Page Banner

United States Department of Agriculture

Agricultural Research Service

Related Topics

NARMS -National Antimicrobial Resistance Monitoring System Animal Isolates
headline bar
1 - Overview
2 - Sampling and Testing Methods
3 - Antimicrobials Tested: Concentration Ranges and Breakpoints
4 - NARMS Data
Antimicrobials Tested: Concentration Ranges and Breakpoints

Breakpoints Used for Susceptibility Testing of Salmonella and E. coli1

 

 

Antimicrobial Concentration Range  (µg/ml)

Breakpoints (µg/ml)

CLSI Class2

Antimicrobial Agent

1997

1998

1999

2000

2001

2002-2003

2004-2010

2011-2012

Susceptible

Intermediate

Resistant

 

 Amikacin

4  -  32

4  -  32

4  -  32

4  -  32

4  -  32

0.5  -  4

0.5  -  64

NT

< 16

32

> 64

 Aminoglycosides

 Apramycin

2  -  16

2  -  16

2  -  32

2  -  32

2  -  32

NT

NT

NT

N/A

N/A

>32

 

 Gentamicin

0.25 -- 16

0.25 -- 16

0.25  -  16

0.25  -  16

0.25  -  16

0.25  -  16

0.25  -  16

0.25  -  16

< 4

8

> 16

 

 Kanamycin

16  -  64

16  -  64

16  -  64

16  -  64

16  -  64

8  -  64

8  -  64

8  -  64

< 16

32

> 64

 

 Streptomycin3

32  -  256

32  -  256

32  -  256

32  -  256

32  -  64

32  -  64

32  -  64

32  -  64

< 32

N/A

> 64

 β-Lactam/β-Lactamase
 Inhibitor Combinations

 Amoxicillin–          Clavulanic Acid

0.5/0.25  -  32/16

0.5/0.25  -  32/16

0.5/0.25  -  32/16

0.5/0.25  -  32/16

0.5/0.25  -  32/16

1/0.5  -  32/16

1/0.5  -  32/16

1/0.5  -  32/16

< 8 / 4

16/8

> 32 / 16

 Carbapenem

 Imipenem

NT

NT

NT

NT

0.25  -  8

NT

NT

NT

< 4

8

>16

 Carboxypenicillins

 Ticarcillin

2  -  128

2  -  128

NT

NT

NT

NT

NT

NT

< 16

32 - 64

>128

 Cephems

 Cephalothin

1 - 32

1 - 32

1 - 32

1 - 32

1 - 32

2 - 32

NT

NT

< 8

16

> 32

 

 Ceftiofur

0.5  -  16

0.5  -  16

0.5  -  16

0.5  -  16

0.5  -  16

0.12  -  8

0.12  -  8

0.12  -  8

< 2

4

> 8

 

 Cefoxitin

NT

NT

NT

4  -  32

4  -  32

0.5  -  16

0.5  -  32

0.5  -  32

≤ 8

16

> 32

 

 Ceftriaxone

0.25  -  16

0.25  -  16

0.25  -  64

0.25  -  64

0.25  -  64

0.25  -  64

0.25  -  64

0.25  -  64

1

2

4

 Folate Pathway Inhibitors

 Sulfonamides   Sulfamethoxazole: 1998-2003/Sulfizoxazole: 2004-2009

128  -  512

128  -  512

128  -  512

128  -  512

128  -  512

16  -  512

16  -  256

16  -  256

≤ 256

N/A

> 512

 

 Trimethoprim– Sulfamethoxazole

0.12/2.4 - 4/76

0.12/2.4 - 4/76

0.12/2.4 - 4/76

0.12/2.4 - 4/76

0.12/2.4 - 4/76

0.12/2.4 - 4/76

0.12/2.4 - 4/76

0.12/2.4 - 4/76

≤ 2 / 38

N/A

> 4 / 76

 Macrolide

 Azithromycin3

NT

NT

NT

NT

NT

NT

NT

0.12  -  16

N/A

N/A

N/A

 Penicillins

  Ampicillin

2  -  64

2  -  64

2  -  32

2  -  32

2  -  32

1  -  32

1  -  32

1  -  32

< 8

16

> 32

 Phenicols

 Chloramphenicol

4  -  32

4  -  32

4  -  32

4  -  32

4  -  32

2  -  32

2  -  32

2  -  32

  8

16

> 32

 Florfenicol

NT

NT

2  -  16

NT

NT

NT

NT

NT

N/A

N/A

N/A

 Quinolones

 Ciprofloxacin

0.015  -  2

0.015  -  2

0.015  -  4

0.015  -  4

0.015  -  4

0.015  -  4

0.015  -  4

0.015  -  4

≤ 0.06

0.12 -0.5

> 1

 

 Nalidixic acid

4  -  64

4  -  64

4  -  256

4  -  256

4  -  64

0.5  -  32

0.5  -  32

0.5  -  32

≤ 16

N/A

> 32

 Tetracyclines

 Tetracycline

4  -  64

4  -  64

4  -  32

4  -  32

8  - 16

4  -  32

4  -  32

4  -  32

≤ 4

8

> 16

Save as PDF

1Breakpoints established by CLSI (Clinical and Laboratory Standards Institute) were used when available
2According to CLSI M100 document
3There are no CLSI breakpoints for streptomycin

NT=Not tested
NA=Not applicable


Breakpoints Used for Susceptibility Testing of Campylobacter1

 

 Antimicrobial Agent

Antimicrobial Concentration Range  (µg/ml) 1998-2004

Breakpoints (µg/ml) Etest (1998-2004)

Antimicrobial Concentration Range  (µg/ml) 2005-2012

Breakpoints (µg/ml) Microbroth Dilution (2005-2011)

 

 

Susceptible

Intermediate

Resistant

Susceptible

Intermediate

Resistant

CLSI Subclass2

 Aminoglycosides

 Gentamicin

0.016 - 256

< 4

8

> 16

0.12 - 32

< 2

4

> 8

 Lincosamides

 Clindamycin

0.016 - 256

< 0.5

1 - 2

> 4

0.03 - 16

< 2

4

> 8

 Macrolides

 Azithromycin

0.016 - 256

< 0.25

0.5 - 1

> 2

0.015 - 64

< 2

4

> 8

 Erythromycin

0.016 - 256

< 0.5

1 - 4

> 8

0.03 - 64

< 8

16

> 32

 Ketolides

 Telithromycin

NT

NT

NT

NT

0.015 - 8

< 4

8

> 16

 Phenicols

 Florfenicol

NT

NT

NT

NT

0.03 - 64

< 4

N/A

N/A

 Chloramphenicol

0.016 - 256

< 8

16

> 32

NT

NT

NT

NT

 Fluoroquinolones

 Ciprofloxacin

0.002 - 32

< 1

2

> 4

0.015 - 64

< 1

2

> 4

 Quinolones

 Nalidixic acid

0.016 - 256

< 16

N/A

> 32

4 - 64

< 16

32

> 64

 Tetracyclines

 Tetracycline

0.016 - 256

< 4

8

> 16

0.06 - 64

< 4

8

> 16

Save as PDF

1Breakpoints established by CLSI (Clinical and Laboratory Standards Institute)were used when available. CLSI breakpoints are only available
for erythromycin, ciprofloxacin, and tetracycline
2According to CLSI M100 document

NT=Not tested
NA=Not applicable

Breakpoints Used for Susceptibility Testing of Enterococcus1

CLSI Subclass2

Antimicrobial Agent

Antimicrobial Concentration Range  (µg/ml)

Breakpoints  (µg/ml)

2003

2004-2005

2006-2008

2009-2012

Susceptible

Intermediate

Resistant

Aminoglycoside

Gentamicin

128 - 1024

128 - 1024

128 - 1024

128 - 1024

≤ 500

N/A

> 500

Kanamycin

128 - 1024

128 - 1024

128 - 1024

128 - 1024

≤ 512

N/A

> 1024

Streptomycin

512 - 2048

512 - 2048

512 - 2048

512 - 2048

≤ 1000

N/A

> 1000

Glycopeptide

Vancomycin

0.5-32

0.5 - 32

0.5 - 32

0.25 - 32

≤ 4

8 - 16

> 32

Glycylcycline

Tigecycline

NT

NT

0.015 - 0.5

0.015 - 0.5

≤ 0.25

N/A

N/A4

Ionophore coccidiostat

Salinomycin

1 - 32

NT

NT

NT

≤8

 -

≥16

Lincosamides

Lincomycin

1 - 32

1 - 32

1 - 32

1 - 8

≤ 2

4

≥ 8

Lipopeptide

Daptomycin

NT

0.5 - 16

0.5 - 16

0.25 - 16

≤ 4

N/A

N/A5

Macrolide

Erythromycin

0.5 - 8

0.5 - 8

0.5 - 8

0.25 - 8

≤ 0.5

1 - 4

≥ 8

Tylosin

0.25 - 32

0.25 - 32

0.25 - 32

0.25 - 32

≤ 8

16

≥32

Nitrofuran

Nitrofurantoin

2 - 128

2 - 128

2 - 64

2 - 64

≤ 32

64

≥128

Oxazolidinones

Linezolid

0.5 - 8

0.5 - 8

0.5  -  8

0.5 - 8

≤ 2

4

≥ 8

Penicillin

Penicillin

0.5 - 16

0.5 - 16

0.5 - 16

0.25 - 16

≤ 8

N/A

≥ 16

Phenicol

Chloramphenicol

2 - 32

2 - 32

2 - 32

2 - 32

≤ 8

16

≥ 32

Phosphoglycolipid

Flavomycin

1 - 32

1 - 32

1 - 16

NT

≤ 8

16

≥ 32

Polypeptide

Bacitracin

8 - 128

8 - 128

NT

NT

≤ 16

32

≥ 64

Quinolone

Ciprofloxacin

0.12 - 4

0.12 - 4

0.12 - 4

0.12 - 4

≤ 1

2

≥ 4

Streptogramin

Quinupristin/Dalfoprisitin

1 - 32

1 - 32

1 - 32

0.5 - 32

≤ 1

2

≥ 4

Tetracycline

Tetracycline

4 - 32

4 - 32

4 - 32

1 - 32

≤ 4

8

≥ 16

Save as PDF

1Breakpoints established by CLSI (Clinical and Laboratory Standards Institute)were used when available
2According to CLSI M100 document
3For the aminoglycosides, breakpoints refer to high-level aminoglycoside resistance
4For tigecycline, only a susceptible breakpoint (≤ 0.25 µg/ml) has been established
5For daptomycin, only a susceptible breakpoint (≤ 4 µg/ml) has been established

NT=Not tested
NA=Not applicable


<< Previous    1     2     [3]     4     Next >>

Last Modified: 6/3/2014
Footer Content Back to Top of Page