Analysis of Microbial Mixtures by Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry

Wahl, Karen L.; Wunschel, Sharon C.; Jarman, Kristin H.; Valentine, Nancy B.; Petersen, Catherine E.; Kingsley, Mark T.; Zartolas, Kimberly A.; Saenz, Adam J.

doi:10.1021/ac0203847

Cited by 124 publications

(98 citation statements)

References 10 publications

(15 reference statements)

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“…The report of species-level identification for lower-scoring samples would increase test performance and appears to be safe unless groups with high spectral similarity between member species are involved (e.g., viridans streptococci). Modified identification algorithms, considering the presence of (nonbacterial) background peaks (45), might improve identification rates for crude samples without the specificity tradeoffs involved in lower score thresholds.…”

Section: Discussionmentioning

confidence: 99%

Rapid Identification of Bacteria from Positive Blood Culture Bottles by Use of Matrix-Assisted Laser Desorption-Ionization Time of Flight Mass Spectrometry Fingerprinting

Martin¹,

Rohde²,

Wolters³

et al. 2010

J Clin Microbiol

266

200

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Early and adequate antimicrobial therapy has been shown to improve the clinical outcome in bloodstream infections (BSI). To provide rapid pathogen identification for targeted treatment, we applied matrix-assisted laser desorption-ionization time of flight (MALDI-TOF) mass spectrometry fingerprinting to bacteria directly recovered from blood culture bottles. A total of 304 aerobic and anaerobic blood cultures, reported positive by a Bactec 9240 system, were subjected in parallel to differential centrifugation with subsequent mass spectrometry fingerprinting and reference identification using established microbiological methods. A representative spectrum of bloodstream pathogens was recovered from 277 samples that grew a single bacterial isolate. Species identification by direct mass spectrometry fingerprinting matched reference identification in 95% of these samples and worked equally well for aerobic and anaerobic culture bottles. Application of commonly used score cutoffs to classify the fingerprinting results led to an identification rate of 87%. Mismatching mostly resulted from insufficient bacterial numbers and preferentially occurred with Gram-positive samples. The respective spectra showed low concordance to database references and were effectively rejected by score thresholds. Spiking experiments and examination of the respective study samples even suggested applicability of the method to mixed cultures. With turnaround times around 100 min, the approach allowed for reliable pathogen identification at the day of blood culture positivity, providing treatment-relevant information within the critical phase of septic illness.

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Section: Discussionmentioning

confidence: 99%

Rapid Identification of Bacteria from Positive Blood Culture Bottles by Use of Matrix-Assisted Laser Desorption-Ionization Time of Flight Mass Spectrometry Fingerprinting

Martin¹,

Rohde²,

Wolters³

et al. 2010

J Clin Microbiol

266

200

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“…MALDI-TOF-MS has already been used to characterize bacteria (15,16,18,26,27). Among the various components identified in a spectra, only a few are specific for a given species; others are either strain specific or vary upon growth conditions (media, incubation time, etc.)…”

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confidence: 99%

Rapid Identification of Staphylococci Isolated in Clinical Microbiology Laboratories by Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry

et al. 2007

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Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF-MS) of intact bacteria yields a reproducible spectrum depending upon growth conditions, strain, or species. Using whole viable bacteria we describe here the application of MALDI-TOF-MS to the identification of coagulase-negative staphylococci (CoNS). Our aim was, once a bacterium has been recognized as Micrococcaceae, to identify peaks in the spectrum that can be used to identify the species or subspecies. MALDI-TOF-MS was performed using bacteria obtained from one isolated colony. One reference strain for each of the 23 clinically relevant species or subspecies of Micrococcaceae was selected. For each reference strain, the MALDI-TOF-MS profile of 10 colonies obtained from 10 different passages was analyzed. For each strain, only peaks that were conserved in the spectra of all 10 isolated colonies and with a relative intensity above 0.1 were retained, thus leading to a set of 3 to 14 selected peaks per strain. The MALDI-TOF-MS profile of 196 tested strains was then compared with that of the set of selected peaks of each of the 23 reference strains. In all cases the best hit was with the set of peaks of the reference strain belonging to the same species as that of the tested strain, thus demonstrating that the 23 sets of selected peaks can be used as a database for the rapid species identification of CoNS. Similar results were obtained using four different growth conditions. Extending this strategy to other groups of relevant pathogenic bacteria will allow rapid bacterial identification.

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“…The m/z values for mass spectral peaks and the patterns with which they are observed provide very specific and unbiased analysis, as they indicate molecular weights of true components of the sample. Bacterial cells have been identified by comparing MALDI-TOF spectra obtained from cultured bacterial cells and simple microbial mixtures against a library of known MALDI-TOF spectral fingerprints obtained from intact bacterial cells [3,4] or from comparison with masses predicted from a proteomic database [5,6]. The proteomic approach has been demonstrated to correctly identify bacteria from spectra originating at different laboratories [5], however, this approach is currently suffering from an incomplete protein database for many of the organisms that are of interest.…”

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confidence: 99%

Bacterial analysis by MALDI-TOF mass spectrometry: An inter-laboratory comparison

Wunschel

Jarman

Petersen

et al. 2005

J. Am. Soc. Mass Spectrom.

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118

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Bacterial analysis by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry has been demonstrated in numerous laboratories, and a few attempts have been made to compare results from different laboratories on the same organism. It has been difficult to understand the causes behind the observed differences between laboratories when different instruments, matrices, solvents, etc. are used. In order to establish this technique as a useful tool for bacterial identification, additional efforts in standardizing the methods by which MALDI mass spectra are obtained and comparisons of spectra from different instruments with different operators are needed. Presented here is an extension of our previous single-laboratory reproducibility study with three different laboratories in a controlled experiment with aliquots of the same bacterial culture, matrix stock solution, and calibrant standards. Using automated spectral collection of whole-cell bacteria and automated data processing and analysis algorithms, fingerprints from three different laboratories were constructed and compared. Nine of the ions appeared reproducibly within all three laboratories, with additional unique ions observed within each of the laboratories. An initial evaluation of the ability to use a fingerprint generated within one laboratory for bacterial identification of a sample from another laboratory is presented, and strategies for improving identification rates between laboratories is discussed. has been used to analyze intact, cultured microorganisms with minimal sample handling. Two recent review articles, which include the capabilities and current limitations that need to be addressed, provide an excellent overview of this emerging research field [1,2]. The MALDI-TOF MS technique for identifying biomolecules provides rapid analysis time (Ͻ1 min per sample analysis), low sample-volume requirements (Ͻ1 L fluid), and the highly selective nature of mass-spectrometric analysis based on relative molecular masses. The m/z values for mass spectral peaks and the patterns with which they are observed provide very specific and unbiased analysis, as they indicate molecular weights of true components of the sample. Bacterial cells have been identified by comparing MALDI-TOF spectra obtained from cultured bacterial cells and simple microbial mixtures against a library of known MALDI-TOF spectral fingerprints obtained from intact bacterial cells [3,4] or from comparison with masses predicted from a proteomic database [5,6]. The proteomic approach has been demonstrated to correctly identify bacteria from spectra originating at different laboratories [5], however, this approach is currently suffering from an incomplete protein database for many of the organisms that are of interest. As the proteomic database becomes more populated with organisms of concern, this approach will become more feasible for bacterial identification, at

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Analysis of Microbial Mixtures by Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry

Cited by 124 publications

References 10 publications

Rapid Identification of Bacteria from Positive Blood Culture Bottles by Use of Matrix-Assisted Laser Desorption-Ionization Time of Flight Mass Spectrometry Fingerprinting

Rapid Identification of Bacteria from Positive Blood Culture Bottles by Use of Matrix-Assisted Laser Desorption-Ionization Time of Flight Mass Spectrometry Fingerprinting

Rapid Identification of Staphylococci Isolated in Clinical Microbiology Laboratories by Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry

Bacterial analysis by MALDI-TOF mass spectrometry: An inter-laboratory comparison

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