes by PCR. The serotype information generated is currently used in surveillance to help detect clusters, study trends and name patterns within PulseNet, the molecular subtyping network for foodborne bacterial disease surveillance in the United States and other countries. Performing traditional O:H serotyping is resource intensive and will not be sustainable into the future. Implementation of a DNA-based approach for serotyping E. coli developed by scientists in Denmark is in progress and will be validated in parallel with traditional serotyping. This presentation will review the present algorithms for testing and serotyping E. coli at CDC and the planned approach for validating the DNA-based method.