Escherichia coli on fresh produce 

Escherichia coli (E. coli) are gram-negative, rod-shaped bacteria that cause a great number of food-borne illnesses annually. For example, according to PHAC, there were 470 reported cases of E. coli O157:H7 infections in Canada in 2013, which was the third highest among all pathogenic bacteria. Although E. coli infection is often referred to as “hamburger disease”, these bacteria also contaminates fresh produce. Earlier this year (between March 13 and 31), there were several E. coli infections cases identified in Canada, majority (9 out of 12 cases) of which were reported in Alberta. More investigations by CFIA are underway, however, leafy greens are considered to be the most possible cause of infections. Depending on strains, consequences of E. coli infections vary. Most people suffer from stomach discomfort, diarrhea and vomiting. Those who are infected with pathogenic strains such as O157:H7 may develop more severe symptoms, such as kidney failure.

In addition to bacterial contamination, a research done by a group of UBC researchers shows a concerning fact that 97% of E. coli isolated from leafy greens samples purchased from several farmers market in Vancouver were antibiotic-resistant. To be more specific, antimicrobial resistance of E. coli on fresh green, red, and romaine lettuce samples were evaluated. 58% of samples were resistant to amikacin, 48% were resistant to trimethoprim and 45% were trimethoprim-sufamethoxazole-resistant. Resistance to nalidixic acid, kanamycin, ampicillin, amoxicillin-clavulanic acid, cefoxitin, gentamicin and tetracycline were also found. Luckily, only 13% of samples were found to be contaminated with trace amount of E. coli and the microbiological quality of produce was acceptable according to Health Canada guidelines.

You can read more about the 12 E. coli cases in Canada here:

The use of antimicrobial agent on food animal (e.g. chicken) is one possible cause of antibiotic-resistance in E. coli on fresh produce. Antimicrobial agent is used to promote growth of food animal. Nonetheless, only 10% of the drug would be absorbed by animals and the rest will be excreted. As the wastes are applied as fertilizers. Antibiotics are also introduced to the environment (e.g. soil, water) and vegetables. Antibiotics selects for drug-resistant bacteria on leafy produce, which leads to predominant of antibiotic-resistant bacteria. Additionally, contaminated irrigation water, poor personal hygiene and inadequate food processing also adversely affect microbiological safety of greens.

To protect ourselves from E. coli contaminations on vegetables, the following precautions can be taken:

  • Wash produce thoroughly before consumption
  • Clean and sanitize food-contact surfaces properly, including cutting boards, knifes, etc.
  • Wash hands for at least 20 seconds with warm water and soap regularly during food handling
  • Keep raw meat and vegetables separated to avoid cross-contamination
  • Store food at refrigerating temperature (< 4 ͦC) to inhibit bacterial growth

For more information about E. coli, see: