Comparison of disk diffusion testing with the broth microdilution reference method

SpeciesNo. of isolates with reference method MIC (μg/ml)a of:No. of isolates with MH agar disk diffusion resultb of:
≤ 2≥ 8ColistinPolymyxin B
E. coli95436
Klebsiella spp.177101041311
C. freundii49571112
P. aeruginosa641082
P. fluorescens212121
A. baumannii61c24 + 1c61c
Acinetobacter spp.111111
A. lwoffii111
S. maltophilia9954
E. cloacae13 + 6c512 + 2c33 + 4c
Enterobacter spp.131113104
  • a For easier comparison, the MICs obtained with the broth microdilution broth reference method have been divided in two categories.

  • b The number of isolates that were sensitive (S), intermediate (I), or resistant (R). Shown are the first measurements with either colistin or polymyxin B.

  • c Heteroresistant isolate.