| Summary: | Overall, 836 <i>Escherichia coli</i> isolates (695 isolates from dogs and 141 from cats) were recovered from the diarrhea, skin/ear, urine, and genitals of dogs and cats between 2018 and 2019. Cefovecin and enrofloxacin resistance were noted in 17.1% and 21.2% of <i>E. coli</i> isolates, respectively. The cefovecin and enrofloxacin resistance rates were higher in dog isolates (18.1% and 22.9%) compared with the rates in cat isolates (12.1%, 12.8%). Interestingly, resistance to both antimicrobials was noted in 10.8% (90/836) of the isolates, predominantly in isolates from dogs. <i>bla</i><sub>CTX-M-14</sub>, <i>bla</i><sub>CTX-M-15</sub>, and <i>bla</i><sub>CMY-2</sub> were the most frequent extended-spectrum β-lactamase/plasmid-mediated AmpC β-lactamase (ESBL/AmpC)- gene types. The co-existence of <i>bla</i><sub>CTX-M and</sub><i>bla</i><sub>CMY-2</sub> was noted in six <i>E. coli</i> isolates from dogs. Sequencing analysis demonstrated that S83L and D87N in <i>gyrA</i> and S80I in <i>parC</i> were the most frequent point mutations in the quinolone resistance-determining regions of the cefovecin and enrofloxacin-resistant isolates. A total of 11 isolates from dogs carried the plasmid-mediated quinolone resistance genes (six <i>aac(6’)-Ib-cr</i>, four <i>qnrS</i>, and one <i>qnrB</i>), while only two cat isolates carried the <i>qnrS</i> gene. Multilocus sequence typing of the cefovecin and enrofloxacin-resistant isolates revealed that sequence type (ST)131 <i>E. coli</i> carrying <i>bla</i><sub>CTX-M-14</sub> and <i>bla</i><sub>CTX-M-15</sub> genes and ST405 <i>E. coli</i> carrying <i>bla</i><sub>CMY-2</sub> gene were predominant among the isolated <i>E. coli</i> strains. The majority of the ESBL/AmpC-producing isolates displayed diverse pulsed-field gel electrophoresis profiles. This study demonstrated that third-generation cephalosporin- and fluoroquinolone-resistant <i>E. coli</i> were widely distributed in companion animals. The detection of the pandemic ST131 clone carrying <i>bla</i><sub>CTX-M</sub>-<sub>14/15</sub> in companion animals presented a public health threat.
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