A new study from the University of Veterinary Medicine in Vienna has provided one of the most detailed portraits yet of haemolytic uropathogenic Escherichia coli circulating in companion animals. By analysing 51 haemolytic E. coli isolates recovered from the urine of dogs and cats with signs of urinary tract infections between 2017 and 2023, researchers at the Institute for Microbiology have mapped the virulence gene repertoire, phylogenetic background, clonal structure and antimicrobial susceptibility of these bacteria. The findings, published in Veterinary Medicine and Science, carry implications not only for veterinary practice but also for public health, given the close contact people share with their pets.
Urinary tract infections are among the most frequently diagnosed infectious diseases in dogs, and uropathogenic E. coli, commonly abbreviated UPEC, causes the majority of these infections in both humans and animals. UPEC belongs to the broader family of extraintestinal pathogenic E. coli, or ExPEC, a group of strains that also includes avian pathogenic and sepsis-associated subpathotypes. What distinguishes UPEC is a toolkit of virulence factors that allows the bacterium to colonise and proliferate on the epithelial cells lining the bladder. Chief among these are fimbrial adhesins, particularly Type 1 fimbriae, extracellular protein appendages that anchor the bacteria to bladder cells and initiate infection.
The defining feature of the isolates in this study was their haemolytic activity, the ability to lyse red blood cells on sheep blood agar. That trait is driven by alpha-haemolysin, encoded by the hlyCABD operon. Alpha-haemolysin is a pore-forming toxin that inserts itself into target cell membranes, creating transmembrane pores whose dimensions and conductance properties have been fully characterised through decades of biochemical and structural work. The loss of membrane integrity causes the target cell to burst. In human medicine, roughly half of all UPEC strains carry the hlyA gene, but that proportion climbs with disease severity, reaching up to 78 percent in cases of pyelonephritis, a serious infection of the kidney. Previous work in companion animals has also linked hlyA genes to urinary infections in dogs and cats.
The Vienna team collected isolates from 32 dogs and 19 cats, most of which presented with cystitis, haematuria or dysuria. After recultivating the bacteria on 5 percent sheep blood agar, the researchers extracted DNA and deployed a custom-made DNA microarray platform to screen for a wide panel of virulence-associated genes. They also phylotyped the isolates using the quadruplex Clermont assignment method, determined clonal groups through two-locus CH-clonotyping based on the fumC and fimH sequences, and performed antimicrobial susceptibility testing by agar disc diffusion against fourteen antibiotic agents, following Clinical and Laboratory Standards Institute protocols.
The genetic picture that emerged was strikingly uniform. Fifty of the 51 isolates belonged to phylogenetic group B2, the lineage most commonly associated with extraintestinal pathogenic E. coli in both humans and animals; only a single isolate fell into group B1. Every single isolate carried both fimH, the adhesion gene regarded as a major UPEC virulence marker, and hlyA, the haemolysin gene. Nearly all isolates, 50 of 51, also carried cnf1, a toxin-encoding gene that codes for cytotoxic necrotising factor 1. Additional virulence factors appeared frequently but not universally: pic, which encodes a serine protease, was found in 15 isolates, while papC, part of the P-fimbriae apparatus, and iucD, an aerobactin synthesis gene found only in virulent strains, each appeared in 11 isolates, always occurring together.
The authors note that while the predominance of phylogroup B2 was expected, the complete conservation of the cnf1 and hlyA linkage within this geographic cohort offers novel insight into the regional clonal stability of UPEC in Austrian companion animals. Clonotyping differentiated 34 distinct CH clonotypes, with CH103-9 the most prevalent, accounting for seven isolates. Several other clonotypes appeared in pairs, suggesting limited clonal relatedness among the sampled animals. Notably, most of the detected clonotypes correspond to clonal complexes previously reported in UPEC studies elsewhere, including CC73, CC12, CC127, CC141 and CC372, the last of which has been primarily associated with dogs rather than humans.
Antimicrobial resistance proved to be rare. Forty-five of the 51 isolates, or about 88 percent, were susceptible to every antibiotic tested, a reassuring result for clinicians managing urinary infections in pets. Resistance, where it occurred, was well explained by the genotype. Detected resistance genes including blaTEM, blaOXA-2, sul1, sul2, dfrA1, dfrA5, tet(A), aac(3′)-IVa and catA matched the phenotypic findings, and four isolates displayed multidrug-resistant profiles.
One isolate, however, stood out as a cause for vigilance. This strain carried an extended-spectrum beta-lactamase phenotype and was resistant to beta-lactams, ciprofloxacin, tetracycline, gentamicin and fosfomycin. Sequencing of the quinolone resistance-determining regions revealed classic amino acid substitutions in gyrA and parC that explain the fluoroquinolone resistance. Genotypically, the isolate proved to belong to phylogroup B2, serogroup O25b, sequence type ST131 and clonotype CH40-30, and it carried both blaCTX-M-15 and blaOXA-2. The B2-O25b-ST131 clone is recognised as a major human-associated high-risk pandemic pathogen responsible for a wide range of infections worldwide. Its sporadic detection in Austrian animals, from wildlife, canine prostate tissue, porcine intestinal samples and most recently a faecal sample, had been documented before, but this is a noteworthy addition from a companion animal with a urinary infection.
The study has limitations the authors acknowledge candidly. By restricting the analysis to haemolytic isolates, the work introduces selection bias, and the virulence and resistance potential of non-haemolytic strains causing urinary infections remains to be investigated. The virulence gene panel, while extensive, was finite, and the researchers suggest that whole-genome sequencing of a larger strain collection would provide an even more comprehensive characterisation. The low number of resistant isolates also limits broader epidemiological conclusions about antimicrobial resistance in canine and feline urinary infections.
Nevertheless, the clinical message is broadly positive. The data indicate that a significant proportion of E. coli urinary tract infections in companion animals can still be successfully managed with existing antibiotic therapies. At the same time, the virulence potential of these strains poses a relevant concern for both public and animal health, and the risk of human infection or colonisation from pet-associated isolates has yet to be fully determined. The existence of multidrug-resistant strains in pets with zoonotic potential, exemplified by the ST131 finding, underscores, in the authors’ view, the critical need for a continuous One Health approach to monitor and control the virulence and antimicrobial resistance of E. coli at the interface between animals and people.
Subject of Research: Characterisation of haemolytic uropathogenic Escherichia coli isolated from dogs and cats with urinary tract infections
Article Title: Characterisation of Haemolytic Uropathogenic Escherichia coli Isolated From Dogs and Cats
Article References: Büttner, S., Spergser, J., Makarova, O., Szostak, M. P., Rosel, A. C., Ruppitsch, W., Schäfer‐Somi, S., Müller, E., Braun, S. D., Monecke, S., Ehricht, R., Künzel, F., & Loncaric, I. (2026). Characterisation of Haemolytic Uropathogenic Escherichia coli Isolated From Dogs and Cats. Veterinary Medicine and Science, 12(5), Article e71200. https://doi.org/10.1002/vms3.71200
Image Credits: AI Generated
DOI: 10.1002/vms3.71200
Keywords: uropathogenic E. coli, dogs, cats, urinary tract infections, alpha-haemolysin, virulence genes, phylogroup B2, ST131, antimicrobial resistance, ESBL, One Health, veterinary microbiology
Cite Scienmag News
APA
MLA
Chicago
Kristina Jarvis. (September 12, 2026). Haemolytic Uropathogenic E. coli in Dogs and Cats Reveals Distinct Virulence Patterns. Scienmag. https://scienmag.com/haemolytic-uropathogenic-e-coli-in-dogs-and-cats-reveals-distinct-virulence-patterns/
Kristina Jarvis. “Haemolytic Uropathogenic E. coli in Dogs and Cats Reveals Distinct Virulence Patterns.” Scienmag, 12 September 2026, https://scienmag.com/haemolytic-uropathogenic-e-coli-in-dogs-and-cats-reveals-distinct-virulence-patterns/. Accessed 12 September 2026.
Kristina Jarvis. “Haemolytic Uropathogenic E. coli in Dogs and Cats Reveals Distinct Virulence Patterns.” Scienmag. September 12, 2026. https://scienmag.com/haemolytic-uropathogenic-e-coli-in-dogs-and-cats-reveals-distinct-virulence-patterns/
Copy citation
Download RIS
Tags: alpha-haemolysinAntimicrobial Resistanceantimicrobial susceptibility of UPECcanine urinary tract infectionscatsclonal structure of uropathogenic bacteriadogsESBLExPEC strains in companion animalsfeline urinary tract infectionshaemolytic E. coli virulence factorsOne Healthphylogenetic analysis of pathogenic E. coliphylogroup B2public health implications of pet-associated E. coli infectionsST131urinary tract infectionsuropathogenic E. coliUropathogenic E. coli in dogs and catsveterinary infectious disease researchveterinary microbiologyvirulence gene profiling in veterinary microbiologyvirulence geneszoonotic potential of uropathogenic bacteria
