Identification of microorganisms in the clinical laboratory is based traditionally on morphology and biochemical characteristics. For many species, identification may take days so a rapid species-specific method would improve patient care. Nucleic-acid based assays are sensitive and accurate methods for species identification but are relatively slow and labor intensive. MALDI-TOF mass spectrometry was evaluated for the rapid identification of microorganisms using Bruker Daltonics MALDI BioTyper software and either an in-house generated spectral library of 105 yeast reference strains or the manufacturer's library consisting mainly of bacteria.
In total, 86% of 115 yeast, 562 bacterial, and 210 blood isolates were correctly identified. Of the remainder, 12% were not identified, probably due to sample prep or low organism count, and 2% were identified as belonging to groups known by the manufacturer to be indistinguishable. Given these results, MALDI-TOF compares favorably to current techniques but MALDI-TOF is considerably faster and cheaper, thus making MALDI-TOF identification of microorganisms a preferred method for the routine identification of microorganisms. Considerations for using this method as a primary method for organism identification of clinical samples will be discussed.
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