Molecular ecology and risk factors for third-generation cephalosporin-resistant Escherichia coli carriage by dogs living in urban and nearby rural settings. Third generation cephalosporin resistant E. coli from dogs

Third-generation cephalosporin-resistant (3GC-R) Escherichia coli isolates were compared from dogs living in a city and in a rural area ∼30 km away, and to those from cattle and humans in these regions. Risk factors associated with 3GC-R E. coli carriage in these two cohorts of dogs were also determined. Faecal samples from a total of 600 dogs were processed to recover 3GC-R E. coli using 2 mg/L cefotaxime. WGS was by Illumina and risk factor analyses were by multivariable linear regression using the results of an owner-completed survey. 3GC-R E. coli were excreted by 20/303 rural and 31/297 urban dogs. The dominant canine 3GC-R ST was ST963 (blaCMY-2), which also accounted for 25% of CMY-2-producing E. coli in humans. Phylogenetic overlap between cattle and rural dog CTX-M-14-producing E. coli ST117 was observed as well as acquisition of pMOO-32-positive E. coli ST10 by a rural dog, a plasmid common on cattle farms in the area. Feeding raw meat was associated with carrying 3GC-R E. coli in rural dogs, but not in urban dogs, where swimming in rivers was a weak risk factor. To conclude, we show clear zoonotic potential for resistant canine E. coli, our work suggests interventions that may reduce this threat. In rural dogs, carriage of 3GC-R E. coli, particularly CTX-M producers, was phylogenetically associated with interaction with local cattle and epidemiologically associated with feeding raw meat. In urban dogs, sources of 3GC-R E. coli appear to be more varied and include environments such as rivers.