Diversity of <i>Escherichia coli</i> from Faecal Samples of Danish Calves with Diarrhoea

• Published in: Veterinary Sciences
• Main Authors: Anna Luiza Farias Alencar, Abdurrahman Hassan Jibril, Birgitta Svensmark, Lene Agerskov, Henrik Læssøe Martin, Marc Stegger, André Becker Saidenberg, Gang Liu, Yaovi Mahuton Gildas Hounmanou, Annette Sønderholm Juel, John Elmerdahl Olsen, Rikke Heidemann Olsen
• Format: Article
• Language: English
• Published: MDPI AG 2025-10-01
• Subjects: calf diarrhoea; <i>Escherichia coli</i>; population diversity
• Online Access: https://www.mdpi.com/2306-7381/12/10/987

Several different pathogens, including <i>Escherichia coli</i>, are strongly associated with calf diarrhoea. The population diversity of intestinal <i>E. coli</i> within each diarrhetic calf and between diarrhetic calves is not well understood. In the present study, 391 faecal samples were obtained during 2023–2024 from Danish dairy calves with diarrhoea. Semi-quantified growth estimates of <i>E. coli</i> after culturing did not reflect the diarrhetic grade nor whether <i>E. coli</i> was the only pathogen observed in the sample. From each sample, five isolates were subjected to multiple-locus variable-number tandem repeat analysis (MLVA) and revealed that 70% of faecal samples contained more than one type of <i>E. coli.</i> Genotyping, sequence typing and in silico serotyping showed a large diversity of <i>E. coli</i> between faecal samples. Surprisingly, isolates with a genotype representing mixed features of Diffusely adhering <i>E. coli</i>/Extraintestinal pathogenic <i>E. coli</i> were found in 25% of the isolates, while the classic Enterotoxigenic <i>E. coli</i> genotype was only observed in 5% of the isolates, and only 4% of the faecal samples were positive for <i>E. coli</i> F5 (K99) fimbriae, as determined by PCR. In conclusion, a diverse population of (non-F5) <i>E. coli</i> is associated with diarrhoea in calves. High genomic diversity of <i>E. coli</i> within samples needs to be considered when selecting only one isolate for antimicrobial resistance profiling and vaccination measurements.