Matrix-assisted laser desorption ionization-time of flight mass spectrometry for the discrimination of food-borne microorganisms.
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ABSTRACT:
SUBMITTER: Mazzeo MF
PROVIDER: S-EPMC1392959 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:More than 20 different species of Mucorales can be responsible for human mucormycosis. Accurate identification to the species level is important. The morphological identification of Mucorales is not reliable, and the currently recommended identification standard is the molecular technique of sequencing the internal transcribed spacer regions. Nevertheless, matrix-assisted laser desorption ionization time-of-flight mass spectrometry has been shown to be an accurate alternative for the identification of bacteria, yeasts, and even filamentous fungi. Therefore, 38 Mucorales isolates, belonging to 12 different species or varieties, mainly from international collections, including 10 type or neo-type strains previously identified by molecular methods, were used to evaluate the usefulness of matrix-assisted laser desorption ionization time-of-flight mass spectrometry for the identification of human pathogenic Mucorales to the species level. One to three reference strains for each species were used to create a database of main spectrum profiles, and the remaining isolates were used as test isolates. A minimum of 10 spectra was used to build the main spectrum profile of each database strain. Interspecies discrimination for all the isolates, including species belonging to the same genus, was possible. Twenty isolates belonging to five species were used to test the database accuracy, and were correctly identified to the species level with a log-score >2. In summary, matrix-assisted laser desorption ionization time-of-flight mass spectrometry is a reliable and rapid method for the identification of most of the human pathogenic Mucorales to the species level.
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Project description:Antibiotic resistance in Gram-negative microorganisms is an increasing health care problem. The rapid detection of such resistance is crucial for starting an early specific therapy and to enable initiation of the required hygiene measures. With continued emphasis on reducing the cost of laboratory testing, only economical/low-cost approaches have a chance of being implemented. During recent years, matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) has been developed to be a standard method in microbiology laboratories for the rapid and cost-efficient identification of microorganisms. Extending the usage of MALDI-TOF MS in the clinical microbiology laboratory to the area of resistance testing is an attractive option. Quantitative MALDI-TOF MS using an internal standard facilitates the measurement of the quantity of peptides and small proteins within a spectrum. These quantities correlate to the number of microorganisms and therefore to the growth of a microorganism. The comparison of growth in the presence or absence of an antibiotic allows for analysis of the susceptibility behavior of a strain. Here, we describe a novel method and its application in the analysis of 108 Klebsiella sp. isolates. After 1 h of incubation at a meropenem concentration of 8 ?g/ml, a sensitivity of 97.3% and a specificity of 93.5% were achieved (compared to Etest results).
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Project description:Encapsulated Haemophilus influenzae strains belong to type-specific genetic lineages. Reliable capsule typing requires PCR, but a more efficient method would be useful. We evaluated capsule typing by using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. Isolates of all capsule types (a-f and nontypeable; n = 258) and isogenic capsule transformants (types a-d) were investigated. Principal component and biomarker analyses of mass spectra showed clustering, and mass peaks correlated with capsule type-specific genetic lineages. We used 31 selected isolates to construct a capsule typing database. Validation with the remaining isolates (n = 227) showed 100% sensitivity and 92.2% specificity for encapsulated strains (a-f; n = 61). Blinded validation of a supplemented database (n = 50) using clinical isolates (n = 126) showed 100% sensitivity and 100% specificity for encapsulated strains (b, e, and f; n = 28). MALDI-TOF mass spectrometry is an accurate method for capsule typing of H. influenzae.
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