Blood Type Linked to Severity of Diarrhea

Some people infected with the bacterium develop severe, cholera-like, watery diarrhea that can be lethal. Others experience unpleasant symptoms but recover easily, while some do not get sick at all. A new study shows that a kind of E. coli most associated with "travelers' diarrhea" and children in underdeveloped areas of the world causes more severe disease in people with blood type A.

A team of scientists led by those at Washington University School of Medicine (St. Louis, MO, USA) carried out controlled human infection clinical trials, and gave healthy volunteers a dose of an E. coli strain originally isolated from a person in Bangladesh with severe, cholera-like diarrhea. Then, they observed the volunteers for five days. Those who developed moderate to severe diarrhea were treated with antibiotics. The disease comes on quickly, so anyone who was still healthy at the end of five days was unlikely to get sick later. Nonetheless, any remaining healthy participants also were given antibiotics to clear the bacteria before going home.

The investigators obtained data and blood samples from 106 people, each of whom participated in one of four such studies. They found that people with blood type A got sick sooner and more seriously than those of other blood types. More than eight out of 10 (81%) of blood group A people developed diarrhea that required treatment, as compared with about half of people with blood group B or O. They found that the bacteria produce a specific protein that sticks to A-type sugars, but not B- or O-type sugars, on intestinal cells. Since the protein also sticks to E. coli, it effectively fastens the bacteria to the intestinal wall, making it easy for them to deliver diarrhea-causing toxins to intestinal cells.

F. Matthew Kuhlmann, MD, a clinical investigator and a senior author of the study, said, “I don't want anyone to cancel their travel plans to Mexico because they have type A blood, Or the converse: I don't want anyone to think they're safe because their blood group is not A. There are a lot of different species of bacteria and viruses that can cause diarrhea, so even though this blood-group association is strong, it doesn't change your overall risk. You should continue taking the same precautions whatever your blood type.” The study was published on May 17, 2018, in The Journal of Clinical Investigation.

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