Application Of MALDI-TOF MS Research Articles

Application of MALDI-TOF MS to assess clinical characteristics, risk factors, and outcomes associated with anaerobic bloodstream infection: a retrospective observational study

BackgroundCorrectly identifying anaerobic bloodstream infections (BSIs) is difficult. However, a new technique, matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS), enables more accurate identification and appropriate treatment. Anaerobic BSIs identified by MALDI-TOF MS were retrospectively analyzed to determine the clinical and microbiological features and patient outcomes based on the anaerobic genera or group.MethodsMedical records of patients with anaerobic BSIs were used to conduct a single-center retrospective cohort study from January 2016 to December 2020 in Nagoya, Japan. Multivariate logistic regression analysis was performed to determine the independent risk factors for in-hospital mortality.ResultsOf the 215 patients with anaerobic BSIs, 31 had multiple anaerobic organisms in the blood culture, including 264 total episodes of anaerobic BSIs. Bacteroides spp. were isolated the most (n = 74), followed by gram-positive non-spore-forming bacilli (n = 57), Clostridium spp. (n = 52), gram-positive anaerobic cocci (GPAC) (n = 27), and gram-negative cocci (n = 7). The median patient age was 76 years; 56.7% were male. The most common focal infection site was intra-abdominal (36.7%). The in-hospital mortality caused by anaerobic BSIs was 21.3%, and was highest with Clostridium spp. (36.5%) and lowest with GPAC (3.7%). Age, solid tumors, and Clostridium spp. were independent risk factors for in-hospital mortality.ConclusionsWe identified current anaerobic BSI trends using MALDI-TOF MS and reported that mortality in patients with anaerobic BSIs patients was highest with Clostridium spp. infections.

Application of MALDI-TOF MS Profiling Coupled With Functionalized Magnetic Enrichment for Rapid Identification of Pathogens in a Patient With Open Fracture.

Posttraumatic infections can occur in orthopedic trauma patients, especially in open fractures. Rapid and accurate identification of pathogens in orthopedic trauma is important for clinical diagnosis and antimicrobial treatment. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has been successfully used for first-line identification of pathogens grown on culture plates. However, for direct analysis of liquid clinical specimens, pre-purification of the sample is necessary. Herein, we investigated the feasibility of coupling Fc-MBL@Fe3O4 enrichment with MALDI-TOF MS profiling in the identification of pathogens in liquid-cultured samples. This method is successfully used for the identification of pathogens in a patient with an open-leg fracture obtained at sea. Pathogens were enriched by Fc-MBL@Fe3O4 from briefly pre-cultured liquid media and identified by MALDI-TOF MS. We identified an opportunistic pathogen, Vibrio alginolyticus, which is uncommon in clinical orthopedic trauma infection but exists widely in the sea. Therefore, combining Fc-MBL@Fe3O4 enrichment and MALDI-TOF MS profiling has great potential for direct identification of microbes in clinical samples.

MALDI-TOF mass spectrometry–based identification of Eurotiales from different substrates and locations in Brazil

We used matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) fingerprinting to identify 95 strains of Aspergillus, Penicillium, and Talaromyces isolated from soil, marine sediment, and plants in Brazil. Samples for mass spectrometry were composed of conidia and conidiophores directly applied to the target plate and co-crystallized with the matrix solution. Cluster analyses of MS data and phylogenetic analyses based on the second largest subunit of RNA polymerase II gene sequence (RPB2) supported the identification of 42 species in Aspergillus (n = 17), Penicillium (n = 16), and Talaromyces (n = 9). In few cases, MALDI-TOF dendrograms split strains from one species into two neighboring clusters, but strains from different species were never grouped together. Three Penicillium species delimited by MALDI-TOF MS did not correspond to known species present in the large RPB2 dataset available for this group and may represent new taxa. These results expand the scope of applications of MALDI-TOF MS to the task of screening phylogenetically diverse assemblages of morphologically similar strains derived from field collections, allowing for fast discrimination of common and rare species, and detection of possible new taxa.

Identification of ovine-associated staphylococci by MALDI-TOF mass spectrometry

AbstractThe objective of this study was to use matrix-assisted laser desorption ionisation–time of flight mass spectrometry (MALDI-TOF MS) for the identification of ovine-associated staphylococci. Presumptive Staphylococcus isolates were recovered from ovine udder surface (US), individual raw milk, bulk tank milk, and cheese samples and were characterised by conventional phenotypic methods. A total of 69 bacterial isolates were further confirmed by MALDI-TOF MS. Forty-two (60.9%) of 69 isolates were successfully identified on genus and species level. Two thirds (n = 28) of the 42 identified isolates were shown to be Staphylococcus spp. These 28 staphylococcal isolates formed two clusters, one consisting of 22 Staphylococcus aureus strains and the other composed of 6 non-aureus staphylococci, including S. simulans (n = 3), S. auricularis, S. equorum, and S. haemolyticus. MALDI-TOF MS has proven to be a reliable tool for the identification of staphylococci from raw sheep's milk, especially bulk tank milk; however, currently it appears to be less useful for the identification of bacterial isolates originating from ovine US samples. This is the first study to evaluate the applicability of MALDI-TOF MS for identification of Staphylococcus spp. in ovine raw milk, cheese, and US samples in Hungary.

Application of MALDI-TOF MS for Rapid Identification of Microorganisms in Food Microbiology

Application of MALDI-TOF MS for Rapid Identification of Microorganisms in Food Microbiology

Evaluation of MALDI-ToF Mass Spectrometry for Rapid Detection of Cereulide From Bacillus cereus Cultures.

Bacillus cereus plays an often unrecognized role in food borne diseases. Food poisoning caused by this pathogen is manifested by either diarrhea or emesis. Due to the relatively high prevalence of emetic toxin cereulide associated food poisoning, methods for simple and reliable detection of cereulide producing strains are of utmost importance. Recently, two different studies reported on the application of MALDI-ToF MS for either the differentiation of emetic and non-emetic strains of B. cereus or for direct detection of cereulide from bacterial colony smears. However, for implementation of cereulide detection using MALDI-ToF MS in routine microbiological diagnostics additional investigations on the sensitivity and specificity as well as on the fitting into common workflows for bacterial identification are needed. These aspects prompted us to investigate open issues and to test sample preparation methods, commonly used for microbial identification for their suitability to detect the emetic toxin from bacteria. Based on our experimental findings we propose a workflow that allows identification of B. cereus and sensitive detection of cereulide in parallel, using linear-mode MALDI-ToF MS equipment. The protocol was validated in a blinded study and is based on the well-established ethanol/formic acid extraction method. Cereulide is detected in the ethanol wash solution of samples identified as B. cereus as peaks at m/z 1175 and 1191. Peak position difference of 16 Th (Thomson) indicates detection of the sodium and potassium adducts of cereulide. This sample treatment offers possibilities for further characterization by more sophisticated LC-MS-based methods. In summary, the ease of use and the achieved level of analytical sensitivity as well as the wide-spread availability of MALDI-ToF MS equipment in clinical microbiological laboratories provides a promising tool to improve and to facilitate routine diagnostics of B. cereus associated food intoxications.

MALDI-TOF MS - application in food microbiology.

Microbiological purity control of food products is of great importance in the food industry. Contaminated food is often characterized by a deteriorated taste, smell, and appearance, and when consumed, it can pose a threat to human health and life. Also, contamination incurs huge financial losses to the food industry. Different methods are used for identification of the microorganisms isolated from food, which are based on phenotypic, immunologic, genetic, and spectroscopic techniques. Unfortunately, these methods have the following disadvantages: laborious, time-consuming, requiring a well-trained spectrometer operator with specialist knowledge, or very accurate, but complicated, and extremely expensive. In recent years, matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) has been gaining increasing importance in the field of food microbiology. Unlike other techniques used for microorganisms identification, MALDI-TOF MS is more rapid, accurate and cost-efficient, and easy to perform. Thus, this method can be applied in the food industry to quickly and accurately identify microorganisms, which is crucial for controlling the quality of food products. The present review aims to discuss the selected applications of MALDI-TOF MS in food microbiology. It mainly focuses on the characteristics of this method and its potential use in the identification and typing of microorganisms including filamentous fungi, yeasts, and bacteria in fermented beverages (beer and wine), honey, dairy products like yogurt and pasteurized milk, pork, and seafood.

Utility of MALDI-TOF MS for differentiation of Neisseria gonorrhoeae isolates with dissimilar azithromycin susceptibility profiles.

Antibiotic-resistant gonorrhoea has been a chronic public health burden since the mid-1930s. Recent emergence of isolates resistant to the current recommended antibiotics for gonorrhoea further magnifies the threat of untreatable gonorrhoea. The lack of new, effective antibiotics highlights the need for better understanding of the population structure of Neisseria gonorrhoeae in order to provide greater insight on how to curtail the spread of antimicrobial-resistant N. gonorrhoeae. To explore a potential application of MALDI-TOF MS to differentiate N. gonorrhoeae displaying different levels of susceptibility to the antibiotic azithromycin. We conducted MALDI-TOF MS using the Bruker Biotyper on 392 N. gonorrhoeae isolates collected through the Gonococcal Isolate Surveillance Project (GISP) and/or the Strengthening the United States Response to Resistant Gonorrhea (SURRG) project. The MALDI-TOF MS spectra were visually analysed to assess the presence of distinctive peak(s). Statistical analysis was performed to assess the relationship between gonococcal isolates with the distinct protein peak and antibiotic susceptibility. In this study, we were able to differentiate N. gonorrhoeae isolates into two distinct subpopulations using MALDI-TOF MS. Isolates were distinguished by the presence or absence of a spectral peak at 11 300 Da. Notably, these two groups exhibited different levels of susceptibility to azithromycin. We have shown that in addition to its ability to identify N. gonorrhoeae, MALDI-TOF MS could also be used to differentiate gonococcal isolates with different levels of susceptibility to azithromycin.

Fast and High-Throughput Evaluation of Photodynamic Effect by Monitoring Specific Protein Oxidation with MALDI-TOF Mass Spectrometry.

In antibacterial practices by photodynamic treatment, bacteria are incubated with photosensitizers and then oxidized to death by generating reactive oxygen species (ROS) under light irradiation. Generally, Luria-Bertani (LB) agar colony is a conventional method to evaluate the photodynamic effect. However, this method is time consuming, easily disturbed by pollutants, and limited to the analysis of a pure bacteria sample. Herein, we introduce a novel method of photodynamic effect evaluation through in situ detection of specific protein oxidation by matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) with only 1 μL of sample in a fast (less than 1 min per sample) and high-throughput (up to 384 samples per run) way. The oxidation rates of specific proteins stayed highly consistent with bactericidal rates and thus MALDI-TOF MS might be able to replace the LB agar colony to evaluate the photodynamic effect. With the present method, several experimental conditions including different photosensitizer types, dosage controls, and different illumination times were easily screened to optimize photodynamic effect. Photodynamic effects of various bacteria species, cancer cells, and even mixture samples were also evaluated. The results demonstrate the promising application of MALDI-TOF MS in evaluating the photodynamic effect of each component in a mixture sample without any separation or purification, which could not be achieved by the traditional LB agar colony method.

Testing the Applicability of MALDI-TOF MS as an Alternative Stock Identification Method in a Cryptic Species Complex.

Knowledge of intraspecific variability of a certain species is essential for their long-term survival and for the development of conservation plans. Nowadays, molecular/genetic methods are the most frequently used for this purpose. Although, the Matrix Assisted Laser Desorption Ionization Time of Flight Mass Spectrometry (MALDI-TOF MS) technique has become a promising alternative tool to specify intraspecific variability, there is a lack of information about the limitations of this method, and some methodological issues need to be resolved. Towards this goal, we tested the sensitivity of this method on an intraspecific level, using genetically identified individuals of a cryptic fish species complex collected from five distinct populations. Additionally, some methodologic issues, such as the effect of (1) delayed sample preparation, (2) clove oil anaesthetization, and (3) different tissue types (muscle, and brain) were investigated using the MS analysis results. Our results show that the delayed sample preparation has a fundamental effect on the result of MS analysis, while at the same time the clove oil did not affect the results considerably. Both the brain and muscle samples were usable for cryptic species identification, but in our opinion this method has limited applicability for population-level segregation. The application of MALDI-TOF MS to the exploitable toolkit of phylogenetic and taxonomic researches could be used to broaden conclusions.

Applicability of MALDI-TOF MS for determination of quinolone residues in fish.

MALDI-TOF MS approach for determination of six quinolones residues in fillets of pangasius (Pangasionodon hypophthalmus) was studied, considering that is a very sensitive analytical technique with simple and high-throughput operation, contributing to knowledge regarding application of this technique to the determination of small-molecular-weight organic compound residues in foods. LIFT-MS/MS showed to be a successful approach to identify the presence of all quinolone residues in the fish fillet, at their respective MRL level. This study opens an important field of research for the development of simple and high-throughput bioanalytical screening methods for the determination of veterinary drug residues in foods.

Application of MALDI-TOF MS to rapid identification of anaerobic bacteria

BackgroundMatrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) has been rapidly developed and widely used as an analytical technique in clinical laboratories with high accuracy in microorganism identification.ObjectiveTo validate the efficacy of MALDI-TOF MS in identification of clinical pathogenic anaerobes.MethodsTwenty-eight studies covering 6685 strains of anaerobic bacteria were included in this meta-analysis. Fixed-effects models based on the P-value and the I-squared were used for meta-analysis to consider the possibility of heterogeneity between studies. Statistical analyses were performed by using STATA 12.0.ResultsThe identification accuracy of MALDI-TOF MS was 84% for species (I2 = 98.0%, P < 0.1), and 92% for genus (I2 = 96.6%, P < 0.1). Thereinto, the identification accuracy of Bacteroides was the highest at 96% with a 95% CI of 95–97%, followed by Lactobacillus spp., Parabacteroides spp., Clostridium spp., Propionibacterium spp., Prevotella spp., Veillonella spp. and Peptostreptococcus spp., and their correct identification rates were all above 90%, while the accuracy of rare anaerobic bacteria was relatively low. Meanwhile, the overall capabilities of two MALDI-TOF MS systems were different. The identification accuracy rate was 90% for VITEK MS vs. 86% for MALDI biotyper system.ConclusionsOur research showed that MALDI-TOF-MS was satisfactory in genus identification of clinical pathogenic anaerobic bacteria. However, this method still suffers from different drawbacks in precise identification of rare anaerobe and species levels of common anaerobic bacteria.

Application of MALDI-TOF MS to species complex differentiation and strain typing of food related fungi: Case studies with Aspergillus section Flavi species and Penicillium roqueforti isolates

Filamentous fungi are one of the main causes of food losses worldwide and their ability to produce mycotoxins represents a hazard for human health. Their correct and rapid identification is thus crucial to manage food safety. In recent years, MALDI-TOF emerged as a rapid and reliable tool for fungi identification and was applied to typing of bacteria and yeasts, but few studies focused on filamentous fungal species complex differentiation and typing. Therefore, the aim of this study was to evaluate the use of MALDI-TOF to identify species of the Aspergillus section Flavi, and to differentiate Penicillium roqueforti isolates from three distinct genetic populations. Spectra were acquired from 23 Aspergillus species and integrated into a database for which cross-validation led to more than 99% of correctly attributed spectra. For P. roqueforti, spectra were acquired from 63 strains and a two-step calibration procedure was applied before database construction. Cross-validation and external validation respectively led to 94% and 95% of spectra attributed to the right population. Results obtained here suggested very good agreement between spectral and genetic data analysis for both Aspergillus species and P. roqueforti, demonstrating MALDI-TOF applicability as a fast and easy alternative to molecular techniques for species complex differentiation and strain typing of filamentous fungi.

Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry for the Rapid Detection of Antimicrobial Resistance Mechanisms and Beyond.

Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) has been successfully applied in recent years for first-line identification of pathogens in clinical microbiology because it is simple to use, rapid, and accurate and has economic benefits in hospital management. The range of clinical applications of MALDI-TOF MS for bacterial isolates is increasing constantly, from species identification to the two most promising applications in the near future: detection of antimicrobial resistance and strain typing for epidemiological studies. The aim of this review is to outline the contribution of previous MALDI-TOF MS studies in relation to detection of antimicrobial resistance and to discuss potential future challenges in this field. Three main approaches are ready (or almost ready) for clinical use, including the detection of antibiotic modifications due to the enzymatic activity of bacteria, the detection of antimicrobial resistance by analysis of the peak patterns of bacteria or mass peak profiles, and the detection of resistance by semiquantification of bacterial growth in the presence of a given antibiotic. This review provides an expert guide for MALDI-TOF MS users to new approaches in the field of antimicrobial resistance detection, especially possible applications as a routine diagnostic tool in microbiology laboratories.

MALDI-TOF MS Applications to the Detection of Antifungal Resistance: State of the Art and Future Perspectives.

MALDI-TOF MS technology has made possible revolutionary advances in the diagnosis of infectious diseases. Besides allowing rapid and reliable identification of bacteria and fungi, this technology has been recently applied to the detection of antimicrobial resistance. Several approaches have been proposed and evaluated for application of MALDI-TOF MS to antimicrobial susceptibility testing of bacteria, and some of these have been or might be applied also to yeasts. In this context, the comparison of proteomic profiles of bacteria/yeasts incubated with or without antimicrobial drugs is a very promising method. Another recently proposed MALDI-TOF MS-based approach for antifungal susceptibility testing is the application of the semi-quantitative MALDI Biotyper antibiotic susceptibility test rapid assay, which was originally designed for antimicrobial susceptibility testing of bacteria, to yeast isolates. Increasingly effective and accurate MS tools and instruments as well as the possibility to optimize analytical parameter settings for targeted applications have generated an expanding area in the field of clinical microbiology diagnostics, paving the way for the development and/or optimization of rapid methods for antifungal susceptibility testing in the near future. In the present study, the state of the art of MALDI-TOF MS applications to antifungal susceptibility testing is reviewed, and cutting-edge developments are discussed, with a particular focus on methods allowing rapid detection of drug resistance in pathogenic fungi causing systemic mycoses.

A label-free MALDI TOF MS-based method for studying the kinetics and inhibitor screening of the Alzheimer's disease drug target β-secretase.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI TOF MS) is a well-established method with a unique set of qualities including sensitivity, minute sample consumption, and label-free detection, all of which are highly desired in enzyme assays. On the other hand, the application of MALDI TOF MS is usually limited by high concentrations of MS-incompatible compounds in the reaction mixture such as salts or organic solvents. Here, we introduce kinetic and inhibition studies of β-secretase (BACE1), a key enzyme of the progression of Alzheimer's disease. Compatibility of the enzyme assay with MALDI TOF MS was achieved, providing both a complex protocol including a desalting step designed for rigorous kinetic studies and a simple mix-and-measure protocol designed for high-throughput inhibitor screening. In comparison with fluorescent or colorimetric assays, MALDI TOF MS represents a sensitive, fast, and label-free technique with minimal sample preparation. In contrast to other MS-based methodological approaches typically used in drug discovery processes, such as a direct injection MS or MS-coupled liquid chromatography or capillary electrophoresis, MALDI TOF MS enables direct analysis and is a highly suitable approach for high-throughput screening. The method's applicability is strongly supported by the high correlation of the acquired kinetic and inhibition parameters with data from the literature as well as from our previous research. Graphical abstract ᅟ.

Application of MALDI-TOF MS in identification of clinical Aspergillus

Objective To discuss the application of matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS) in the identification of Aspergillus and evaluate its performance. Methods the clinical isolates of Aspergillus collected from May 2017 to March 2018 in PLA General Hospital were identified by VITEK MS V3.0 and the results were analyzed. The ITS sequencing resultswere used as the gold standard. Results It identified 9 Aspergillus species (including 12 Aspergillus species in total) through the V3.0 database, accounting for 86.24% of the total clinical isolates. The identification rate by VITEK MS was 91.49% with 16.51% was not identified. The coincidence rate of genus was 93.62%, of which only two Aspergillus versicolor were identified to the level of the genus. According to the confidence level analysis, 88.30% of the strains obtained more than 99% of the identification rate. 13.83% of the strains did not have the identification results for the first time, with the error rate of 3.19%. After secondary extractions, the percentage of unidentified strain was reduced to 6.38%, and the identification error rate was reduced to 2.13%. Combined with traditional identification and VITEK MS identification, the correct rate of strains identification was 98.94% on genus level, and was 93.62% on species level. The influence of other fungi on Aspergillus identification was 0%. Conclusion As a powerful supplement to the traditional identification method, MALDI-TOF MS showed a lot of convenience when applied in the identification of Aspergillus, which improves the identification accuracy and the identification ability for fungi in laboratory.(Chin J Lab Med, 2018, 41: 577-582) Key words: Aspergillus; Mycological typing techniques; Spectrometry, mass, matrix-assisted laser desorption-ionization

The challenge of MALDI-TOF MS technique in clinical microbiological diagnosis and application

MALDI-TOF MS is a revolutionary and innovative technologyin clinical microbiological diagnosis. Due to its advantages of speed, specificity and ease of operation, MALDI-TOF MS has been rapidly accepted and approved by clinical laboratory. However, many challenges appeared when applied in clinical application. For example, sample preparation needs to be further optimized. Identification techniques have limitations. The quality improvement of database and the diversity of microbial species are still under discussion.The application of antimicrobial susceptibility testing is still controversial.The way ofrare identification resultstransmitting into clinical treatment is still being explored. But the application of MALDI-TOF MS in clinical microbiological diagnosis still needs to be improved.(Chin J Lab Med, 2018, 41: 559-562) Key words: Spectrometry, mass, matrix-Assisted laser desorption-ionization; Microbiological techniques; Clinical laboratory techniques

Development and application of MALDI-TOF MS for identification of food spoilage fungi

Filamentous fungi are frequently involved in food spoilage and cause important food losses and substantial economic damage. Their rapid and accurate identification is a key step to better manage food safety and quality. In recent years, MALDI-TOF MS has emerged as a powerful tool to identify microorganisms and has successfully been applied to the identification of filamentous fungi especially in the clinical context. The aim of this study was to implement a spectral database representative of food spoilage molds. To this end, after application of a standardized extraction protocol, 6477 spectra were acquired from 618 fungal strains belonging to 136 species and integrated in the VITEK MS database. The performances of this database were then evaluated by cross-validation and ∼95% of correct identification to the species level was achieved, independently of the cultivation medium and incubation time. The database was also challenged with external isolates belonging to 52 species claimed in the database and 90% were correctly identified to the species level. To our best knowledge, this is the most comprehensive database of food-relevant filamentous fungi developed to date. This study demonstrates that MALDI-TOF MS could be an alternative to conventional techniques for the rapid and reliable identification of spoilage fungi in food and industrial environments.

Application of MALDI-TOF MS for the subtyping of Arcobacter butzleri strains and comparison with their MLST and PFGE types

For the first time, this study evaluated the use of MALDI-TOF as a typing tool for Arcobacter butzleri. A total of 104 A. butzleri strains isolated from different sources in an artisanal dairy plant in Italy were identified and typed using MALDI-TOF and compared with their multilocus sequence typing (MLST) and pulsed field gel electrophoresis (PFGE) profiles found in previous studies. MALDI-TOF correctly identified all the isolates to species level. No clearly delineated clusters appeared on dendrograms based on either the complete spectra or the significant peaks, but nine clusters were defined using the cophenetic correlation. Interestingly, MALDI-TOF proved able to discriminate A. butzleri strains below species level, confirming its potential use for epidemiological surveys. As expected, the comparative analysis with PFGE and MLST showed that the discriminatory index was lower for MALDI-TOF but roughly comparable to sequence types and pulsotypes. MALDI-TOF appears to be a relatively low cost answer to the urgent need for more rapid, less expensive typing tools suitable for source attribution studies, readily allowing multiple typing methods to be combined. This study provides insights into MALDI-TOF as potential epidemiological tool. Its application in healthcare surveillance systems awaits further exploration to encourage interaction and convergence studies between primary care in humans and animal and food veterinary authorities as part of the One Health concept.