i want to use MALDI -TOF biotyper to confirm the identity of a number of staph.aureus clinical isolates and i read a review that claimed its ability to provide a strain-level identification of bacteria , but when i contacted the responsible technician he seemed to have no idea about such thing , so i want to know if anyone has experienced this technology ?
another question , does MALDI-TOF differentiate between MRSA and MSSA ?
It is possible to do to some extent do serovar analysis, I'm sure it could be better. The main hurdle I encounter is the need to construct your serovar variants database on your instrument, as far as I know either the Bruker and the Biomerieux MALDI-TOF (the two main contenders here) could do that. As some collegue said before to construct this database the main hurdle is have some known reference standards of the most common serovar/strain outside the factory loaded ones. And work in Research Use Only mode, I don't think there exist some commercial MALDI-TOF MS that can identify strains out the factory database in Clinical/Industrial Use mode.
The answer is yes if we can prepare a sample that contains the strain-exclusive protein (effective protein enrichment and extraction are essential for that purpose, and the protein information is available on protein databank), for strain differentiation.
look at the link below
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4006720/pdf/pone.0087419.pdf
I have no hands on experience, but my colleagues tells me it is possible. We run the Bruker Biotyper, and I believe the general idea is to create your own database by running your known reference strains ~100 times per strain, and creating a database using the software. Afterwards, you can run your unknown samples and get good strain ID's.
I tried the MALDI-TOF Microflex Biotyper from Bruker on Brucella. Unlike, staphylococci, brucellae have a very high genetic and phenotypic homology, thus constitute a real challenge to the resolution of the technique. The technique managed to differentiate brucellae at least to the biovar level. MALDI-TOF MS is a very promising tool and a real revolution in the field of microbial biotyping. The main challenge scientists are currently working on is to use samples directly without the need of a pure culture and proteome extraction. Scientists are also struggling to include viruses as well.
It is possible to do to some extent do serovar analysis, I'm sure it could be better. The main hurdle I encounter is the need to construct your serovar variants database on your instrument, as far as I know either the Bruker and the Biomerieux MALDI-TOF (the two main contenders here) could do that. As some collegue said before to construct this database the main hurdle is have some known reference standards of the most common serovar/strain outside the factory loaded ones. And work in Research Use Only mode, I don't think there exist some commercial MALDI-TOF MS that can identify strains out the factory database in Clinical/Industrial Use mode.
Identify S. aureus with the Biotyper should be no problem. However, to differentiate different S. aureus strains on a routine level will be very difficult
It is possible to do, it is a matter of knowing the differences between the strains that you are testing and having the database to confirm how well these phenotypes/genotypes are conserved as Manilo Calvi said above. It is also possible to do this using genetic methods on a MALDI-TOF:
Mass spectrometry provides accurate characterization of two genetic marker types in Bacillus anthracis. BioTechniques 37:642-651.
We used these above methods with following markers to quickly identify specific strains:
Strain-Specific Single-Nucleotide Polymorphism Assays for the Bacillus anthracis Ames Strain. Journal of Clinical Micro. 2007
All the best!
Identification of S. aureus at the species level by MALDI-TOF MS should be no problem. Discrimination of S. aureus at the strain level is, however, challenging (see our paper below)
Article Insufficient discriminatory power of MALDI-TOF mass spectrom...
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