The aim of this study is to investigate the prevalence and carriage of Extended Spec - trum Beta-Lactamase (ESBL) and AmpC- producing strains of E. coli and Klebsi - ella spp in hospitalized dogs treated with antimicrobials. Tissue and fecal samples from 66 dogs were analyzed for presence of AmpC or ESBL producing bacteria. The dogs had to have been admitted to the surgical ward for at least 24 hours and have received antimicrobial treatment. Samples were plated onto bovine blood agar and after incubation for 24 + 24 h, five colonies morphologically consistent with E.coli and Klebsiella spp , were selected and recultured onto media containing antimicrobials. Dogs carrying ESBL/AmpC- producing bacteria were retested for rectal colonisation at 3-6 months intervals for up to 16 months. Five (7.6%) dogs carried bacterial strains posi - tive for ESBL/AmpC- producing- genes in feces. All tissue samples were negative. One dog, previously positive for bla CMY-2 , carried ESBL genotype bla TEM-52 , in the second sample. Four dogs remained posi - tive throughout the testing. None of the dogs had signs of infection or symptoms associ - ated with the carriage of ESBL or plasmid mediated-AmpC- producing bacteria. Seven unique MLVA-types were identified. The results from this study show fecal car - riage for as long as 16 months of ESBL/ AmpC- producing E.coli in dogs treated with antimicrobials. Although clonal spread could not be verified in this study, the risk of dissemination of multiresistant bacteria in animal hospitals and in the community must be considered
