E. coli and Shiga-toxin Reporting

Indiana Epidemiology Newsletter
October 2007

Lynae Granzow, MPH
Enteric Epidemiologist

The ISDH has recently received questions from local health departments (LHD), laboratories, and health care professionals (HCP) about reporting laboratory results of "shiga toxin". Escherichia coli shiga toxins belong to the same toxin family as that produced by Shigella dysenteriae type 1. Many laboratories are performing shiga-toxin testing by EIA (enzyme immunoassay), since results by EIA can be obtained much faster than culture. If a person develops hemolytic uremic syndrome (HUS), the organism may not be detected in culture, but the EIA will be positive. EIA testing also detects other enterohemorrhagic E. coli (EHEC) types that are not O157 but do produce shiga toxin. 

The LHD will investigate a shiga-toxin positive case as an E. coli case, not a Shigella case. Although the ISDH E. coli investigation form has not yet been updated to reflect this change in laboratory testing, please continue to use the E. coli O157:H7/HUS form (#49689) for reporting all diarrhea-producing E. coli infections and write in “shiga-toxin positive” under “Culture Results”. Since shiga toxins can be found in other organisms, all culture results should be included with the investigation form. The case will be considered a “probable” case of E. coli infection if the only laboratory results available are shiga toxin by EIA.

Health care providers must immediately report any positive shiga-toxin test results and diarrhea-producing E. coli cases to the LHD.  Laboratories must immediately report any shiga-toxin positive results to the ISDH.  Laboratories must also submit E. coli isolates to the ISDH Laboratories. Prompt reporting and submission of isolates to the ISDH are essential in determining if the isolate is part of an outbreak.

For more information on disease reporting, please refer to the Communicable Disease Rule for Physicians, Hospitals, and Laboratories, 410 IAC 1-2.3, October 11, 2000. HCP requirements are included on pages 12-16, and laboratory reporting requirements are included on pages 16-18. Communicable disease reports may be faxed to the ISDH at 317.234.2812. Please note that results received from reference laboratories also need to be sent by the submitting laboratory.

For more information, please see the Centers for Disease Control and Prevention (CDC) case definition for E. coli at http://wwwn.cdc.gov/NNDSS/script/conditionsummary.aspx?CondID=49 and the CDC case statement for shiga-toxin testing at www.nphl.org/documents/ShigaToxinTestingRecommendations.pdf.  You may also contact Lynae Granzow, ISDH Enteric Epidemiologist, at 317.233.7125.