Researchers have raised questions about the threat Yersinia enterocolitica poses to public health.

The study, involving the Quadram Institute, University of East Anglia, and the UK Health Security Agency (UKHSA) found diverse populations of Yersinia enterocolitica on foods.

The number of yersiniosis cases is low, but it is likely there is underreporting. Not everyone with gastroenteritis reports it; such patients aren’t routinely screened for Yersinia.

Yersinia enterocolitica was isolated from 37 of 50 raw chicken, 8 of 10 pork and salmon samples, and 1 of 10 leafy green samples collected at retail in the UK in 2021.

The percentage of food contamination was higher than in past studies looking at Campylobacter and Salmonella, but Yersinia enterocolitica causes fewer reported infections than these bacteria.

Another study, published in the journal Eurosurveillance in 2023, estimated thousands of Yersinia enterocolitica infections may go undiagnosed in England annually.

In the new work, researchers used multiple methods to determine the diversity of Yersinia enterocolitica in different foods and if it contributed to human infections.

According to the study published in the International Journal of Food Microbiology, understanding the types of Yersinia enterocolitica found on food samples is essential for outbreak investigations.

Potential role in infection
From the 80 food samples, 207 Yersinia enterocolitica isolates were recovered and their genomes sequenced. Isolates from food belong to 38 sequence types (ST).

The 207 genomes from food were compared with 747 public Yersinia enterocolitica genomes. Of the 207 food-derived isolates recovered in the study, 205 were biotype 1A. Biotype 1A is considered non-pathogenic because it lacks virulence genes, but outbreaks with this biotype have been reported.

Of the 80 food samples tested, 41 contained isolates that belonged to the same ST that had previously been isolated from UK human sources.

Just because highly similar Yersinia enterocolitica biotype 1A isolates were found in clinical and food specimens does not mean they were the agent responsible or that the isolate originates from that food type, said researchers.

“Effective source attribution of Yersinia enterocolitica will require improved detection and reporting of Yersinia enterocolitica from humans, and surveillance of food with sufficient isolates taken to capture the diverse populations present; this will also help determine the clinical significance of biotype 1A.”

Findings suggest that food samples were contaminated with a diverse population of Yersinia enterocolitica at a single point or at multiple points with different strains. 

“The large amount of diversity found amongst samples has implications for outbreak analysis, as sampling a single Yersinia enterocolitica isolate from a food sample will unlikely represent the diverse population present and could result in potential sources of infection being missed,” said scientists.