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Volume 8, Number 12—December 2002

Research

Antimicrobial Resistance of Escherichia coli O26, O103, O111, O128, and O145 from Animals and Humans

Carl M. Schroeder*, Jianghong Meng*, Shaohua Zhao†, Chitrita DebRoy‡, Jocelyn Torcolini‡, Cuiwei Zhao*, Patrick F. McDermott†, David D. Wagner†, Robert D. Walker†, and David G. White†
Author affiliations: *University of Maryland, College Park, Maryland, USA; †U.S. Food and Drug Administration, Laurel, Maryland, USA; ‡The Pennsylvania State University, University Park, Pennsylvania, USA

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Table 2

Class, dilution range, and resistant breakpoints of tested antimicrobialsa

Class or antimicrobial Dilution range tested (µg/mL) NCCLS resistance breakpoint (µg/mL)
Cephalosporins    
   Cefoxitin 1–32 32
   Ceftiofur 1–16 8b
   Ceftriaxone 0.06–64 64
   Cephalothin 1–32 32
Penicillins    
   Amoxicillin-clavulanic acid 0.25/0.12–32/16 32/16
   Ampicillin 0.25–32 32
Sulfonamides and potentiated sulfonamides    
   Sulfamethoxazole 32–512 512
   Trimethoprim-sulfamethoxazole 0.06/1.19–4/76 4/76
Phenicols    
   Chloramphenicol 1–32 32
Quinolones and fluoroquinolones    
   Ciprofloxacin 0.004–8 4
   Nalidixic acid 2–256 32
Aminoglycosides    
   Gentamicin 0.25–16 16
   Streptomycin 1–256 64b
Tetracycline 1–16 16

aNCCLS, National Committee for Clinical Laboratory Standards. Antimicrobial susceptibility testing was performed according to NCCLS standards (20). Escherichia coli (ATCC 25922 and ATCC 35218), Enterococcus faecalis (ATCC 51299), and Pseudomonas aeurigonosa (ATCC 27853) were used as quality controls.
bNCCLS breakpoint not established for E. coli.

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