MALDI-TOF MS technology, which is based on the analysis of the entire bacterial proteome in the mass range of 2-20 kDa, is a rapid, cheap, high-throughput and simple method that has been successfully used by diagnostic laboratories for species and strain identification of different microorganisms, especially pathogenic bacteria.
Additionally, it can be used to identify meat species (such as mammalian animals, fish, and insects). Therefore, the technology can also contribute to the detection of food fraud, such as false claims regarding the animal species used in a food product. In recent years, MALDI-TOF MS-based methods are receiving attention as an approach for rapid detection of antimicrobial resistance to several antibiotics, such as β-Lactams, carbapenems and polymyxins. Depending on the mechanism of resistance, MALDI-TOF MS spectra can be used for antimicrobial susceptibility testing (AST) to: (i) detect metabolites related to degradation of antibiotics, (ii) detect a peak shift related to a mutation in the biomarker gene, (iii) detect unique biomarkers related to the production of a specific molecule (β-Lactamase, rRNA methyl-transferase activity). While AST by MALDI-TOF MS would still require an additional step of co-incubation of bacterial cultures with antibiotics (about 3-5 hours), this nonetheless shortens significantly the time compared to AST by broth microdilution or disc diffusion.
Dr. Samart Dorn-In
Identification of species/genus of microorganisms
Methods & Expertise for Research Infrastructure
To identify species or strain of microorganisms, pure cultures are required. They are usually subcultured on non-selective agar and incubated under optimal temperature and atmospheric conditions. The grown colonies can be extracted using direct or formic acid extraction methods (Bruker Daltonik GmbH). Extracted samples are spotted on a target plate. The MALDI-TOF MS measurements are performed using a Microflex LT. The analysis of the generated data is executed with the provided software and its automated settings.
For the identification of animal species and the antimicrobial susceptibility testing (AST), the methods can be adopted from producer (Bruker Daltoniks GmbH), from publication, or it can be internally developed. The specific peaks of the protein spectra regarding species identification, mutation or metabolites related to degradation of antibiotics will be analyzed and identified. For this step, the reference spectra of microbial/animal species or antimicrobial metabolite products are required, either acquired from producer Bruker Daltoniks GmbH or internally developed.
Dr. Samart Dorn-In (Samart.Dorn-In@vetmeduni.ac.at)