Livestock as possible reservoir of Escherichia albertii in Switzerland

Escherichia albertii is an emerging zoonotic foodborne pathogen. Its prevalence, distribution, and reservoirs are not yet clearly defined. In this study, we evaluated the occurrence and genomic characteristics of E. albertii in livestock from Switzerland. A total of 515 caecal samples from sheep, cattle, calves, and fattening swine were collected between May 2022 and August 2022 at abattoir level. Using an E. albertii-specific PCR targeting the Eacdt-gene, 23,7 % (51/215) of swine from 24 different farms were positive. One (1 %) out of 100 calves showed a positive PCR result, while all samples from sheep and cattle were PCR negative. Eight E. albertii isolates could be recovered from swine samples and were analysed using whole-genome sequencing. All eight isolates belonged to ST2087 or a ST4619 group subclade, as did most genomes of the 11 available global swine isolates from public databases. These two clusters shared the presence of a virulence plasmid harboring the sitABCD and iuc genes. In summary, we demonstrate that fattening swine constitute an E. albertii reservoir in Switzerland and describe specific swine-associated lineages.