Home » Case Study » E. Coli O157 Outbreak Core Evidence Forensic File Case Study

E. Coli O157 Outbreak Core Evidence Forensic File Case Study

E. Coli O157 Outbreak Core Evidence Forensic File Case Study

Summary of Core Evidence Forensic File Case

In October 1996, in Seattle, Washington, a 2 ½-year-old boy, Michael Beverly was rushed to the hospital due to severe stomach pain and uncontrollable diarrhea. Doctors found a deadly pathogen called Escherichia Coli (E.COLI O157) in his blood.

Soon, there were about a dozen children admitted to the hospital with similar pathogenic infections. 

In Search of Source: To find the source of the outbreak, a team of doctors and investigators tighten up their belts and start questioning the families about their diets.

With numerous questionnaires, they found a common link. Most of the victim’s family members admitted to consuming unpasteurized Odwalla Apple Juice.

A Hint: However, there was no conclusive evidence that Odwalla Apple Juice was the source of the E.Coli O157 outbreak. But considering the safety of consumers, Odwalla removed their products from all stores when officials asked them to do so.

Investigators now have to prove their theory. For that, thousands of Odwalla Apple juices were tested for strains of E.Coli.

Finally One Possible Match: On November 4, 1996, one of the bottles tested positive for E.Coli. However, still, investigators have to prove that the bottle has the same stain as that in children.

For that DNA profile was compared and they were identical. This proves that Odwalla Apple juice was the source of  E. COLIO157 infection. 

With the bottle’s packing date, the batch of apples was traced back to an orchard. On investigation, an epidemic intelligence officer discovered deer prints and droppings in the sand that could be the source of E. Coli O157 the outbreak.

Odwalla was brought to trial and fined $1.5 million; they now sell pasteurized apple juice.

List all Victims in Case  

Name of VictimsAge of Victims
Michael Beverly 2 ½ Years
Brianne Kiner 
Anna Gimmestad 16 Months
12 more Children

How Investigators Suspected that the Possible Outbreak was from Odwalla Apple Juice?

Since E.coli is a foodborne disease, it was clear that the source of infection is some type of food item. So researchers created a questionnaire about food intake a week or two before developing symptoms.

After a series of questions with the family members of infected children, investigators found that all children had consumed Odwalla Apple Juice. But there was no scientific proof to support their obligations.

Thousands of bottles were examined, and one bottle dated 7 October 1996, tested positive for E. Coli bacteria.

How Investigators Suspected that the Possible Outbreak was from Odwalla Apple Juice

How does DNA Testing help in Detecting the Origin of the E. Coli O157 Strain?

When it was identified that Odwalla apple juice also had E. COLI O157 strain, now, investigators had to establish that the bacterial strains present in Odwalla apple juice bottles and in infected individuals were the same.

For this, they used DNA Fingerprinting to generate DNA profiles of E. Coli. 

About Enterobacteriaceae Coli (E. Coli) O157

important information of E. Coli O157

Common facts about E. coli O157 strain.

  • Most Predominant Serotype: In the USA, E. coli O157:H7.
  • Pathotype Toxins Produced: Shiga toxin (STEC)/ Enterohemorrhagic toxin (EHEC).
  • Four Toxin Products: Stx1, Stx2, Stx2c, and Stx2d.
  • Borne type: Foodborne diseases, particularly diarrheal disease.
  • Key E. coli/host interactions: Attachment to intestinal cells and production of attaching, and effacing lesions (ability to adhere to the small intestinal mucosa and produce a striking).
  • Common Symptoms: cause mild diarrhea to severe kidney complications, severe abdominal pain, hemolytic uremic syndrome (HUS), acute renal failure in children, thrombocytopenia, acute nephropathy, seizures, coma, and death.

Instrument and Method Used

Pulsed-Field Gel Electrophoresis (PFGE):

  • PFGE is the most common technique to generate a DNA profile of microorganisms.
  • Highly effective subtyping tool for discriminating isolates at a subspecies level i.e. strains.
  • A common method for subtyping foodborne bacterial diseases.

Procedure For Strain Typing of E. Coli O157

  1. In agarose PFGE plugs, bacterial cells are suspended and treated with cell lysis/proteinase K buffer.

Use: Proteinase K buffer is used to disrupt cell walls and inactivate endogenous nucleases that may interfere with the process.

Procedure For Strain Typing of E. Coli O157 core evidence forensic file case
  1. Wash the PFGE plugs several times, to remove cellular debris.
  2. Cleaved the highly purified intact genomic DNA into large variably sized fragments (macrorestriction fragments) using an enzyme (Xbal and Blnl restriction enzymes used for E. coli O157: H7 and non-O157 serotypes)

Note: Ideally, a restriction enzyme is used that cleaves intact genomic DNA, yielding a small number of large fragments ranging in size from 20 kb to >1 Mb.

  1. Using gel electrophoresis with alternating current, macrorestriction fragments are separated.

Note: To ease the process of separation of large DNA fragments (>20kb), alternating current is preferred over conventional static current.

5. The gel is fluorescently stained and visualized under UV as a series of bands.

Note: Different bands represent different molecular weight fragments of DNA.

Comparison of Banding Patterns

Comparison of Banding Patterns of ecoli

The recovered restriction band pattern is used as a fingerprint to isolate comparison with the reference profile or pattern. In this case, the band pattern from E. coli patients matches with that of E. coli type in Odwalla Apple Juice.

Why are Odwalla’s Products now Pasteurized? What does Pasteurization do with Bacterial Growth?

If It Is Not Fresh-Squeezed, Then It Is Not  Odwalla

Odwalla company’s Mission Statement.

The Odwalla company believes that pasteurization degrades juice flavor. So, they never pasteurize their juices.

Pasteurization is a method of partial sterilization of a product to make it safer for consumption. This majorly includes heating to a temperature high enough (mostly it is lower than 100° C) to kill any bacteria, and inhibits their growth.

Odwalla did not follow this procedure, which resulted in the E.coli O157 outbreak in Seattle, Washington.

Similar Cases of E. Coli in the USA

SerotypeYearNo. of VictimsFood Source
E. coli O121201335Frozen food product
E. coli O157201333Ready-to-eat salads
E. coli O157201319Watercress
E. coli O157: H7201233Organic spinach and spring mix blend
E. coli O26201229Raw clover sprouts
E. coli O157: H7201158Romaine lettuce
E. coli O157: H7201038Cheese
E. coli O157: H7200943Beef
E. coli O157: H7200977Ready to bake cookie dough
E. coli O157: H72006199Fresh spinach
E. coli O10420114075 (France, Germany, USA)Fenugreek sprouts
E. coli O1572011250 (UK)Vegetables and soil

General FAQ

What was the possible origin of E.coli 0157 in Odwalla’s juice?

According to Dr. Sara Cody, who was an epidemic intelligence officer that investigate the Orchard, the possible source of origin of E.coli O157 could be deer droppings at the Orchard. Possibly, Orchard workers pick up ground-drop apples and send them back to Odwalla for processing them for juice.

Does Pasteurization make Odwalla’s Juice safer?

Yes, going through the pasteurization process, kills and inhibits the growth of bacteria to a great extent, this would surely make it safer.

What were the penalties paid by Odwalla’s Juice?

The Odwalla Company was fined $1.5 million, which was one of the highest fines ever imposed in a food poisoning case.

Why DNA Fingerprints of E. Coli is important even if one bottle of Odwalla’s has a possible match?

Even one of Odwalla’s Apple juice bottles was found to be E. coli, it doesn’t mean that it was the same strain that causes E. Coli bacterial infections in children. In short, they need to prove that they have a common origin. Because it was possible that the E. Coli in children differed from what they found in Odwalla’s juice bottle. To prove both are the same, DNA profiling was done.

Is E. Coli a deadly bacteria?

Many strains of E. coli are harmless and even provide many health benefits to humans. Only a small group of E. Coli bacteria can produce pathogenic toxins that harm humans and cause severe diarrheal disease.

Reference:

  • Forensic Files – Season 4, Episode 10 – Core Evidence [FilmRise True Crime]
  • Verotoxigenic Escherichia coli from animals, humans and foods: who’s who? [Pubmed]
  • Detection and Typing Strategies for Pathogenic Escherichia coli by Lucia Rivas, et.al. [Book]
  • Non-O157 Shiga toxin-producing Escherichia coli in foods. J Food Prot [Researchgate]
  • Enterotoxigenic Escherichia coli isolated from food [Pubmed]

Read More:

Leave a Comment

Your email address will not be published. Required fields are marked *