Category Archives: E. coli O157:H7

E. coli O157:H7

E. Coli O157:H7 Hazelnuts

Outbreak: E. COLI O157:H7 HAZELNUTS
Product: Hazelnuts
Investigation Start Date: 02/07/2011
Location: Multi-State
Etiology: E. coli (STEC) O157:H7
Earliest known case onset date: 12/20/2010
Latest case onset date: 01/28/2011
Confirmed / Presumptive Case Counts: 8 / 0
Positive Samples (Food): 22
Outbreak Summary:
Eight outbreak cases of lab-confirmed E. coli O157:H7 were identified in Michigan, Minnesota, and Wisconsin. Initial, hypothesis generating interviews identified in-shell mixed nuts as a common exposure, specifically in-shell hazelnuts. A traceback investigation confirmed that the in-shell hazelnuts consumed by cases came from a common distributor which resulted in a press release and recall. Ultimately, the close collaboration between public health and agriculture agencies in multiple states, Centers for Disease Control and Prevention (CDC), and the United States Food and Drug Administration (FDA) allowed the identification of a novel vehicle for an O157 outbreak, with a very small number of detected cases.
Details:
A multi-state outbreak of E. coli O157:H7 infections associated with hazelnuts.

Background
On February 7, 2011, the Minnesota Department of Health (MDH) Public Health Laboratory (PHL) determined that two human clinical E. coli O157:H7 isolates submitted through routine surveillance had indistinguishable PFGE patterns. A review of the national PulseNet database revealed four additional human E. coli O157:H7 isolates with the outbreak PFGE pattern in two states (three in Wisconsin and one in Michigan). A multi-state investigation was initiated.

Results
Eight cases from three states were ultimately identified in this outbreak Minnesota (3), Wisconsin (4), and Michigan (1). All three Minnesota cases were male and had a median age of 62 years (range, 55 to 64 years). All three cases reported experiencing bloody diarrhea and cramps, two (66%) reported fever, one (33%) reported vomiting, and none reported fever. Two cases were hospitalized, each for 3 days. No cases developed hemolytic uremic syndrome and none died.

Upon initial interview, the first two Minnesota cases both reported consuming ground beef, sausage, lettuce, and nuts during the week prior to illness onset. Specific exposure information (i.e., brand and purchase location) collected on the ground beef, sausage, and lettuce consumed by the cases indicated these items were not from a common source. Upon re-interviews, all eight cases in the three states reported consuming in-shell hazelnuts also called filberts. Four case reported consuming hazelnuts as part of mixed nuts, and seven case reported purchased hazelnuts from bulk bins at grocery stores. One Wisconsin case reported purchasing packaged in-shell hazelnuts. However, further investigation at the grocery store where this product was purchased revealed that these hazelnuts were re-packaged at the store after originally being sold from a bulk bin.

A traceback investigation conducted by the Minnesota Department of Agriculture (MDA), in conjunction with the Michigan Department of Agriculture, California Food Emergency Response Team (CAL-FERT), and Wisconsin Department of Agriculture, Trade and Consumer Protection (WDATCP) found that the mixed nuts and in-shell hazelnuts purchased by cases originated from a single distributor, DeFranco and Son’s of California. On March 4, DeFranco and Sons issued a voluntary recall of all hazelnuts and mixed nut products distributed from November 2 through December 22, 2010. Recalled product was distributed to stores in seven states (Minnesota, Iowa, Michigan, Montana, North Dakota, South Dakota, and Wisconsin). A press release was issued on March 4, 2011 to inform the public.

In-shell hazelnuts collected by MDA from a case patient’s home tested positive for the outbreak PFGE subtype of E. coli O157:H7 on March 3, 2011. Additional mixed nut samples that included hazelnuts collected from recalled retail product by WDATCP and collected from DeFranco and Son’s by CAL-FERT also tested positive for the outbreak PFGE subtype of E. coli O157:H7. DeFranco and Son’s received hazelnuts from two companies in Oregon but did not maintain internal product traceability. The FDA conducted inspections of the two Oregon companies.

Conclusions
This was a multi-state outbreak of E. coli O157:H7 infections associated with eating in-shell hazelnuts grown in Oregon. Rapid collaboration between multiple state health departments and state departments of agriculture were crucial in identifying in-shell hazelnuts as the vehicle. This is the first documented outbreak of E. coli O157:H7 infections associated with nuts.

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E. coli O157:H7

Berry Stand Strawberries

Outbreak: Berry Stand Strawberries
Product: Strawberries
Investigation Start Date: 08/03/2011
Location: Clackamas, Multnomah, Washington, Clatsop & Yamhill Counties, Oregon
Etiology: E. coli (STEC) O157:H7
Earliest known case onset date: 07/01/2011
Latest case onset date: 07/29/2011
Confirmed / Presumptive Case Counts: 14 / 11
Positive Samples (Food / Environmental): 4 / 100
Hospitalizations: 6
Deaths: 2

Outbreak Summary:
This investigation implicated a novel vehicle—strawberries—as the cause of an outbreak of E. coli O157 infections. An association with locally produced strawberries quickly became apparent as cases were interviewed; but the fact that almost all had purchased them at roadside stands and farmer’s markets led to concern about potential confounding of some overlooked item sold at similar venues. The concern was laid to rest by visits to the stands, a case-control study, and traceback of the strawberries to a single Oregon farmer. Learning how the strawberries became contaminated was the fruit of field work: epidemiologists investigated the strawberry fields and found them heavily contaminated with deer feces, with a herd of deer seen grazing in the area. Culture of 50 environmental samples that contained visible deer pellets yielded E. coli O157 in 10 (20%), with PFGE patterns matching those of the cases.

This outbreak once again confirmed deer as key reservoirs for the pathogen. Interestingly, an additional PFGE-matched case was identified months later; the case hadn’t eaten the commercial strawberries but lived in the area where they were grown. Culture of a sample from this case household’s vacuum cleaning bag yielded a PFGE-matching strain of E. coli O157:H7, a testimony to the pathogen’s ability to survive for prolonged periods when dried.

Details:
The following is the abstract from the published article found here.

Editorial commentary can be found here.

BACKGROUND:
An outbreak of Escherichia coli O157:H7 was identified in Oregon through an increase in Shiga toxin-producing E. coli cases with an indistinguishable, novel pulsed-field gel electrophoresis (PFGE) subtyping pattern.

METHODS:
We defined confirmed cases as persons from whom E. coli O157:H7 with the outbreak PFGE pattern was cultured during July–August 2011, and presumptive cases as persons having a household relationship with a case testing positive for E. coli O157:H7 and coincident diarrheal illness. We conducted an investigation that included structured hypothesis-generating interviews, a matched case-control study, and environmental and traceback investigations.

RESULTS:
We identified 15 cases. Six cases were hospitalized, including 4 with hemolytic uremic syndrome (HUS). Two cases with HUS died. Illness was significantly associated with strawberry consumption from roadside stands or farmers’ markets (matched odds ratio, 19.6; 95% confidence interval, 2.9–∞). A single farm was identified as the source of contaminated strawberries. Ten of 111 (9%) initial environmental samples from farm A were positive for E. coli O157:H7. All samples testing
positive for E. coli O157:H7 contained deer feces, and 5 tested farm fields had ≥ 1 sample positive with the outbreak PFGE pattern.

CONCLUSIONS:
The investigation identified fresh strawberries as a novel vehicle for E. coli O157:H7 infection, implicated deer feces as the source of contamination, and highlights problems concerning produce contamination by wildlife and regulatory exemptions for locally grown produce. A comprehensive hypothesis-generating questionnaire enabled rapid identification of the implicated product. Good agricultural practices are key barriers to wildlife fecal contamination of produce.

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