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An Open List For Users

J. Rau1, T. Eisenberg2, R. Sting1
1Chemisches und Veterinäruntersuchungsamt Stuttgart
2Landesbetrieb Hessisches Landeslabor Gießen

The use of MALDI-TOF-Mass Spectrometry (MALDI-TOF MS) is spreading rapidly in many areas of application within food control, veterinary medical diagnostics, and clinical microbiology. An unknown microorganism can be identified by comparing its mass spectrum to that of a reference in a database. This database thus plays a central role in identification.

The systems (consisting of both hardware and software) employed by most users offer not only an extensive database supplied by the manufacturer, but also allow for the addition of one’s own data. These can be transferred within the device platform, making it possible to fill in diagnostic gaps more quickly. In our experience, this is especially valid for a series of special microorganisms from veterinary medical microbiology.

There are few databases available for other applications, such as the species identification of animal meat via MALDI-TOF MS, although a wide circle of users is interested in them.

In order to make information regarding high quality database entries available from users for users, we have set up an „open“ list, which can be downloaded from this web site. This list offers uniformly presented information regarding species names, isolate numbers and specimens, as well as details on the validity of the isolate designation (e.g. sequence data that corroborate the identification), and technical details of the entries (instrument, cultivation, preparation, etc.). The summary of data entries, and especially the contact information for the owner of the entries, shall be presented in this manner. No actual spectra will be available for free download on MALDI-UP. The copyrights to the data and the updating process of the equipment manufacturer will thereby not be affected.

A user guide to MALDI-UP is available here.

The list will be maintained on a subdomain and updated at fixed intervals within the framework of the website „UA-BW“. It is open to users under the aforementioned conditions for the purpose of mutual exchange of information. This concept was developed with assistance from employees at CVUA Stuttgart and the Hessen State Laboratory.

MALDI-VALI – A list of single spectra for the validation of MALDI-TOF MS databases

E. Hiller1, A. Männig1, Wind C2, Fuchs J3, Pölzelbauer C4, J. Rau1

1Chemisches und Veterinäruntersuchungsamt Stuttgart
2Chemisches und Veterinäruntersuchungsamt Freiburg
3Chemisches und Veterinäruntersuchungsamt Karlsruhe
4Chemisches und Veterinäruntersuchungsamt Sigmaringen

The device and software used by many MALDI-TOF MS users contain comprehensive database entries for microbiology. For these databases, the manufacturer offer step-by-step updates, including improvement of individual entries, adjustments to taxonomic changes, or expansion to other groups of microorganisms. In addition, users can also create their own database entries or supplement entries generated by other users.

Each supplemented or modified database entry – either by a manufacturer update or by users’ own activities – directly affects the results of identification, e.g., one "unidentified" sample based on the old database could become "uniquely assigned to a species" according to the new database. Therefore, the examination of the overall system of device and flexible database requires a special validation strategy.

For fast validation of modified database compilations, a continuous collection of single spectra of reliable identified and well-documented microbial isolates or other sample materials can be applied [cf. Rau et al., 2016]. The official food control authorities in Baden-Wuerttemberg pursue a multi-site validation and collect the information on isolates as well as the obtained MS spectra. Other users have already released free available MS spectra collections that can be easily integrated here [e.g. Lasch et al., 2016].

Since 17.02.2017 information on single spectra of validly named isolates and materials can be found on the tab "Validation-Spectra" in the MALDI-UP list. As with database entries, mutual exchanges and shared benefits are in foreground of the "MALDI-VALI", and as an integral part of the MALDI-UP list, it is open to users under the same conditions for publishing information.

Rau J, Männig A, Hiller E, Mauder N, Wind C, Horlacher S, Kadlec K, Schwarz S, Contzen M (2016); MALDI-TOF mass spectrometry for reliable identification of bacteria – A validation based on Staphylococcaceae field isolates; Aspects of food control and animal health; 2016/03.

Lasch P, Stämmler M, Schneider A (2018); Version 3 (20181130) of the MALDI-TOF Mass Spectrometry Database for Identification and Classification of Highly Pathogenic Microorganisms from the Robert Koch-Institute (RKI) [Data set]; Zenodo.