Table 1.

Characteristics of the three CMY-2-ST641 E. coli strains and their electroporants

Strains	MIC (μg/mL) of the donors				Gene location of blaCMY-2 in the original isolates	MIC (μg/mL) of the electroporants				Size of pColE1-like CMY from electroporants (bp)	Frequency of the first round of electroporation DH5α/DH10B	Frequency of the second round of electroporation DH5α/DH10B
	FOX	CIF	CTX	CAZ		FOX	CIF	CTX	CAZ
EC5106	128	16	4	16	Chromosome	64	32	16	32	14,845	10–8–10–9	10–2–10–3
EC6413	64	4	2	8	Chromosome	64	32	16	32	14,845	10–8–10–9	10–2–10–3
EC4103	64	4	2	8	Chromosome	64	32	16	32	14,845	10–8–10–9	10–2–10–3
DH5α/DH10B	–	–	–	–	–	2	0.125	0.03	0.03	–	–	–

Note: Electroporants were challenged for the electroporation by using recipients DH5α or DH10B.

Abbreviations: FOX, cefoxitin; CIF, ceftiofur; CTX, cefotaxime; CAZ, ceftazidime; MIC, minimal inhibitory concentration.