# Seek and you shall find: Yersinia enterocolitica in Ireland’s drinking water

## TL;DR

This study found three Yersinia species in Irish drinking water, two of which are newly described and non-pathogenic, highlighting the need for advanced sequencing in public health labs.

## Contribution

The study identifies two isolates as Yersinia proxima and one as non-pathogenic Yersinia enterocolitica clade 1Aa using whole genome sequencing.

## Key findings

- Three Yersinia isolates were identified in Irish drinking water samples.
- Two isolates matched Yersinia proxima, a newly described species.
- One isolate belonged to a non-pathogenic clade of Yersinia enterocolitica.

## Abstract

Three Yersinia species were identified from samples of drinking water from diverse geographic regions of Ireland. Conventional commercial biochemical identification systems classified them as Yersinia enterocolitica. Since this organism is the most common cause of bacterial gastroenteritis in some countries, further investigation was warranted. The aim of the study was to provide a microbial characterisation of three Yersinia species, to determine their pathogenicity, and to review the incidence rate of Yersinia enterocolitica detection in our region.

Organism identification was performed using conventional commercial diagnostic systems MALDI-TOF, API 20E, API 50CHE, TREK Sensititre GNID and Vitek 2 GN, and whole genome sequencing (WGS) was performed. Historical data for detections was extracted from the lab system for 2008 to 2023.

All three isolates gave “good” identifications of Yersinia enterocolitica on conventional systems. Further analysis by WGS matched two of the isolates with recently described Yersinia proxima, and the third was a member of the non-pathogenic Yersinia enterocolitica clade 1Aa.

Our analysis of these three isolates deemed them to be Yersinia species not known currently to be pathogenic, but determining this necessitated the use of next-generation sequencing and advanced bioinformatics. Our work highlights the importance of having this technology available to public laboratories, either locally or in a national reference laboratory. The introduction of molecular technologies for the detection of Yersinia species may increase the rate of detections. Accurate identification of significant pathogens in environmental, public health and clinical microbiology laboratories is critically important for the protection of society.

The online version contains supplementary material available at 10.1007/s11845-024-03641-5.