Complete the pathogen cluster along with Salmonella and Listeria monocytogenes.
What is Escherichia coli?
Escherichia coli (E. coli) is a bacterium that normally inhabits the intestine of humans and animals. The vast majority of its strains are harmless and are part of the normal intestinal flora; only a small group of pathogenic strains can cause illness.
What is STEC?
STEC (Shiga toxin-producing E. coli) is the group of pathogenic strains capable of producing Shiga toxin, the most clinically relevant variant within E. coli. This toxin can damage the intestinal lining and, in the most severe cases, the kidneys.
Which foods pose the greatest risk?
The risk is concentrated mainly in undercooked ground beef, leafy green vegetables irrigated or washed with contaminated water, unpasteurized raw milk and, to a lesser extent, untreated recreational or drinking water.
Consequences of a STEC infection
Most cases cause diarrhea, sometimes bloody, that resolves without specific treatment. In young children and older adults, however, it can progress to hemolytic uremic syndrome (HUS), a serious complication that affects kidney function and requires hospitalization.
How is E. coli / STEC detected in a laboratory?
Traditional culture
Isolation on selective media followed by biochemical and serological confirmation; this can take several days and the result is usually expressed in CFU for general counts of E. coli or coliforms.
Molecular methods
PCR targeting the genes encoding Shiga toxin (stx1, stx2) makes it possible to confirm whether a strain is STEC within hours, without depending on full isolation of the microorganism.
Control measures in the food industry
Adequate cooking of ground beef, microbiological control of irrigation and wash water for fresh produce, hygienic handling of raw meat to avoid cross-contamination, and environmental monitoring in plants that process these products.
Conclusion
E. coli is, for the most part, a harmless bacterium, but STEC strains represent one of the most serious risks in ground beef, fresh vegetables and unpasteurized dairy. Distinguishing a pathogenic strain from a harmless one is precisely the role of molecular methods targeting its toxin genes.
About TAAG
Discover how TAAG's molecular diagnostics services support the detection of enteric pathogens, including STEC strains.
Frequently asked questions
Is every E. coli strain dangerous?
No. Most E. coli strains are harmless and are part of the normal intestinal flora; only a small group, such as STEC, produces toxins that cause illness.
What is hemolytic uremic syndrome (HUS)?
A serious complication of STEC infection that affects kidney function, more common in young children and older adults, and that can require hospitalization.
How is a STEC strain distinguished from other E. coli in the laboratory?
Through PCR targeting the Shiga toxin genes (stx1/stx2), which confirms whether the isolated strain has the potential to produce this toxin.