Table 1.

Breakpoints used for AST testing of E. coli and Salmonella spp. isolates.

Antimicrobial class	Antimicrobial agent	Range (μg/ml)	ECOFFa		CLSIb or NARMSc
			E. coli	Salmonella spp.	S	I	R
Aminoglycosides	Gentamicin	0.25–16	2	2	≤ 4	8	≥16
	Streptomycin	2–64	16	16	≤ 32	–	> 32
β-lactam / β-lactam inhibitor combinations	Amoxicillin-clavulanate	1–32	–d	–	≤ 8	16	≥32
Cephems	Cefoxitin	0.5–32	8	8	≤ 8	16	≥32
	Ceftiofur	0.12–8	1	2	≤ 2 e	4	≥8
	Ceftriaxone	0.25–64	0.12	–	≤ 1	2	≥4
Fluoroquinolones	Ciprofloxacin (E. coli)	0.015–4	0.06	0.06	≤ 1	2	≥4
	Ciprofloxacin (Salmonella spp.)	0.015–4	0.06	0.06	≤ 0.06	0.12–0.5	≥1
Folate pathway inhibitors	Trimethoprim-sulfamethoxazole	0.12–4	1	1	≤ 2	–	≥4
Penicillins	Ampicillin	1–32	8	8	≤ 8	16	≥32
Phenicols	Chloramphenicol	2–32	16	16	≤ 8	16	≥32
Tetracyclines	Tetracycline	4–32	8	8	≤ 4	8	≥16

^aEUCAST epidemiological cut-off values (μg/ml).

^bCLSI VET01S, or M100S breakpoints (μg/ml), S = sensitive; I = intermediate; R = resistant.

^cNARMS breakpoints (μg/ml) (in blue).

^dnot defined.

^eE. coli only.