Pathotypes and drug susceptibility of Escherichia coli isolated from companion dogs in Japan

Considering the possibility that Escherichia coli held by conpanion dogs could invade owners and human society, we investigated their pathogenicity and drug resistance. E. coli was isolated from stool samples of companion dogs (n=90) to examine O-serogroup, virulence genes, and drug susceptibility. The dogs were 4 months to 16 years old, and were mainly treated with cefalexin, enrofloxacin, or amoxicillin.A total of 69 samples were positive for E. coli (76% of examined dogs), and the most common O-serogroup was O18 (n=13). Nine diarrheagenic E. coli, including enteropathogenic E. coli (n=3), enteroaggregative E. coli (n=1), and astA-carrying E. coli (n=5), were isolated. We also isolated a total of 28 E. coli that were resistant to at least one of the six antimicrobials, including cephalothin (CET), ceftazidime (CAZ), cefotaxime (CTX), chloramphenicol (CP), fosfomycin (FOM), and norfloxacin (NLFX). The resistance pattern was as follows: CET, n=16; NLFX, n=3; CET/CP (resistance to both CET and CP), n=1; CET/NLFX, n=1; CET/CAZ/CTX, n=3; CET/CTX/NLFX, n=2; CET/CP/NLFX, n=1; and CET/CAZ/CTX/NLFX, n=1. Moreover, a total of ten E. coli isolates were found to produce extended-spectrum beta-lactamase (ESBL), including AmpC (n=4OUT, O18, O74 and O166), CTX-M-1 (n=1; O25), CTX-M-9 (n=4; OUT, O18, O18 and O125), and AmpC/CTX-M-9 (n=1; OUT) groups. The AmpC-producing E. coli strains included enteropathogenic E. coli and carried astA. Because diarrheagenic E. coli or E. coli with affinity for human were isolated from some dogs and some of them were found to have ESBL, in future, it would be necessary to investigate for these transmission and expanding to humans.