Identification of pathogens by mass spectrometry

Abstract

Background: Mass spectrometry (MS) is a suitable technology for microorganism identification and characterization.

Content: This review summarizes the MS-based methods currently used for the analyses of pathogens. Direct analysis of whole pathogenic microbial cells using MS without sample fractionation reveals specific biomarkers for taxonomy and provides rapid and high-throughput capabilities. MS coupled with various chromatography- and affinity-based techniques simplifies the complexity of the signals of the microbial biomarkers and provides more accurate results. Affinity-based methods, including those employing nanotechnology, can be used to concentrate traces of target microorganisms from sample solutions and, thereby, improve detection limits. Approaches combining amplification of nucleic acid targets from pathogens with MS-based detection are alternatives to biomarker analyses. Many data analysis methods, including multivariate analysis and bioinformatics approaches, have been developed for microbial identification. The review concludes with some current clinical applications of MS in the identification and typing of infectious microorganisms, as well as some perspectives.

Summary: Advances in instrumentation (separation and mass analysis), ionization techniques, and biological methodologies will all enhance the capabilities of MS for the analysis of pathogens.

Figure 1.

Flow chart of microbial enrichment and analysis strategies for the identification of microorganisms.

Figure 2.

Representation of the process for using POA-bound Fe₃O₄@Al₂O₃ magnetic nanoparticles to trap target bacteria. The particles were vortex-mixed with a bacterial sample for 1 h before isolation. The isolated conjugates were mixed with sinapinic acid and subjected to MALDI analysis. S.S., S. saprophyticus. Reprinted, with permission, from Liu et al. (3), © 2009 (American Chemical Society).

Figure 3.

MALDI spectra obtained from direct analysis of intact bacterial cells of S. aureus, E. faecalis, E. coli, and V. parahaemolyticus. Spectra were acquired in the linear mode using a time-of-flight mass spectrometer. Each sample contained 10⁷ CFU bacteria. a.u., arbitrary units.

Figure 4.

Deconvoluted ESI mass spectra of both strands of the tkt gene amplicons from 6 C. jejuni strains. Both the forward (◊) and the reverse (#) strands of the PCR amplicons from each strain are clearly observed. The base compositions are listed to the left of the spectra. Reprinted, with permission, from Hannis et al. (49), © 2009 (American Society for Microbiology).