TABLE 2.

Mutations in the rpoB gene associated with rifampin resistance in R. equi^a

Originb	Country	Rifampin MIC (µg/ml)	Substitution
			Codonc	Amino acid exchange
Human	Thailand	8	509	Ser → Pro
Horse	United States	64	513	Gln → Leu
Horse	Germany, France	2–4	516	Asp → Val
Horse	France, United States	128–256	526	His → Asp
Horse	France	8	526	His → Asn
Human, in vitro	Thailand, NAd	≥256	526	His → Tyr
In vitro	NA	≥256	526	His → Arg
Horse	France, United States	8–128	531	Ser → Leu
Horse	United States	≥256	531	Ser → Phe
Human	Thailand	64	531	Ser → Trp

^a Adapted from references 32, 42, 43.

^b Species of origin or in vitro mutations generated in the laboratory.

^c E. coli numbering.

^d NA: not applicable.