156. Changes in Diagnostic Methods Used by Clinical Laboratories to Detect Shiga Toxin-Producing Escherichia coli (STEC) Infections—FoodNet, 2007–2012
Session: Poster Abstract Session: Diagnostic Microbiology
Thursday, October 18, 2012
Room: SDCC Poster Hall F-H
  • ModyR_IDSA_2012_FINAL.pdf (292.9 kB)
  • Background: Although STEC O157 remains the type of STEC most associated with severe illness and outbreaks in the United States, some non-O157 STEC can be equally virulent. Guidelines published in 2009 recommend that all stool samples submitted from patients with acute community acquired diarrhea be cultured for STEC O157 on selective and differential media and simultaneously assayed for non-O157 STEC with a test that detects Shiga toxins or Shiga toxin genes. We describe STEC diagnostic practices used by clinical laboratories in 2012 and compare how practices have changed since 2007.     

    Methods: FoodNet is a population-based surveillance network of 10 sites covering 15% of the US population. FoodNet published a description of STEC detection practices used by clinical laboratories serving the surveillance area in 2007. During January–March 2012, FoodNet conducted a follow-up survey of all clinical laboratories in FoodNet. Changes in practice were assessed using a chi-square test. Analyses were limited to laboratories that performed on-site STEC testing.       

    Results: In 2012, 61% of 647 laboratories surveyed performed on-site STEC testing, similar to that reported in 2007 (64% of 664). We observed a decrease in laboratories that perform any STEC O157 culturing (93% of laboratories in 2007; 84% in 2012) and an increase in laboratories that perform any Shiga toxin testing (11% in 2007; 53% in 2012).  We observed no change in laboratories that culture all diarrheal stool samples for STEC O157 (66% in both years) and observed marked increases in laboratories that test all samples for Shiga toxin (7% in 2007; 41% in 2012) or both test for Shiga toxin and culture for STEC O157 (2% in 2007; 22% in 2012) on all samples. All changes were significant (P <0.0001). Changes varied by site. 

    Conclusion: We observed an 11-fold increase (2% to 22%) in clinical laboratories that follow the recommended approach to STEC diagnosis, a change driven by increased use of tests that detect Shiga toxin. The decline in overall use of STEC O157 culture and lack of increase in the practice of STEC O157 culture of all diarrheal stools is detrimental, to both individual patients with STEC O157 infection and to public health, because culture remains the fastest and most reliable method to detect STEC O157 infection and outbreaks.

    Rajal K. Mody, MD, MPH1, Carlota Medus, PhD, MPH2, Jennifer Huang, MPH1,3, Mary Patrick, MPH1, Alicia Cronquist, MPH4, Kathryn Wymore, MPH5, Sharon Hurd, MPH6, Nancy L. Spina, MPH7, Olga Henao, PhD, MPH1 and Patricia M. Griffin, MD1, (1)Division of Foodborne, Waterborne, and Environmental Diseases, CDC, Atlanta, GA, (2)Minnesota Dept Health, St. Paul, MN, (3)Oak Ridge Institute for Science and Education, Atlanta, GA, (4)Colorado Dept of Health and Env, Denver, CO, (5)California Emerging Infections Program, Oakland, CA, (6)Connecticut FoodNet Program, Yale University, New Haven, CT, (7)Emerging Infections Program, New York State Department of Health, Albany, NY


    R. K. Mody, None

    C. Medus, None

    J. Huang, None

    M. Patrick, None

    A. Cronquist, None

    K. Wymore, None

    S. Hurd, None

    N. L. Spina, None

    O. Henao, None

    P. M. Griffin, None

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