Table 1.

Copy numbers of bla_CMY−2 and MICs of various antimicrobials for S. Typhimurium L-3553 and the spontaneous mutants selected on CTX-containing plates.

Strain	CTX concentration for selection (mg/L)	blaCMY−2 copy no.	MIC (mg/L)a							Approx. size of plasmid (kb)b
			CTX	CRO	CAZ	FOX	CHL	STR	OTC
L-3553	Not applicable	1.0	8	8	32	16	64	256	128	130
12-1	12.5	16.5	64	128	256	128	256	512	128	130
12-2	12.5	16.5	32	128	256	128	256	512	128	130
12-3	12.5	16.8	32	64	256	128	256	512	128	130
12-4	12.5	15.3	32	128	256	128	256	512	128	130
12-5	12.5	13.8	64	64	256	128	256	>512	128	130
12-6	12.5	15.8	32	128	256	128	256	>512	128	130
12-7	12.5	15.5	32	128	256	128	256	512	128	130
12-8	12.5	15.7	64	128	256	128	256	>512	128	130
12-9	12.5	17.4	64	64	256	128	256	>512	128	130
12-10	12.5	15.9	32	64	128	128	256	512	128	130
12-11	12.5	25.7	64	64	256	128	256	512	128	255, 390, 510, 640
12-12	12.5	24.5	64	128	256	128	256	512	128	255, 390, 510, 640
12-13	12.5	18.5	64	128	256	128	256	512	128	255, 390, 510, 640
12-14	12.5	25.7	64	128	256	128	256	512	128	255, 390, 510, 640
12-15	12.5	7.1	64	128	256	128	128	256	128	130, 255
12-16	12.5	14.9	32	64	256	128	256	512	128	130
12-17	12.5	21.7	64	128	256	128	256	512	128	255, 390, 510, 640
12-18	12.5	21.8	64	128	256	128	256	512	128	255, 390, 510, 640
12-19	12.5	5.9	64	128	256	128	256	512	128	130
12-20	12.5	17.3	32	64	256	128	256	>512	128	130
25-4	25	11.1	128	256	>512	128	256	>512	128	320, 430
25-5	25	15.4	128	256	>512	512	256	>512	256	130
25-6	25	85.3	64	128	512	256	256	512	128	510
25-7	25	17.1	128	256	>512	512	256	>512	256	130
25-8	25	67.4	64	128	512	256	256	512	128	440
25-9	25	18.8	128	256	>512	256	256	>512	256	130
25-10	25	12.9	128	256	512	256	256	>512	256	130
25-11	25	9.0	128	256	512	512	64	128	256	130
25-12	25	12.1	128	256	>512	512	256	>512	256	130
25-13	25	12.0	128	256	512	256	256	>512	128	130
25-14	25	15.9	64	128	512	128	256	>512	128	130
25-15	25	44.8	128	256	512	512	256	512	256	320, 390, 475, 560
25-16	25	13.1	128	256	>512	512	64	>512	128	130, 340, 440
25-17	25	34.1	128	128	512	128	256	>512	128	185, 250, 375, 495, 620
25-18	25	9.3	128	128	512	256	256	>512	256	130, 640
25-19	25	13.6	128	128	512	256	256	>512	128	130, 640
25-20	25	33.2	128	256	>512	512	256	>512	256	510, 570, 640
25-21	25	12.7	128	256	>512	256	256	>512	128	130
25-22	25	33.4	128	256	512	256	256	256	128	390, 475, 560, 640
25-23	25	12.8	128	256	>512	512	256	>512	128	130, 640

^aCTX, cefotaxime; CRO, ceftriaxone; CAZ, ceftazidime; FOX, cefoxitin; CHL, chloramphenicol; STR, streptomycin; OTC, oxytetracycline.

^bPlasmid size was estimated by PFGE after S1 nuclease digestion.