Ongoing revolution in bacteriology: routine identification of bacteria by matrix-assisted laser desorption ionization time-of-flight mass spectrometry.
BACKGROUND
Matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry accurately identifies both selected bacteria and bacteria in select clinical situations. It has not been evaluated for routine use in the clinic.


METHODS
We prospectively analyzed routine MALDI-TOF mass spectrometry identification in parallel with conventional phenotypic identification of bacteria regardless of phylum or source of isolation. Discrepancies were resolved by 16S ribosomal RNA and rpoB gene sequence-based molecular identification. Colonies (4 spots per isolate directly deposited on the MALDI-TOF plate) were analyzed using an Autoflex II Bruker Daltonik mass spectrometer. Peptidic spectra were compared with the Bruker BioTyper database, version 2.0, and the identification score was noted. Delays and costs of identification were measured.


RESULTS
Of 1660 bacterial isolates analyzed, 95.4% were correctly identified by MALDI-TOF mass spectrometry; 84.1% were identified at the species level, and 11.3% were identified at the genus level. In most cases, absence of identification (2.8% of isolates) and erroneous identification (1.7% of isolates) were due to improper database entries. Accurate MALDI-TOF mass spectrometry identification was significantly correlated with having 10 reference spectra in the database (P=.01). The mean time required for MALDI-TOF mass spectrometry identification of 1 isolate was 6 minutes for an estimated 22%-32% cost of current methods of identification.


CONCLUSIONS
MALDI-TOF mass spectrometry is a cost-effective, accurate method for routine identification of bacterial isolates in <1 h using a database comprising > or =10 reference spectra per bacterial species and a 1.9 identification score (Brucker system). It may replace Gram staining and biochemical identification in the near future.
Seng
Piseth
P
Pôle des Maladies Infectieuses, Assistance Publique-Hôpitaux de Marseille, URMITE, Unité Mixte de Recherche, Centre National de la Recherche Scientifique-Institut pour la Recherche et le Développement 6236, Université de la Méditerranée, Marseille, France.
Drancourt
Michel
M
Gouriet
Frédérique
F
La Scola
Bernard
B
Fournier
Pierre-Edouard
PE
Rolain
Jean Marc
JM
Raoult
Didier
D
D001419:Bacteria / Q000737:chemistry* / Q000145:classification* / Q000302:isolation & purification; D001424:Bacterial Infections / Q000175:diagnosis*; D001426:Bacterial Proteins / Q000032:analysis; D001431:Bacteriological Techniques / Q000191:economics / Q000379:methods*; D003951:Diagnostic Errors; D006801:Humans; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000191:economics / Q000379:methods*; D013997:Time Factors
D001426:Bacterial Proteins