Identification of bacteria isolated from veterinary clinical specimens using MALDI-TOF MS.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has recently emerged as a rapid and accurate identification method for bacterial species. Although it has been successfully applied for the identification of human pathogens, it has so far not been well evaluated for routine identification of veterinary bacterial isolates. This study was performed to compare and evaluate the performance of MALDI-TOF MS based identification of veterinary bacterial isolates with commercially available conventional test systems. Discrepancies of both methods were resolved by sequencing 16S rDNA and, if necessary, the infB gene for Actinobacillus isolates. A total of 375 consecutively isolated veterinary samples were collected. Among the 357 isolates (95.2%) correctly identified at the genus level by MALDI-TOF MS, 338 of them (90.1% of the total isolates) were also correctly identified at the species level. Conventional methods offered correct species identification for 319 isolates (85.1%). MALDI-TOF identification therefore offered more accurate identification of veterinary bacterial isolates. An update of the in-house mass spectra database with additional reference spectra clearly improved the identification results. In conclusion, the presented data suggest that MALDI-TOF MS is an appropriate platform for classification and identification of veterinary bacterial isolates.

MALDI-TOF MS based identification of food-borne yeast isolates.

In this study, food-borne yeast isolates (n=96), comprising at least 33 species, were identified using MALDI-TOF MS and conventional methods (API ID 32 C and Phoenix Yeast ID). Discrepancies of both methods were resolved by sequencing the ITS1-5.8S-rRNA-ITS2 region. For ten isolates, mainly classified to Rhodotorula and Trichosporon species, no clear final species identification was possible. 62 isolates were correctly identified to species level using either MALDI-TOF MS or conventional tests. 15 isolates were misidentified when applying conventional assays. In contrary, no species misidentifications were observed after MALDI-TOF MS based classification. In return, 16 isolates were not identifiable after matching their protein fingerprints against MALDI Biotyper 4.0.0.1 library. MALDI TOF MS in-house database update clearly improved the identification. In conclusion, the presented data suggest that MALDI-TOF MS is an appropriate platform for reliable classification and identification of food-borne yeast isolates.