Table 2.

Prevalence of flo and cmlA genes in chloramphenicol-resistant bovine E. coli

Chloramphenicol and/or florfenicol resistance genotypeMIC (μg/ml)aof:No. of isolates positive for resistance gene/ no. tested
flo ≤16–>25616–>25634/48
flo, cmlA 64–>25664–>2568/48
cmlA 32–>256≤8–644/48
  • a Determined by microdilution methods according to NCCLS standards and guidelines (24, 25).

  • b Resistance breakpoint, ≥32 μg/ml.

  • c Resistance breakpoint, ≥8 μg/ml.