Comparison of Etest, Vitek and Agar Dilution for Susceptibility Testing of Colistin

Clin Microbiol Infect. 2007 May;13(5):541-4. doi: 10.1111/j.1469-0691.2007.01708.x. Epub 2007 Mar 19.

Abstract

In total, 172 isolates of Enterobacteriaceae, Acinetobacter spp., Pseudomonas aeruginosa and Stenotrophomonas maltophilia were tested for susceptibility to colistin by agar dilution, Etest and the Vitek 2 system. Isolates with a colistin MIC < or =2 mg/L were considered to be susceptible. Fifty-four (31%) Gram-negative isolates were resistant to colistin. Categorical agreement between agar dilution and Etest was 87%, and between agar dilution and Vitek 2 was 82%. Based on the data obtained, the Vitek 2 system was unreliable for detecting colistin resistance, and results obtained by Etest may require confirmation by a standard MIC susceptibility testing method.

Publication types

  • Comparative Study
  • Evaluation Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anti-Bacterial Agents / pharmacology*
  • Colistin / pharmacology*
  • Colony Count, Microbial
  • Enterobacteriaceae / drug effects
  • Gram-Negative Aerobic Rods and Cocci / drug effects
  • Humans
  • Microbial Sensitivity Tests / instrumentation*
  • Microbial Sensitivity Tests / methods*

Substances

  • Anti-Bacterial Agents
  • Colistin