Table 4.

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

		Pasteurella multocida
Antimicrobial	Sampling occasion	MIC50 (μg/mL)	MIC90 (μg/mL)	Range (μg/mL)	% Susceptible
Ampicillin	1	≤0.25	≤0.25	≤0.25	N/A
	2	≤0.25	≤0.25	≤0.25	N/A
Ceftiofur	1	≤0.25	≤0.25	≤0.25	100
	2	≤0.25	≤0.25	≤0.25	100
Chlortetracycline	1	≤0.5	>8	≤0.5 to >8	N/A
	2	2	>8	≤0.5 to 8	N/A
Danofloxacin	1	≤0.125	≤0.125	≤0.125	100
	2	≤0.125	≤0.125	≤0.125	100
Enrofloxacin	1	≤0.125	≤0.25	≤0.125 to 0.25	100
	2	≤0.125	≤0.125	≤0.125	100
Florfenicol	1	0.5	1	≤0.25 to 1	100
	2	1	1	≤0.25 to 1	100
Oxytetracycline	1	≤0.5	>8	≤0.5 to >8	90
	2	1	>8	≤0.5 to >8	60
Penicillin	1	≤ 0.125	0.25	≤ 0.125 to 0.25	100
	2	0.25	0.5	≤ 0.125 to 0.5	80
Spectinomycin	1	16	>64	8 to >64	90
	2	16	>64	8 to >64	60
Tilmicosin	1	≤4	>64	≤4 to >64	90
	2	8	>64	≤4 to >64	60
Tulathromycin	1	≤1	>64	≤1 to >64	90
	2	4	>64	≤1 to >64	60
Tylosin	1	16	>32	8 to >32	N/A
	2	16	>32	16 to >32	N/A

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