Skip to main navigation menu Skip to main content Skip to site footer

Original article

Vol. 140 No. 3738 (2010)

Comparison of MALDI TOF with conventional identification of clinically relevant bacteria

  • M Risch
  • D Radjenovic
  • JN Han
  • M Wydler
  • U Nydegger
Cite this as:
Swiss Med Wkly. 2010;140:w13095


BACKGROUND: A completely new approach to diagnose microbial agents at least one day earlier based on mass spectrometric analysis becomes possible in the microbiology laboratory: MALDI TOF: matrix-assisted laser desorption/ionisation time-of-flight. Comparison between results of the new procedure with those obtained by conventional testing is mandatory.

METHODS: 204 clinical isolates grown on agar plates were analysed both, by the MALDI TOF Bruker microflex apparatus and by conventional identification using the VITEK II and API systems, both from bioMérieux.

RESULTS: Of the identified isolates, 72 were gram-positive and 130 gram-negative; 2 were yeasts (candida). Concordance was seen with 61/72 (85%) of the Gram-positive bacteria and with 115/130 (88%) of the Gram-negative bacteria. In 27 samples (13.2%), a discrepancy of the species and/or genus was obvious. The discrepancy appeared with 16 gram-negative (12.2%) and with 11 gram-positive germs (15.3%, n.s.). In the latter group, 6 samples showed discordance with Streptococcus pneumoniae (MALDI) and Streptococcus mitis/oralis (conventional identification) constellation. Among gram-negative samples, most differences occurred on the species level only, e.g. Enterobacter cloacae versus Enterobacter kobei. In 5 cases, discordance was major and appeared on the genus level: Enterobacter/Raoultella, Streptococcus/Gemella, Pseumdomonas/Burkholderia, Microbacter/Sphingomonas and Candida/Cryptococcus. The most outstanding difference was Microbacterium arborescens (MALDI TOF) and Sphingomonas paucimobilis (conventional). Molecular biological identification of two Streptococcus mitisgroup bacteria confirmed the erroneous diagnosis by MALDI TOF of Streptococcus pneumoniae.

CONCLUSION: Good comparability between MALDI TOF analysis and conventional identification procedures (86.8%) but special caution is needed when identifying streptococcal species.


  1. Seng P, Drancourt M, Gouriet F, La Scola B, Forunier PE, Rolain JM, et al. Ongoing revolution in bacteriology: routine identification of bacteria by matrix-assisted laser desorption ionization time-of-flight mass spectrometry. Clin Infect Dis. 2009;49:543–51.
  2. Cherkaoui A, Hibbs, J, Emonet S, Tangomo M, Girard M, Francois P, Schrenzel J. Comparison of two matrix-assisted laser desorption ionization-time of flight mass spectrometry methods with conventional phenotypic identification for routine identification of bacteria to the species level. J Clin Microbiol. 2010;48(4):1169–75.
  3. Bizzini A, Durussel C, Bille J, Greub G, Prod’hom G. Performance of matrix-assisted laser desorption ionization-time of flight mass spectrometry for identification of bacterial strains routinely isolated in a clinical microbiology laboratory. J Clin Microbiol. 2010;48(5):1549–54.
  4. Stevenson LG, Drake SK, Murray PR. Rapid identification of bacteria in positive blood culture broths by MALDI TOF mass spectrometry. J Clin Microbiol. 2010;48(2):444–7.
  5. Mellmann A, Cloud J, Maier T, Keckovoet U, Ramminger I, Iwen P, et al. 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. J Clin Microbiol. 2008;46(6):1946–54.
  6. Kilian M, Polsen K, Blomqvist T, Havarstein LS, Bek-Thomsen M, Tettelin H, et al. Evolution of streptococcus pneumoniae and its close commensal relatives PloS On e 2008;3(7):e2683.
  7. Marr N, Luu RA, Fernandez RC. Bordetella pertussis binds human C1 esterase inhibitor during the virulent phase, to evade complement-mediated killing. J Infect Dis. 2007;195(4):585–8.
  8. Hair PS, Echague CG, Sholl AM, Watkins JA, Geoghegan JA, Foster TJ, et al. Clumping factor A interaction with complement factor I increases C3b cleavage on the bacterial surface of staphylococcus aureus, and decreases complement-mediated phagocytosis. Infect Immun. 2010;78(4):1717–27.
  9. Spanu T, De Carolis E, Fiori B, Sanguinetti M, D’Inzeo T, Fadda G, et al. Evaluation of matrix-assisted laser desorption ionization-time-of-flight mass spectrometry in comparison to rpoB gene sequencing for species identification of bloodstream infection staphylococcal isolates. Clin Microbiol Infect 2010; Feb 2 (Epub ahead of print).
  10. Tissari P, Zumla A, Tarkka E, Mero S, Savolainen L, Vaara M, et al. Accurate and rapid identification of bacterial species from positive blood cultures with a DNA-based microarray platform: an observational study. Lancet. 2010;375(9710):224–30.