A bacterium closely related to E. coli caused an outbreak in China in 2023 but the probable contaminated food source was not identified. Researchers believe it to represent the first reported outbreak of gastroenteritis attributed to E. albertii outside of Japan.
Escherichia albertii infections typically cause watery diarrhea, abdominal pain, and fever, with most cases resolving without complications. E. albertii has often been misidentified as enteropathogenic or enterohemorrhagic E. coli (EPEC or EHEC), leading to the underestimation of infections.
In February 2023, an outbreak was reported in a junior high school in Hangzhou, Zhejiang province. In total, 22 out of 770 students were defined as suspected cases. The incubation period for infection ranged from 24 to 43 hours.
Findings were published in the journal Epidemiology and Infection.
According to the epidemiological investigation, all 770 students were in the third grade and had the same dinner on one day in February from a catering delivery company. Unfortunately, no food samples were kept for analysis.
Classes were suspended and students were sent home, with only individuals showing severe symptoms enrolled in the study.
Likely foodborne source not found
Sixteen environment smears – including samples from desk surfaces, the interiors of refrigerators, and water dispenser outlets – and 12 from food samples supplied on two other days in February were taken.
Meals for second- and third-year students were delivered by two different food companies. Only third-grade students were affected by the outbreak. Scientists said although E. albertii was not detected in food samples, contaminated food was the most probable vehicle for the outbreak.
Escherichia albertii strains were isolated from anal swabs collected from six patients. Each isolate was classified as sequence type ST2686.
To assess the relationships among outbreak strains in the study and other E. albertii strains, scientists retrieved 43 E. albertii genomes from the NCBI database and all available epidemiological information. The 43 strains were isolated from different sources in 13 countries between 1983 and 2022, including three ST2686 strains and six strains associated with previous outbreaks.
The six isolates from this study coalesced into a single, highly genetically related cluster. This implies a common origin for the isolates. Isolates were different from strains associated with six outbreaks in Japan. These results suggested that no known or dominant E. albertii types are predictive for outbreaks, and strains from multiple sources can potentially cause illness, said researchers.
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