Use of the "RAM" susceptibility testing method for rapid detection of clarithromycin resistance in the Mycobacterium avium complex.
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.
Division of Medical Microbiology, Department of Pathology, Johns Hopkins University, Baltimore, MD 21287, USA.
Victor
V
Flauta
Gerard
G
Osterhout
Brandon
B
Ellis
Michael
M
Grayson
Myron
M
Sasser
Sam
S
Cohen
Melissa
M
Sander
Kim
K
Dionne
Karen
K
Carroll
Nicole
N
Parrish
D000995:Antitubercular Agents / Q000494:pharmacology*; D017291:Clarithromycin / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods; D015269:Mycobacterium avium Complex / Q000187:drug effects*; D012680:Sensitivity and Specificity; D013997:Time Factors
D000995:Antitubercular Agents; D017291:Clarithromycin