Table 3.

MIC_50, MIC₉₀, range and percent of P. multocida and M. haemolytica isolates collected from high-risk beef stocker calves prior to and 14 d after administration of saline susceptible to 12 antimicrobials at the time of arrival processing

		Pasteurella multocida				Mannheimia haemolytica
Antimicrobial	Sampling occasion	MIC50 (μg/mL)	MIC90 (μg/mL)	Range (μg/mL)	% Susceptible	MIC50 (μg/mL)	MIC90 (μg/mL)	Range (μg/mL)	% Susceptible
Ampicillin	1	≤0.25	≤0.25	≤0.25	N/A	N/A	N/A	N/A	N/A
	2	≤0.25	≤0.25	≤0.25	N/A	≤0.25	0.5	≤0.25 to 0.5	N/A
Ceftiofur	1	≤0.25	≤0.25	≤0.25	100	N/A	N/A	N/A	N/A
	2	≤0.25	≤0.25	≤0.25	100	≤0.25	2	≤0.25 to 2	100
Chlortetracycline	1	≤0.5	2	≤0.5 to 2	N/A	N/A	N/A	N/A	N/A
	2	≤0.5	2	≤0.5 to 8	N/A	>8	>8	0.5 to >8	N/A
Danofloxacin	1	≤0.125	≤0.125	≤0.125	100	N/A	N/A	N/A	N/A
	2	≤0.125	≤0.125	≤0.125	100	≤0.125	>1	≤0.125 to >1	86
Enrofloxacin	1	≤0.125	≤0.125	≤0.125	100	N/A	N/A	N/A	N/A
	2	≤0.125	≤0.125	≤0.125	100	≤0.125	>2	≤0.125 to >2	86
Florfenicol	1	0.5	1	0.25 to 1	100	N/A	N/A	N/A	N/A
	2	0.5	1	0.25 to 1	100	1	>8	≤0.25 to >8	86
Oxytetracycline	1	≤0.5	4	≤0.5 to 8	93	N/A	N/A	N/A	N/A
	2	≤0.5	8	≤0.5 to >8	80	>8	>8	0.5 to >8	46
Penicillin	1	≤ 0.125	0.25	≤ 0.125 to 0.25	100	N/A	N/A	N/A	N/A
	2	≤ 0.125	0.25	≤ 0.125 to 0.25	100	0.5	1	≤0.125 to 1	50
Spectinomycin	1	16	32	8 to >64	93	N/A	N/A	N/A	N/A
	2	16	>64	8 to >64	83	32	>64	≤8 to >64	86
Tilmicosin	1	≤4	32	≤4 to >64	93	N/A	N/A	N/A	N/A
	2	≤4	64	≤4 to >64	86	8	>64	8 to >64	79
Tulathromycin	1	≤1	32	1 to >64	93	N/A	N/A	N/A	N/A
	2	≤1	>64	1 to >64	86	8	>64	≤1 to >64	86
Tylosin	1	16	>32	8 to >32	N/A	N/A	N/A	N/A	N/A
	2	16	>32	16 to >32	N/A	>32	>32	8 to >32	N/A

N/A—breakpoints not available or too few isolates to summarize.