Evaluation of the etest for detection of tetracycline resistance in mycoplasma hominis

Academic Article


  • The Etest was compared with microbroth dilution for performing in vitro susceptibility tests in 38 isolates of Mycoplasma hominis chosen to represent a wide range of MIC values. MIC50s were 4 μg/ml for both methods; whereas, MIC90s were 64 and >256 μg/ml for broth and Etest, respectively. Etest MICs determined on SP 4 agar were usually two or more dilutions greater than microbroth MICs in SP 4 broth, and values were prone to change by one to two dilutions when different inoculum densities were used. Inocula of 105 to 106 color-changing units/ml gave the most consistently readable MICs, with discrete colony formation surrounding the ellipse. Etest MICs for 5 isolates tested a second time at the same inoculum on SP 4 agar agreed with the original value within 1 dilution. For 12 isolates tested on A 8 agar simultaneously with SP 4 agar, MICs for 10/12 agreed within one dilution; whereas, in the other 2 isolates, MICs varied by two dilutions. These findings suggest that the Etest, when properly controlled, can be used to determine tetracycline MICs for M. hominis.
  • Authors

    Digital Object Identifier (doi)

    Author List

  • Waites KB; Crabb DM; Duffy LB; Cassell GH
  • Start Page

  • 117
  • End Page

  • 122
  • Volume

  • 27
  • Issue

  • 4