Matrix-Assisted Laser Desorption/Ionization Time-Of-Flight Mass Spectrometry (MALDI-TOF MS) has been introduced as a rapid, high-throughput and low-cost tool for genus/species-level identification in medical, environmental and food-related studies of pure cultures. MALDI-TOF MS is a soft ionization technique allowing desorption and ionization of biomolecules, such as proteins and peptides (mainly of ribosomal origin), in a non-destructive manner and couples high sensitivity with accuracy. The generated ions provide a peptide fingerprint, i.e. mass spectrum, that can be used to characterize and identify bacteria at genus/species-level, provided that the species is represented in the identification database. This is achieved by comparing the mass spectra generated of unknown bacterial strains to a reference database containing mass spectra generated from well-characterized bacterial strains.
At BCCM/LMG, identification of bacterial cultures is offered as a high-throughput and fast customer service using the MALDI-TOF MS system MicroflexTM LT of Bruker Daltonics (Bremen, Germany). This commercial system includes an extensive database comprising numerous mass spectra generated mostly from clinically relevant bacteria. BCCM/LMG harbors a collection of numerous well-characterized bacterial strains isolated from a diverse set of niches (e.g., food, clinical, veterinary, agricultural, aquatic and other environmental niches). Strains from this collection are carefully selected based on our in-house expertise, to build a proprietary MALDI-TOF MS identification database with sufficient coverage of the intraspecies diversity, to meet the needs of the client community. For pure cultures, belonging to a species that is not yet included in the MALDI-TOF MS identification database, classical identification techniques (e.g., DNA sequencing analysis) are performed as an alternative.
The service report provided to our customers includes a detailed description of the technique used, the confidence score obtained with the most related species present in the mass spectral identification database and a scientific conclusion on the identity of the isolate(s) provided by the client.