Table 2.

Antimicrobial resistance of E. coliO157:H7 and non-O157 STEC isolates

Class and/or antimicrobial% Resistant isolatesa
O157:H7Other STEC
β-Lactams
 Ampicillin1433
 Amoxicillin-clavulanic acid05
Cephalosporins
 Cephalothin019
 Ceftiofur00
 Ceftriaxone00
Phenicols
 Chloramphenicol029
 Florfenicolb 010
Tetracycline9343
Aminoglycosides
 Amikacin00
 Apramycin00
 Kanamycin2119
 Gentamicin00
 Streptomycin7643
Sulfonamides and/or trimethoprim
 Sulfamethoxazole9348
 Trimethoprim-sulfamethoxazole019
Quinolones (including fluoroquinolones)
 Nalidixic acid00
 Ciprofloxacin00
  • a MICs were determined via microdilution methods according to NCCLS guidelines (20, 21). E. coli O157, 29 isolates; non-O157 STEC, 21 isolates.

  • b The resistant breakpoint used was ≥16 μg/ml.