Use of the "RAM" susceptibility testing method for rapid detection of clarithromycin resistance in the Mycobacterium avium complex

Diagn Microbiol Infect Dis. 2010 May;67(1):47-51. doi: 10.1016/j.diagmicrobio.2009.12.008. Epub 2010 Mar 12.

Abstract

Standard susceptibility testing of the Mycobacterium avium complex (MAC) can require 7 to 14 days from initial isolation. We evaluated a high-performance liquid chromatography-based susceptibility test for rapid determination of clarithromycin (CLR) resistance in MAC. This method can be completed in 72 h of incubation. A total of 110 MAC strains were tested using the following concentrations of CLR: 4, 16, and 64 microg/mL, for a total of 330 tests. Microbroth dilution was used as the reference method. Rapid analysis of mycolic acid ("RAM") concordance with the reference method for CLR susceptibility was 98% (254/258) and 100% for CLR resistance (72/72). The 4 discordant results occurred with 2 strains, which demonstrated intermediate resistance with an MIC of 16 microg/mL. This study demonstrates that "RAM"-based susceptibility testing for determination of CLR resistance in MAC is both rapid and accurate, providing a significant reduction in turn-around-time from 7 to 14 days to 72 h of incubation.

Publication types

  • Comparative Study
  • Evaluation Study

MeSH terms

  • Antitubercular Agents / pharmacology*
  • Clarithromycin / pharmacology*
  • Drug Resistance, Bacterial*
  • Humans
  • Microbial Sensitivity Tests / methods
  • Mycobacterium avium Complex / drug effects*
  • Sensitivity and Specificity
  • Time Factors

Substances

  • Antitubercular Agents
  • Clarithromycin