Blood Type A Associated with More Severe E. Coli Infection

People with blood type A are more likely to develop severe illness from an Escherichia coli infection, according to a new multi-institutional study led by Washington University School of Medicine researchers.

E. coli bacteria naturally reside in human intestines and can be part of a healthy gut microbiome, but some forms of the bacteria are pathogenic. These include Shiga toxin-producing E. coli (STEC), enterotoxigenic E. coli (ETEC), enteropathogenic E. coli (EPEC), and enteroaggregative E. coli (EAEC), which are diarrheagenic and can cause severe stomach cramps, diarrhea, and vomiting. The Centers for Disease Control and Prevention (CDC) estimates that STEC causes 265,000 illnesses, 3,600 hospitalizations and 30 deaths in the United States each year. While anyone can become ill with these infections, children under the age of 5 years and adults who are 65 years and older are more likely to become seriously ill. The United States is currently experiencing its largest E. coli outbreak since 2006, one what has been linked with contaminated romaine lettuce.

ETEC is the leading cause of traveler’s diarrhea, one of the leading bacterial causes of diarrheal disease and the second leading cause of death worldwide among children under the age of 5 years. In a new study published on May 17 in The Journal of Clinical Investigation, researchers found that individuals with blood type A are more likely to develop severe cases of diarrhea compared with those who have blood types B or O. A prior study published in 2007 on children with ETEC infections in Bangladesh found that ETEC diarrhea was more prevalent in children with A and AB blood groups compared with those in O blood groups. The new study examined the molecular basis for varied presentations of ETEC infections, which can range from asymptomatic colonization to severe cholera-like illness.

The study authors — from the Washington University School of Medicine, Johns Hopkins University, U.S. National Institutes of Health, and the Naval Medical Research Center – conducted controlled infection trials on human volunteers. The researchers infected participants with ETEC strain H10407, which was originally isolated from a case of cholera-like illness, and observed them for 5 days. Participants with moderate to severe diarrhea received antibiotics, as did participants who did not experience illness, to clear the bacteria. Using data and blood samples from 106 volunteers, the researchers found that 81% of those with blood type A developed a more severe illness that required treatment, while only about half of volunteers with other blood types did. The H10407 strain of ETEC is one of many that secretes a novel adhesion molecule called EtpA, which the researchers discovered sticks to the sugars on the surface of red blood cells in individuals with blood type A, but not those with blood types B or O. EtpA makes it easier for the bacteria to attach to their intestinal walls and cause severe illness.

“We think this protein is responsible for this blood-group difference in disease severity,” said senior author James Fleckenstein, MD, in a recent statement from the Washington University School of Medicine. “A vaccine targeting this protein would potentially protect the individuals at highest risk for severe disease.”

The authors note that those not in blood group A are still at risk of developing diarrhea from a range of bacteria and viruses, and travelers should be sure to wash hands and drink only purified water to avoid becoming ill.