MALDI‐TOF MS for Microbial Identification: Years of Experimental Development to an Established Protocol

Immediately after the first MALDI-TOF instrument became available, microbiologists have been investigating its potential as a platform for high throughput identification of microorganisms. A remarkable finding very early in these investigations was that despite the dynamic nature of the bacterial cell, components of the mass spectral profile were sufficiently stable and remained unchanged in spite of changes in environmental parameters. Further, mass spectral pattern have been found to be taxon specific and thus, consequently, numerous methods were reported that purported to provide an alternative to current identification systems. The SARAMIS system described herein sequentially extracts core stable mass ions from analyses of multiple individual strains of a particular species to yield a 'SuperSpectrum', a list of biomarkers that are weighted according to their specificity from family to (sub)species levels. This approach has been used successfully to identify microorganisms from diverse phylogenetic lines of bacteria and fungi with considerable success. The protocol described has evolved of over years of experimental work to yield a robust system that can readily be applied for routine microbiological identification in a clinical diagnostic laboratory.