Extended spectrum beta-lactamase (ESBL)-producing Escherichia coli are an emerging problem in veterinary and human medicine. Our study concentrated on the estimation of the prevalence and factors associated with the carriage of ESBL-producing E. coli in dogs who visited a veterinary clinic in northern Germany in 2017. For this reason, 1000 patients (healthy and sick dogs) were tested, resulting in 1000 samples originating from rectal swabs. Additional data were collected using a self-reported questionnaire that was completed by the dog owner. Factors associated with ESBL carriage were considered for further modeling if p < 0.05 using a two-sided Fisher test. Using a backward elimination procedure, the variables for the final multivariable logistic regression model were identified. In total, 8.9% of the dogs tested were positive for carriage of ESBL-producing E. coli. Seven factors were associated with the colonization of dogs with ESBL-E. coli within the multivariable model, namely husbandry system (p = 0.0019, OR = 3.00; 95% CI: 1.50–6.00), contact with puppies (p = 0.0044, OR = 2.43; 95% CI: 1.32–4.46), feeding of raw meat (p = 0.011, OR = 2.28; 95% CI: 1.21–4.31), food residues (p = 0.0151, OR = 2.31; 95% CI: 1.18–4.53) and food supplements (p = 0.0487, OR = 0.426; 95% CI: 0.18–0.96), and antibiotic treatments of dogs (p = 0.0005, OR = 3.030; 95% CI: 1.62–5.68) or owners (p = 0.041, OR = 2.74; 95% CI: 1.04–7.19) prior to the study. These factors refer to the animals themselves as well as to the owners and their habits or medical treatments. Although the causality and direction of transmission from owners to their dogs cannot be proven, the factor of antibiotic treatment of the owner is clearly associated with the dog’s status.

Antimicrobial resistance (AMR) is a growing concern in veterinary and public health, with extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli playing a significant role. This study examined 1,000 healthy and sick dogs from a veterinary clinic in northern Germany and identified 85 ESBL-producing E. coli . Whole-genome sequencing of these isolates revealed seven phylogroups. A (38.8%) and B1 (32.9%) were the most common. Multilocus sequence typing identified 42 sequence types (STs), with the globally occurring lineages ST744 and ST10 being predominant. Single nucleotide polymorphism analysis showed the clonal circulation of ST744 among dogs in shared environments, such as households or breeders, whereas ST10 isolates displayed greater genetic diversity. ST131, a pathogenic international high-risk clonal lineage often associated with humans, was assigned to one isolate. Virulence-associated genes (VAGs) were abundant across the isolates, with siderophore systems, biofilm formation, and adherence traits being prominent. All isolates carried enterobactin genes with additional siderophore systems, such as yersiniabactin and aerobactin, present in 36 isolates. The highest number of VAGs (25) was observed in isolates belonging to the pathogenic lineages ST648 and ST405. Sixty-nine percent of the isolates were multidrug-resistant, carrying resistance genes for three or more antibiotic classes, with beta-lactam, aminoglycoside, and tetracycline resistance being the most frequent. This study highlights globally occurring E. coli lineages in companion animals and the role of close contact environments in their dissemination. Although dog-to-human transmission was not investigated in this study, these findings support the need for a One Health approach to address AMR, emphasizing the interconnected health of humans, animals, and the environment. IMPORTANCE: This study demonstrated the presence of globally significant Escherichia coli lineages in dogs and highlighted the impact of close-contact environments, such as households and breeders, on their spread. Many of the isolates exhibited genetic multidrug resistance and virulence features, posing challenges for effective treatment and control. These findings emphasize the interconnected nature of human, animal, and environmental health, underlining the need for a One Health approach to address antimicrobial resistance.