Scientists probing the deadly Escherichia coli strain in Europe said the bacteria combines a highly poisonous but common toxin with a rarely seen “glue” that binds it to a patient’s intestines.
It may take months for the global team of researchers to fully understand the characteristics of the bacteria that has killed at least 17 people in Europe and sickened 1,500, but they fear this E. coli strain is the most toxic yet to hit a human population.
Most E. coli bacteria are harmless. The strain that is sickening people in Germany and other parts of Europe, known as O104:H4, is part of a class of bacteria known as Shiga toxin-producing Escherichia coli, or STEC.
This class has the ability to stick to intestinal walls where it pumps out toxins, causing diarrhea and vomiting. In severe cases, it causes hemolytic uremic syndrome, or HUS, attacking the kidneys and causing coma, seizure and stroke.
“Germany is now reporting 470 cases of HUS. That is absolutely extraordinary,” said Robert Tauxe, a foodborne diseases expert at the US Centers for Disease Control and Prevention (CDC).
The CDC has been working with German health authorities on the case since late last week.
“That is 10 times more than the largest outbreak in this country,” he said, referring to a 1993 outbreak involving fast-food hamburgers that sickened more than 700 people and killed four. In that outbreak, there were 44 cases of HUS.
Asked if this was the world’s deadliest E. coli outbreak yet, Tauxe said: “I believe it is.”
He said a strain very similar to the German strain had been seen in South Korea in the 1990s, but is very rare.
Remarkably, the German strain appears to combine the toxin found in the most common type of STEC bacteria in the US, known as E. coli O157:H7, with an unusual binding agent. Tauxe said that “glue” was typically only found in children in the developing world.
“The glue that this bug is using is not the same glue that is E. coli O157 or most other STEC bacteria,” he said.
“It’s this combination from the glue from another kind of E. coli and the shiga toxin that makes this an unusual strain,” he said.
The WHO has confirmed that the strain “has never been isolated from patients before” and said the bacteria had likely acquired some extra genes that may make it especially deadly.
The source of the outbreak is unknown, but scientists say it is highly likely to have originated in contaminated vegetables or salad in Germany.
E. coli infections are spread by consuming even minuscule particles of feces of infected animals or humans, often via contaminated food or water.
Tauxe said the CDC had notified public health officials in all US states to be on the lookout for the infections. So far, three US adults have developed HUS after having traveled to northern Germany, the CDC said late on Thursday.
The CDC also said the Pentagon had been notified about the outbreak because of the presence of US military bases in Germany, but added that there are no known cases among US military personnel.
US health officials have not confirmed that the infections match the German strain, but Tauxe said it is very likely they are part of the same outbreak and more tests are being done to see if the infections have the same fingerprint.
Tauxe would not release the individuals’ names or say where they lived.