# Sudden deaths of two dogs in a breeding colony associated with enteropathogenic Escherichia coli and necrotoxigenic Escherichia coli

## TL;DR

Two young dogs suddenly died from a co-infection involving specific strains of Escherichia coli, revealed through whole-genome sequencing.

## Contribution

The use of whole-genome sequencing identified a novel co-infection involving EPEC and ExP-NTEC in sudden canine deaths.

## Key findings

- Whole-genome sequencing identified ST5683 and ST127 E. coli strains with distinct virulence factors in deceased pups.
- Post-mortem findings included bronchopneumonia, hepatic lipidosis, and gastrointestinal inflammation linked to the E. coli co-infection.
- The cases highlight the importance of advanced diagnostics like WGS in understanding complex E. coli infections in neonatal dogs.

## Abstract

This case report describes the peracute deaths of two healthy pups in a breeding facility associated with enteropathogenic Escherichia coli (EPEC) and a distinct strain of necrotoxigenic E. coli (ExP-NTEC) co-infection. When E. coli is recovered from post-mortem samples, the role of the organism can be challenging to elucidate. In this case, the use of whole-genome sequencing (WGS) uncovered the virulence factors associated with isolates from both cases and a molecular epidemiological connection between the two deaths.

A 7-week-old male and an 8-week-old female intact mixed-breed dogs were found deceased, shortly after routine examination with no preceding clinical signs. Post-mortem examination revealed multiple organ abnormalities, including bronchopneumonia with alveolar collapse, hepatic lipidosis, gastrointestinal inflammation, and bacterial colonization in the lungs and intestines. Bacterial cultures from the lungs and intestines of both pups yielded multiple bacterial species. WGS of six E. coli isolates from both pups identified ST5683 and ST127 strains, possessing two different morphotypes and virulence factors that distinguished them as EPEC ExP-NTEC.

The findings suggest a role of EPEC and ExP-NTEC in the sudden deaths of neonatal dogs, possibly exacerbated by a naïve immune system. It is challenging to fully characterize the pathogenesis and potential risk factors as E. coli is present in the gastrointestinal system of healthy and asymptomatic carrier animals; however, these cases highlight the importance of comprehensive diagnostic approaches, including tools such as WGS.