Shigatoxigenic and verotoxigenic Escherichia coli

Shigatoxigenic and verotoxigenic Escherichia coli (STEC and VTEC), also known as E. coli O157:H7 among other serotypes, are strains of the bacterium Escherichia coli that produce either Shiga toxin or verotoxin. These toxins can cause severe foodborne illness in humans, leading to symptoms ranging from mild gastroenteritis to life-threatening conditions such as hemolytic uremic syndrome (HUS). The terms "Shigatoxigenic" and "verotoxigenic" refer to the production of toxins that are similar to those produced by Shigella dysenteriae, a bacterium that causes dysentery.

Epidemiology

STEC and VTEC infections are a significant public health concern worldwide. These bacteria are commonly found in the intestines of healthy cattle and can contaminate meat during slaughter and processing. Other sources of infection include consumption of contaminated water, raw milk, and unpasteurized juice, as well as direct contact with animals in agricultural settings. Outbreaks have also been associated with fresh produce such as lettuce and spinach. The most notorious outbreak occurred in 2011 in Germany, caused by the serotype O104:H4, which was linked to fenugreek sprouts and resulted in numerous cases of HUS and several deaths.

Pathogenesis

The pathogenicity of STEC and VTEC is primarily due to their production of Shiga toxin or verotoxin. These toxins inhibit protein synthesis in host cells, leading to cell death. The damage to the intestinal lining causes bloody diarrhea, and in severe cases, the toxins can enter the bloodstream and cause damage to other organs, most notably the kidneys, leading to HUS. HUS is characterized by hemolytic anemia, acute kidney failure, and a low platelet count, and it represents the most severe complication of STEC and VTEC infections.

Symptoms

The symptoms of STEC and VTEC infections can range from none at all to severe. The most common symptoms include severe abdominal cramps, diarrhea (which can become bloody), vomiting, and sometimes fever. Symptoms usually begin 3 to 4 days after exposure to the bacteria but can start anywhere from 1 to 10 days after exposure. In cases where the infection leads to HUS, symptoms might also include decreased frequency of urination, feeling very tired, and losing color in cheeks and inside the lower eyelids.

Prevention

Prevention of STEC and VTEC infections involves proper food handling and preparation practices, such as cooking meat thoroughly, avoiding cross-contamination between raw meat and other foods, washing fruits and vegetables before eating, and avoiding the consumption of raw milk and unpasteurized juices. Good hand hygiene, especially after contact with animals or their environments, is also crucial in preventing the spread of these bacteria.

Treatment

There is no specific treatment for STEC and VTEC infections. Antibiotics are generally not recommended, as they may increase the risk of developing HUS. Treatment focuses on symptom management, including hydration and, in severe cases, hospitalization for supportive care such as dialysis for kidney failure and blood transfusions for anemia. Early recognition and supportive treatment can improve outcomes in patients with HUS.