01/03/2018: Lab Advisory: CDC Investigating Multistate Outbreak of E. coli O157:H7 Infections

Audience: Clinical and public health laboratories

Subject: CDC Investigating Multistate Outbreak of E. coli O157:H7 Infections

Region: CDC, several states, and the U.S. Food and Drug Administration are investigating a multistate outbreak of Shiga toxin-producing E. coli O157:H7 infections (STEC O157:H7) in 13 states. Seventeen illnesses have been reported from California (3), Connecticut (2), Illinois (1), Indiana (1), Michigan (1), Nebraska (1), New Hampshire (2), New York (1), Ohio (1), Pennsylvania (1), Virginia (1), Vermont (1) and Washington (1). Illnesses started on dates from November 15 through December 8, 2017. The Public Health Agency of Canada also is investigating an outbreak of STEC O157:H7 infections in several provinces.

Level: Laboratory Advisory – provides important information for a specific incident or situation; contains recommendations or actionable items to be performed by public health officials, laboratorians, and/or clinicians; may not require immediate action.

Highlights for laboratory professionals:

Action for laboratorians if they suspect food borne illness diagnosis

Diagnostic laboratorians and clinical microbiologists are typically asked to report all cases of certain infections to their local health department and to submit at least the first strain isolated from each patient to the local or state public health laboratory. This process is routine in almost all states for infections with Salmonella, Shigella, Listeria, and E. coli O157:H7, all of which are transmitted commonly by food.

When Shiga toxin is detected by use of an enzyme immunoassay (EIA), but a Shiga toxin-producing E. coli has not been isolated, the diagnostic laboratory should submit the EIA-positive broth to the public health laboratory for isolation and identification. Isolates submitted to the public health laboratory are essential for surveillance of foodborne infections in the United States. Public health laboratories routinely serotype Salmonella and Shigella isolates, and routinely subtype all isolates of Listeria and Shiga toxin-producing E. coli (STEC) by pulsed-field gel electrophoresis (PFGE). Many also subtype representative samples of Salmonella and Shigella isolates with PFGE, among other foodborne pathogens. For more information on the national network of public health and food regulatory agency laboratories conducting molecular surveillance, visit the PulseNet website.

Guidance on E.coli to Healthcare Providers and Clinical Laboratories

Guidelines to ensure as complete as possible detection and characterization of STEC infections include the following:

• All stools submitted for testing from patients with acute community-acquired diarrhea should be cultured for STEC O157. These stools should be simultaneously assayed for non-O157 STEC with a test that detects Shiga toxins or the genes encoding these toxins.
• Clinical laboratories should report and send coli O157 isolates and Shiga toxin-positive samples to state or local public health laboratories as soon as possible for additional characterization.
• Specimens or enrichment broths in which Shiga toxin or STEC are detected, but from which O157 STEC are not recovered should be forwarded as soon as possible to a state or local public health laboratory so that non-O157 STEC can be isolated.
• Often, by the time a patient presents with HUS, the causative STEC can no longer be easily isolated from a stool specimen. For any patient with HUS without a culture-confirmed STEC infection, stool can be sent to a public health laboratory or to CDC through their public health laboratory for immunomagnetic separation (IMS) techniques that can increase the sensitivity of culture. In addition, with prior approval, serum can be sent through a state public health laboratory to CDC for serological testing for antibodies to some STEC serogroups.

To learn more: Visit the E. coli O157:H7 infections web page.