In addition, E. albertii closely resembles E. coli in its phenotypic characteristics. Retention of the major virulence factor intimin in E. albertii is well established, whereas little is known about the incidence of Shiga toxin (Stx)-producing E. albertii (STEA). Stxs are the most significant virulence factors of Stx-producing E. coli (STEC) in human infections. However, STEC strains that produce intimin, a host-cell adhesin, often cause more critical symptoms in patients than STEC strains that do not produce intimin.

Several studies have investigated the environmental prevalence, detection possibilities, genomes and pathogenicity potential of STEA strains.

STEA has been isolated from various animals: pigs, cats and birds, but the natural reservoir of E. albertii is still unclear; this information would be essential to determine the transmission dynamics and to prevent E. albertii infections. Given that patients in clinical outbreaks in Japan might be infected through waters (spring and well waters) or vegetables, but not meats, the natural reservoirs of STEA may not be the major food animals (e.g. cattle and chicken, the reservoirs of Shiga toxin-producing E. coli and Campylobacter spp). The role of wildlife, which may contaminate water and vegetables, has also been raised. In a Japanese study from 2020, STEA was detected by PCR in 248 (57.7%) out of 430 racoons from Osaka, and 143 STEA strains were isolated from 62 PCR-positive samples. In addition to Japan, STEA has been clinically isolated from samples in other countries where raccoons reside. Interactions between raccoons and other animals such as wild mice and wild boars can also be possible.

In another study (IAFP Europe 2020 abstract, US authors, not available online and not yet published), STEA strains were isolated from wild birds in a leafy greens-growing region in California. All E. albertii strains encoded intimin and possessed genes encoding type II cytolethal distending toxin (CDT), a subtype prevalent in clinical strains. According to the authors, the data suggest that hypervirulent STEA strains are present in wild birds, which may serve as a pathogen reservoir in a leafy greens-preharvest environment.

Other studies focus on the detection problems of STEA. Hinenoya and colleagues (2020) developed a selective medium for E. albertii named XRM-MacConkey agar, which is a modified MacConkey agar supplemented with xylose (X), rhamnose (R) and melibiose (M) instead of lactose. All the 49 E. albertii tested were detectable, with a limit of detection of 10⁵ CFU/g from faecal samples.

The case was presented by the DFI representatives at the EREN meeting in Spring 2021. Several of the Member States indicated that they were not aware of the problem of E. albertii, therefore there are no data on its occurrence, and it is not currently being discussed by FAO or EFSA. Slovakia has indicated that they are aware of the problem, one of their laboratories has identified MDR E. albertii in a sample of vegetarian consumers, so they believe that the issue of leafy vegetables could be important. Denmark is also aware of cases of STEA.

After the discussion the main conclusions were:

• the gene sequence is detected by PCR identification, but we do not know which species has been identified (E. coli or E. albertii);
• no data are available on the route of infection, growth, mortality parameters and incidence of STEA;
• ECDC does not collect STEA data.

EREN classified the case as emerging issue, and based on its recommendations it urges Member States to collect data on E. albertii.