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

Flauta, Victor; Osterhout, Gerard; Ellis, Brandon; Grayson, Michael; Sasser, Myron; Cohen, Sam; Sander, Melissa; Dionne, Kim; Carroll, Karen; Parrish, Nicole

doi:10.1016/j.diagmicrobio.2009.12.008

« Previous Next »Diagnostic Microbiology & Infectious Disease
Volume 67, Issue 1 , Pages 47-51, May 2010

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

Victor Flauta
- Division of Medical Microbiology, Department of Pathology, Johns Hopkins University, Baltimore, MD 21287, USA
Gerard Osterhout
- MIDI, Incorporated, 125 Sandy Drive, Newark, DE 19713, USA
Brandon Ellis
- Division of Medical Microbiology, Department of Pathology, Johns Hopkins University, Baltimore, MD 21287, USA
Michael Grayson
- Division of Medical Microbiology, Department of Pathology, Johns Hopkins University, Baltimore, MD 21287, USA
Myron Sasser
- MIDI, Incorporated, 125 Sandy Drive, Newark, DE 19713, USA
Sam Cohen
- ARUP Laboratories, 500 Chipeta Way, Salt Lake City, UT 84108, USA
Melissa Sander
- Division of Medical Microbiology, Department of Pathology, Johns Hopkins University, Baltimore, MD 21287, USA
Kim Dionne
- Division of Medical Microbiology, Department of Pathology, Johns Hopkins University, Baltimore, MD 21287, USA
Karen Carroll
- Division of Medical Microbiology, Department of Pathology, Johns Hopkins University, Baltimore, MD 21287, USA
Nicole Parrish
- Division of Medical Microbiology, Department of Pathology, Johns Hopkins University, Baltimore, MD 21287, USA
- Corresponding author. Johns Hopkins University, Baltimore, MD 21287, USA. Tel.: +1-410-955-5077; fax: +1-410-614-8087.

Received 3 August 2009; accepted 11 December 2009. published online 15 March 2010.

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 μg/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 μg/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.

Keywords: Mycobacterium avium complex, Susceptibility testing, RAM