Table 1. Characterization of extended-spectrum β-lactamase-producing Escherichia coli (ESBLECs) and their antimicrobial resistance patterns.

Horse No.	Sampling location	β-lactamase genes	Antimicrobial resistance patterna	Phylogenetic group	Code of isolateb (n=24)
24	Mihod	blaCTX-M-2	ABPC, CEZ, CTX, SM, OTC, TC	A	ac
		blaTEM-1, blaCTX-M-2	ABPC, CEZ, CTX, SM, OTC, TC, TM	A	b
34	Miho	blaTEM-1, blaCTX-M-2	ABPC, CEZ, CTX, TM	B2	ac
		blaTEM-1, blaCTX-M-2	ABPC, CEZ, CTX, SM, TM	B2	b, c
39	Miho	blaTEM-1, blaCTX-M-2	ABPC, CEZ, CTX, SM, TM	B1	ac, b
47	Miho	blaCTX-M-2	ABPC, CEZ, CTX, SM, OTC, TC, TM	B1	ac, b
55	Miho	blaCTX-M-2	ABPC, CEZ, CTX	D	ac
		blaCTX-M-2	ABPC, CEZ, CTX, OTC, TC	D	b
68	Miho	blaCTX-M-2	ABPC, CEZ, CTX, TM	A	ac
78	Miho	blaCTX-M-2	ABPC, CEZ, CTX	B2	ac, b
107	Ritto	blaCTX-M-2	ABPC, CEZ, CTX, SM	B1	ac
116	Ritto	blaTEM-1, blaCTX-M-2	ABPC, CEZ, CTX, SM, TM	B2	ac, b
		blaTEM-1, blaCTX-M-2	ABPC, CEZ, CTX, TM	B2	c
130	Ritto	blaCTX-M-2	ABPC, CEZ, CTX, SM, TM	A	ac, b
131	Ritto	blaCTX-M-2	ABPC, CEZ, CTX	B2	ac
		blaCTX-M-2	ABPC, CEZ, CTX, OTC, TC	B1	bc
144	Ritto	blaCTX-M-2	ABPC, CEZ, CTX, SM, TM	B1	ac, b

^aABPC, ampicillin; CEZ, cefazolin; CTX, cefotaxime; SM, streptomycin; TC, tetracycline; OTC, oxytetracycline; TM, trimethoprim. Antimicrobial suscaptibility test was interpreted using CLSI criteria and JVARM report. ^bOne or more isolates were confirmed as ESBLEC from one sample. ^cThirteen selected donor isolates in conjugation assay; donor isolate per sample was considered based on phylogenetic group analysis. ^dMiho, Miho Training Center, Japan Racing Association, Ibaraki; Ritto, Ritto Training Center, Japan Racing Association, Shiga.