T Maier

Publications of T Maier

• Short communication: Identification of subclinical cow mastitis pathogens in milk by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

  Authors: J R Barreiro, C R Ferreira, G B Sanvido, M Kostrzewa, T Maier, B Wegemann, V Böttcher, M N Eberlin, M V dos Santos

  Journal of dairy science. 12/2010; 93(12):5661-7.

  Subclinical mastitis is a common and easily disseminated disease in dairy herds. Its routine diagnosis via bacterial culture and biochemical identification is a difficult and time-consuming process.Subclinical mastitis is a common and easily disseminated disease in dairy herds. Its routine diagnosis via bacterial culture and biochemical identification is a difficult and time-consuming process. In this work, we show that matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) allows bacterial identification with high confidence and speed (1 d for bacterial growth and analysis). With the use of MALDI-TOF MS, 33 bacterial culture isolates from milk of different dairy cows from several farms were analyzed, and the results were compared with those obtained by classical biochemical methods. This proof-of-concept case demonstrates the reliability of MALDI-TOF MS bacterial identification, and its increased selectivity as illustrated by the additional identification of coagulase-negative Staphylococcus species and mixed bacterial cultures. Matrix-assisted laser desorption-ionization mass spectrometry considerably accelerates the diagnosis of mastitis pathogens, especially in cases of subclinical mastitis. More immediate and efficient animal management strategies for mastitis and milk quality control in the dairy industry can therefore be applied.

• Identification of Francisella tularensis by whole-cell matrix-assisted laser desorption ionization-time of flight mass spectrometry: fast, reliable, robust, and cost-effective differentiation on species and subspecies levels.

  Authors: E Seibold, T Maier, M Kostrzewa, E Zeman, W Splettstoesser

  Journal of clinical microbiology. 02/2010; 48(4):1061-9.

  Francisella tularensis, the causative agent of tularemia, is a potential agent of bioterrorism. The phenotypic discrimination of closely related, but differently virulent, Francisella tularensisFrancisella tularensis, the causative agent of tularemia, is a potential agent of bioterrorism. The phenotypic discrimination of closely related, but differently virulent, Francisella tularensis subspecies with phenotyping methods is difficult and time-consuming, often producing ambiguous results. As a fast and simple alternative, matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) was applied to 50 different strains of the genus Francisella to assess its ability to identify and discriminate between strains according to their designated species and subspecies. Reference spectra from five representative strains of Francisella philomiragia, Francisella tularensis subsp. tularensis, Francisella tularensis subsp. holarctica, Francisella tularensis subsp. mediasiatica, and Francisella tularensis subsp. novicida were established and evaluated for their capability to correctly identify Francisella species and subspecies by matching a collection of spectra from 45 blind-coded Francisella strains against a database containing the five reference spectra and 3,287 spectra from other microorganisms. As a reference method for identification of strains from the genus Francisella, 23S rRNA gene sequencing was used. All strains were correctly identified, with both methods showing perfect agreement at the species level as well as at the subspecies level. The identification of Francisella strains by MALDI-TOF MS and subsequent database matching was reproducible using biological replicates, different culture media, different cultivation times, different serial in vitro passages of the same strain, different preparation protocols, and different mass spectrometers.

• High Inter-Laboratory Reproducibility of MALDI-TOF Mass Spectrometry-Based Species Identification of Nonfermenting Bacteria.

  Authors: A Mellmann, F Bimet, C Bizet, A. D. Borovskaya, R. R. Drake, U Eigner, A M Fahr, Y. He, E. N. Ilina, M Kostrzewa, T Maier, L Mancinelli, W. Moussaoui, G Prévost, L Putignani, C. L. Seachord, Y. W. Tang, D Harmsen

  Journal of clinical microbiology. 09/2009;

  MALDI-TOF MS has emerged as rapid, cost-effective alternative for bacterial species identification. Identifying 60 blind-coded nonfermenting bacteria samples, this international study (eightMALDI-TOF MS has emerged as rapid, cost-effective alternative for bacterial species identification. Identifying 60 blind-coded nonfermenting bacteria samples, this international study (eight laboratories) achieved 98.75% inter-laboratory reproducibility. Only six of 480 samples were misidentified due to interchanges (4 samples) or contamination (1), or not identified because of insufficient signal intensity (1).

• MALDI - TOF Mass-Spectrometry for Fast and Reliable Identification of Clinical Yeast Isolates.

  Authors: G Marklein, M Josten, U. Klanke, E. Müller, R Horré, T Maier, T Wenzel, M Kostrzewa, G Bierbaum, A. Hoerauf, H G Sahl

  Journal of clinical microbiology. 08/2009;

  The clinical impact of severe infections with yeasts and yeast-like fungi has increased especially in immunocompromised hosts. In recent years new antifungal agents have become available withThe clinical impact of severe infections with yeasts and yeast-like fungi has increased especially in immunocompromised hosts. In recent years new antifungal agents have become available with different and partially species-specific activity patterns. Therefore, rapid and reliable species identification is essential for antifungal treatment, however, conventional biochemical methods are time consuming and require considerable expertise. We evaluated matrix-assisted laser desorption ionisation-time-of-flight mass spectrometry (MALDI-TOF MS) for the rapid routine identification of clinical yeast isolates. A total of 18 type collection strains and 267 recent clinical isolates of Candida (n=250), Cryptococcus, Saccharomyces, Trichosporon, Geotrichum, Pichia, and Blastoschizomyces spp. were identified employing MALDI-TOF MS. Results were compared with those of conventional phenotyping and biochemical tests including ID-32C (API bioMérieux, Nürtingen, Germany). Starting with cells from single colonies, accurate species identification by MALDI-TOF MS was achieved for 247 of the clinical isolates (92.5%). The remaining 20 isolates required complementation of the reference database with appropriate reference strains which were obtained from type culture collections or identified by 26S rDNA sequencing. The absence of a suitable reference strain from the MALDI-TOF MS database was clearly indicated by too low log score values for the respective clinical isolates, i.e. no false positive identification occurred. After complementation of the database, all isolates were unambiguously identified. The established API-ID-32C biochemical diagnostic system identified 244 isolates in a first round. Overall, MALDI-TOF MS proved a most rapid and reliable identification tool for yeasts and yeast-like fungi combining lowest expenditure of consumables and easy interpretion, and fast turnaround time.

• Species identification of clinical isolates of Bacteroides by matrix-assisted laser-desorption/ionization time-of-flight mass spectrometry.

  Authors: E Nagy, T Maier, E Urban, G Terhes, M Kostrzewa

  Clinical microbiology and infection : the official publication of the European Society of Clinical Microbiology and Infectious Diseases. 05/2009;

  Clin Microbiol InfectAbstract Bacteroides fragilis and related species are important human pathogens involved in mixed infections of different origins. The B. fragilis group isolates areClin Microbiol InfectAbstract Bacteroides fragilis and related species are important human pathogens involved in mixed infections of different origins. The B. fragilis group isolates are phenotypically very similar, grow more slowly than aerobic bacteria and, accordingly, are frequently misidentifed with classical or automated phenotypical identification methods. Recent taxonomic changes and new species accepted as members of the Bacteroides genus are not included in the different databases of commercially available identification kits. The use of matrix-assisted laser-desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was therefore evaluated for the species identification of 277 clinical isolates of the Bacteroides genus. Species identification was carried out with MALDI Bruker Daltonik Biotyper software (Bruker Daltonik GmbH, Bremen, Germany) by comparing the mass spectrum of each strain with the mass spectra of the 3260 reference strains currently available. The results of conventional phenotypical identification of the isolates were used as a reference. 16S rRNA gene sequencing was performed for a selection of the strains that gave discrepant results and for all those inconclusively identified by MALDI-TOF MS; 270 isolates (97.5%) were unequivocally identified [log(score) >/=2.0] by comparison with the reference strains present in the MALDI Biotyper database. Of the 23 isolates for which the MALDI-TOF MS species identification differed from the conventional phenotypical identification, 11 were sequenced. The sequencing data confirmed the MALDI-TOF MS result in ten cases and, for the remaining isolate, the sequencing data did not lead to the determination of the species, but only to that of the genus (Bacteroides sp.). The discriminating power and identification accuracy of MALDI-TOF MS proved to be superior to that of biochemical testing for Bacteroides thetaiotaomicron, Bacteroides ovatus and Bacteroides uniformis.

• Evaluation of matrix-assisted laser desorption ionization-time-of-flight mass spectrometry in comparison to 16S rRNA gene sequencing for species identification of nonfermenting bacteria.

  Authors: A Mellmann, J Cloud, T Maier, U Keckevoet, I Ramminger, P Iwen, J Dunn, G Hall, D Wilson, P Lasala, M Kostrzewa, D Harmsen

  Journal of clinical microbiology. 06/2008; 46(6):1946-54.

  Nonfermenting bacteria are ubiquitous environmental opportunists that cause infections in humans, especially compromised patients. Due to their limited biochemical reactivity and differentNonfermenting bacteria are ubiquitous environmental opportunists that cause infections in humans, especially compromised patients. Due to their limited biochemical reactivity and different morphotypes, misidentification by classical phenotypic means occurs frequently. Therefore, we evaluated the use of matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS) for species identification. By using 248 nonfermenting culture collection strains composed of 37 genera most relevant to human infections, a reference database was established for MALDI-TOF MS-based species identification according to the manufacturer's recommendations for microflex measurement and MALDI BioTyper software (Bruker Daltonik GmbH, Leipzig, Germany), i.e., by using a mass range of 2,000 to 20,000 Da and a new pattern-matching algorithm. To evaluate the database, 80 blind-coded clinical nonfermenting bacterial strains were analyzed. As a reference method for species designation, partial 16S rRNA gene sequencing was applied. By 16S rRNA gene sequencing, 57 of the 80 isolates produced a unique species identification (>or=99% sequence similarity); 11 further isolates gave ambiguous results at this threshold and were rated as identified to the genus level only. Ten isolates were identified to the genus level (>or=97% similarity); and two isolates had similarity values below this threshold, were counted as not identified, and were excluded from further analysis. MALDI-TOF MS identified 67 of the 78 isolates (85.9%) included, in agreement with the results of the reference method; 9 were misidentified and 2 were unidentified. The identities of 10 randomly selected strains were 100% correct when three different mass spectrometers and four different cultivation media were used. Thus, MALDI-TOF MS-based species identification of nonfermenting bacteria provided accurate and reproducible results within 10 min without any substantial costs for consumables.