A type of E. coli similar to what caused a large outbreak in 2011 has recently been detected in Europe, according to researchers.

Two cases of Shiga toxin-producing Enteroaggregative E. coli (EAEC) O104:H4 were reported in the Netherlands in 2019 and 2020 and in one food isolate from 2017. There was also a patient from Austria in 2021.

In 2011, a huge outbreak caused by STEC O104:H4 occurred in Europe, mainly Germany and France, that was associated with sprouts grown from fenugreek seeds from Egypt. The outbreak resulted in more than 4,000 infections and 54 deaths from 16 countries, including six cases in the United States.

After this outbreak, only a few sporadic infections with EAEC O104:H4 were reported, most related to travel to Turkey or North Africa, said the study published in Emerging Infectious Diseases.

The two recent cases in the Netherlands involved middle-aged women with abdominal cramps and bloody diarrhea. They did not have recent travel. The 2019 patient consumed cooked minced beef, and the 2020 case ate beef, hamburger meat, and vegetables and fruits from her own garden.

In 2021, the Austrian Agency for Health and Food Safety (AGES) obtained a sample from a 10-year-old girl with hemolytic uremic syndrome (HUS). This patient also reported no recent travel, but she had consumed raw veal. Also, EAEC O104:H4 was found in a sample from pig meat in 2017 in the Netherlands. 

Researchers said it was surprising to retrieve an isolate from a pork product. However, it does not necessarily mean that pigs are a reservoir, because contamination could have originated from a food handler or contaminated feed rather than the pigs.

Sporadic occurrence of related E. coli
Since 2016, shiga toxin-producing E. coli isolates in the Netherlands have been whole genome sequenced to detect clusters and outbreaks nationwide. During retrospective analysis of whole genome sequencing data, two EAEC O104:H4 cases were identified in 2019 and 2020.

Scientists compared the recently found isolates, two shiga toxin-producing EAEC O104:H4 isolates from patients in the Netherlands from 2013 and representative isolates from patients in Germany who shed the outbreak strain into 2012.

The 2020 patient isolate from the Netherlands and the pork isolate clearly clustered with the representative outbreak isolates, according to researchers.

However, patient isolates from the Netherlands in 2019 and Austria in 2021 appeared more similar to each other and the two isolates from Dutch patients in 2013 than to those from the outbreak cluster.

Genomic analysis of several post-outbreak EAEC O104:H4 isolates suggests they are not derived from the 2011 outbreak but share a recent common ancestor. The analysis indicates that variants of Shiga toxin-producing EAEC O104:H4 are circulating worldwide.

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