Variations in bacitracin susceptibility observed in Staphylococcus and Micrococcus species

J Clin Microbiol. 1986 May;23(5):963-4. doi: 10.1128/jcm.23.5.963-964.1986.


Bacitracin susceptibility was evaluated as a laboratory method to differentiate staphylococci from micrococci. A total of 317 staphylococcal isolates and 108 micrococcal isolates were each tested for susceptibility to bacitracin by a disk-diffusion method using disks of three different potencies (0.04, 2.0, and 10.0 U) and a broth dilution method to obtain MICs. When a growth inhibition zone diameter breakpoint of greater than 10 mm was used to establish susceptibility with a 0.04-U disk, all micrococci were bacitracin susceptible and 94.6% of the staphylococci were resistant. Testing with disks of higher potency did not improve the specificity of the disk-diffusion method.

MeSH terms

  • Bacitracin / pharmacology*
  • Dose-Response Relationship, Drug
  • Microbial Sensitivity Tests
  • Micrococcus / classification
  • Micrococcus / drug effects*
  • Staphylococcus / classification
  • Staphylococcus / drug effects*


  • Bacitracin