Reliable identification at the species level of Brucella isolates with MALDI-TOF-MS
1 Department of Earth, Environmental, and Life Sciences, TNO, Lange Kleiweg 137, Rijswijk, P.O Box 45, The Netherlands
2 Department of Bacteriology, Diagnostic Laboratory for Infectious Diseases and Perinatal Screening, National Institute of Public Health and the Environment (RIVM), Antonie van Leeuwenhoeklaan 9, Bilthoven 3721, MA, The Netherlands
3 Histology and Molecular Biology Section, Army Medical and Veterinary Research Center, Via Santo Stefano Rotondo 4, 00184 Rome, Italy
4 Military Health Care Expertise Co-ordination Centre, Ministry of Defence, Noodweg 37, Hilversum 1213, PW, The Netherlands
BMC Microbiology 2011, 11:267 doi:10.1186/1471-2180-11-267Published: 23 December 2011
The genus Brucella contains highly infectious species that are classified as biological threat agents. The timely detection and identification of the microorganism involved is essential for an effective response not only to biological warfare attacks but also to natural outbreaks. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) is a rapid method for the analysis of biological samples. The advantages of this method, compared to conventional techniques, are rapidity, cost-effectiveness, accuracy and suitability for the high-throughput identification of bacteria. Discrepancies between taxonomy and genetic relatedness on the species and biovar level complicate the development of detection and identification assays.
In this study, the accurate identification of Brucella species using MALDI-TOF-MS was achieved by constructing a Brucella reference library based on multilocus variable-number tandem repeat analysis (MLVA) data. By comparing MS-spectra from Brucella species against a custom-made MALDI-TOF-MS reference library, MALDI-TOF-MS could be used as a rapid identification method for Brucella species. In this way, 99.3% of the 152 isolates tested were identified at the species level, and B. suis biovar 1 and 2 were identified at the level of their biovar. This result demonstrates that for Brucella, even minimal genomic differences between these serovars translate to specific proteomic differences.
MALDI-TOF-MS can be developed into a fast and reliable identification method for genetically highly related species when potential taxonomic and genetic inconsistencies are taken into consideration during the generation of the reference library.