Stable-isotope-based strategies for rapid determination of drug resistance by mass spectrometry

Abstract

Mass spectrometry (MS) is one of several molecular-level technologies that have revolutionized the practice of clinical microbiology for accurate microorganism identification. Several different MS protocols and assays are being developed and implemented for screening and detection of drug-resistant strains of microorganisms. Functional assays that involve the combination of MS and stable-isotope labeling for establishing drug resistance are reviewed here. These assays include global or local labeling of growth media with C, N, or H stable isotopes in abundance ratios differing from the natural-isotope abundances of these elements. Drug resistance is determined by observing characteristic mass shifts of one or more microorganism-specific biomarkers. A related approach involves the amplification of organism-specific bacteriophages in targeted microorganisms. In this approach, the shift in biomarker masses for phages, initially proliferated in isotopically manipulated growth medium and subsequently grown in microorganisms in growth medium with elements of natural abundance ratios, is monitored and is an indication of drug resistance. Advantages of these assays as well as tools for automating the data analysis are also briefly discussed.