Your blood type might make you more likely to get traveler’s diarrhea

E. coli has a type and it isn’t pretty. The bacterium is more likely to cause severe diarrhea in people with type A blood.

An illness-causing strain of E. coli secretes a protein that gloms onto the sugar molecules that decorate type A blood cells, but not type B or O cells. These sugar molecules also decorate cells lining the intestines of people with type A blood and appear to provide a handle for the bacterium to latch onto before injecting its diarrhea-causing toxins, researchers report May 17 in the Journal of Clinical Investigation.

There were hints that blood type was linked to the severity of E. coli infection. But a clear connection was lacking until now, says a team led by researchers at Washington University School of Medicine in St. Louis.

Collaborators at Johns Hopkins University gave 106 healthy volunteers water laced with a strain of E. coli isolated from a person in Bangladesh with severe diarrhea. Within five days, 81 percent of the type A or AB volunteers developed moderate to severe diarrhea compared with roughly half the people with blood types O or B. (Everyone received antibiotics to clear the bacterium).

This discovery suggests that a vaccine targeting the bacterial protein — which is found in many E. coli strains — could be effective. That could help not only travelers but also children in the developing world, where repeated infections are linked to malnutrition and stunted growth. E. coli isn’t the only microbe that can cause severe diarrhea, though, making good hygiene — washing hands and purifying water — still the best defense.