MALDI-TOF

Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) may be used to analyze the protein composition of cells. The composition of these proteins in the bacterial cells is unique to each species; at the present time, several commercial systems have databases that include the identification of Nocardia, but full FDA approval at this time is limited in scope.^37(6.4.3) MALDI-TOF is useful in research, university, and CDC laboratories for the identification of organisms at the species level. Many of the larger medical microbiology laboratories now possess MALDI-TOF instrumentation for use in the analysis of routine bacterial isolates.

MALDI-TOF is fast and relatively simple once the laboratory obtains the required complex instrumentation. An expanded database for identifying the aerobic actinomycetes (Nocardia and others) is required. In the near future, MALDI-TOF identification may be one of the most promising methods for use by both large and small routine clinical microbiology laboratories.

One major limitation remains the finite database for referencing the organism identifications. Aerobic actinomycetes remain relatively infrequently isolated human pathogens when compared to other bacterial isolates. Many times, "no identification" may result when the specimen is tested using MALDI-TOF. As more and more of these organisms are tested and entered into commercial and research databases, this method will prove most useful.