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A positive Escherichia coli (E. coli) O157:H7 result is one of the most significant findings in food pathogen testing.

Whether detected in meat products, raw pet food, ingredients, or environmental samples, the result requires immediate attention and investigation.

However, understanding the result is the first step.

Key questions include:

  • Where was the organism detected?
  • What product was involved?
  • Was the result from product or environmental testing?
  • What additional actions may be required?

PBR Laboratories helps manufacturers understand results, evaluate contamination risks, and support informed food safety decisions.

WHAT IS ESCHERICHIA COLI (E. COLI) O157:H7?

Escherichia coli (E. coli) O157:H7 is a specific strain of Shiga Toxin-Producing Escherichia coli (STEC).

Unlike generic E. coli, which is often used as an indicator organism, E. coli O157:H7 is considered a foodborne pathogen.

Testing is commonly performed for:

  • Meat products
  • Poultry products
  • Raw pet food
  • Ingredients
  • Environmental monitoring programs
  • Food safety verification programs
WHAT IS THE DIFFERENCE BETWEEN GENERIC E. COLI AND E. COLI O157:H7?
Generic Escherichia coli (E. coli)

Typically used as an indicator organism.
May help evaluate:
• Sanitation effectiveness
• Process control
• Environmental hygiene

Generally reported as counts such as:
• CFU/g
• CFU/mL

Escherichia coli (E. coli) O157:H7

A specific pathogenic strain.
Typically reported as:
• Detected
• Not Detected

Used to evaluate food safety risks rather than general hygiene conditions.

WHAT IS STEC?

STEC stands for:
Shiga Toxin-Producing Escherichia coli

This group includes:
Escherichia coli O157:H7
Non-O157 STEC strains

Many food safety programs test for both O157:H7 and non-O157 STEC organisms.

HOW ARE E. COLI O157:H7 RESULTS REPORTED?

Results are generally reported as:

Detected

The organism was identified in the analyzed sample.

Not Detected

The organism was not identified under the conditions of the test.

Unlike routine microbiological indicators, results are not typically reported as numerical counts.

WHERE WAS THE POSITIVE RESULT FOUND?

The significance of a positive result depends on the sample type.

FINISHED PRODUCT RESULTS

Detection in finished product generally requires immediate investigation.

Questions To Ask

  • Is the product ready for distribution?
  • Are additional lots affected?
  • Are ingredients involved?
  • Are environmental sources possible?

Decisions Supported

  • Product evaluation
  • Food safety investigations
  • Corrective actions
RAW MATERIAL RESULTS

Positive findings in ingredients may indicate contamination introduced before processing.

Questions To Ask

  • Which supplier provided the ingredient?
  • Are other lots affected?
  • Are supplier controls adequate?

Decisions Supported

  • Supplier verification
  • Ingredient risk assessments
  • Receiving controls
ENVIRONMENTAL SWAB RESULTS

Positive environmental findings may indicate contamination sources within the facility.

Common Sampling Locations

  • Equipment
  • Floors
  • Drains
  • Processing areas
  • Food contact surfaces

Decisions Supported

  • Environmental investigations
  • Expanded monitoring
  • Corrective actions
FOOD CONTACT SURFACE RESULTS

Positive findings on food contact surfaces require immediate attention.

Questions To Ask

  • Was sanitation effective?
  • Could product have been exposed?
  • Is contamination recurring?

Decisions Supported

  • Sanitation verification
  • Product evaluations
  • Expanded sampling

COMMON SOURCES OF E. COLI O157:H7 CONTAMINATION

Raw Animal Products

One of the most common contamination sources.

Cross-Contamination

Movement of contamination between products, equipment, or production areas.

Environmental Reservoirs

Contamination persisting within the processing environment.

Inadequate Sanitation

Insufficient cleaning and sanitation procedures.

Ingredient Sources

Incoming materials may introduce contamination.

WHAT SHOULD YOU DO AFTER A POSITIVE RESULT?

1
Step 1 – Review The Result

Confirm:
Sample identification
Product information
Sample location
Historical results

2
Step 2 – Assess Product Impact

Determine:
Products potentially affected
Production dates
Lot relationships

3
Step 3 – Review Environmental Data

Evaluate:
Previous positives
Monitoring trends
Environmental findings

4
Step 4 – Conduct Additional Testing

Expanded testing may help identify:
Extent of contamination
Potential sources
Impacted areas

5
Step 5 – Investigate Root Causes

Perform Root Cause Investigations in Food Manufacturing to determine how contamination entered and where it spread.

6
Step 6 – Review Preventive Controls

Assess:
Monitoring programs
Sanitation programs
Supplier controls
Verification activities

WHAT DOES A RECURRING POSITIVE RESULT MEAN?

Repeated positive findings may indicate:

  • Persistent Environmental Sources: Contamination may be surviving routine cleaning procedures.
  • Facility Design Challenges: Certain areas may support long-term contamination.
  • Traffic Flow Issues: Personnel or equipment movement may contribute to spread.
  • Incomplete Corrective Actions: Underlying causes may not have been fully addressed.

INDUSTRIES COMMONLY TESTING FOR E. COLI O157:H7

Meat Processors

Routine pathogen verification programs.

Poultry Processors

Food safety and environmental monitoring programs.

Raw Pet Food Manufacturers

Finished product and environmental testing.

Ingredient Manufacturers

Supplier verification and risk management.

Food Manufacturers

Food safety verification and contamination prevention programs.

WHAT DECISIONS DOES E. COLI O157:H7 TESTING SUPPORT?

  • Product Release Decisions: Evaluate product safety risks.
  • Supplier Verification Programs: Assess incoming ingredient risks.
  • Environmental Monitoring Programs: Identify contamination sources.
  • Corrective Action Programs: Support contamination investigations.
  • Food Safety Verification: Confirm effectiveness of preventive controls.

COMMON MISCONCEPTIONS

  • "Generic E. coli and E. coli O157:H7 Are The Same"
    False. Generic E. coli is commonly used as an indicator organism, while E. coli O157:H7 is a pathogen.
  • "A Positive Result Explains The Entire Problem"
    False. Additional investigation is usually required.
  • "Environmental Results Are Less Important"
    False. Environmental monitoring often provides critical information regarding contamination sources.
  • "One Positive Result Means The Entire Facility Is Contaminated"
    False. The extent and significance of contamination must be determined through investigation and follow-up testing.

WHY E. COLI O157:H7 TESTING MATTERS

Testing helps organizations:

• Identify contamination risks
• Verify food safety programs
• Evaluate supplier performance
• Investigate contamination events
• Support corrective actions
• Protect consumers

The goal is not simply to detect contamination.

The goal is to understand contamination sources and prevent recurrence.

FAQ

A pathogenic strain of Shiga Toxin-Producing Escherichia coli (STEC).

Typically as Detected or Not Detected.

No. Generic E. coli is often used as an indicator organism, while O157:H7 is a pathogen.

Meat products, poultry products, raw pet food, ingredients, and environmental samples.

Review product impact, evaluate environmental data, conduct follow-up testing, and investigate root causes.

Environmental monitoring may identify contamination sources before they affect products.

Need Help Understanding Escherichia coli (E. coli) O157:H7 Results?

PBR Laboratories provides E. coli O157:H7 testing, Shiga Toxin-Producing Escherichia coli (STEC) testing, food pathogen testing, environmental monitoring, food microbiology testing, and contamination investigation support throughout Alberta, Western Canada, and Canada.

Contact PBR to discuss results, food safety objectives, monitoring programs, follow-up testing requirements, and contamination investigations.

Contact PBR Laboratories

Choose PBR – Because Precision Matters, Defining Excellence in Laboratory Services Since 1984.