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.
