A One Health approach, defined as an approach to health that considers the close connections between humans, animals, and the environment, is key to reducing the spread of antibiotic-resistant bacteria (ARB). Research on the reservoirs of ARB has focused mainly on human medical hospitals and the livestock industry. The potential health risks posed by dogs and cats as a reservoir for ARB has been largely overlooked, despite the intimate contact between pet owners and their pets. The aim of this dissertation was to contribute to filling major scientific gaps on how companion animal veterinarians make decisions about antibiotics, the role that pets and residential locations play in human infections caused by ARB, and the ways in which ARB that affect human health may spread in veterinary hospitals. In the first study, we conducted in-depth interviews with veterinarians about how they make decisions on antibiotic use. We found that financial barriers are a significant driver behind antibiotic decision-making. Veterinarians perceived finances to affect issues including the use and selection of diagnostic tests that are used to guide antibiotic use, which antibiotics are stocked in practice pharmacies, and the use of inappropriate prescribing as an attempt to avoid economic euthanasia. In the second study, we identified geographic locations where high concentrations of children and dogs with ARB lived. We found that while residential location is a risk factor for ampicillin-resistant Escherichia coli, locations of higher and lower risk were different between children and dogs. Children living in more urban areas were at greater risk but living in the same area conferred a lower risk to dogs. In the third study, we investigated risk factors associated with the acquisition of a blaNDM-5 carbapenem resistant E. coli strain, as part of an outbreak investigation at a veterinary hospital. Using a case-control study design, we found that patients exposed to endotracheal intubation, surgery, and anesthesia were at greater risk. These studies will serve as a starting point for future research on the impact of ARB in companion animals and provide baseline data that will inform antibiotic stewardship interventions in veterinary medicine.