MALDI-TOF Mass Spectrometry For Identification Research Articles

Epidemiology and management of tinea capitis in France: A 6-year nationwide retrospective survey.

Tinea capitis (TC) is still a frequent dermatophytosis in France, both autochthonous and imported. A nationwide retrospective survey was performed and a total of 4395 TC cases were recorded within 36 French mycology laboratories during a 6-year period. TC is a disease that occurs in childhood with 85% of the cases occurring before 10 years old and 94% before the age of 15. Anthropophilic origin was predominant with 779 cases of Trichophyton tonsurans (32.6%), 738 cases of Trichophyton soudanense/T. violaceum (31%), and 445 cases of Microsporum audouinii (19.2%). Of note, T. tonsurans represents more than 80% of the cases in the French West Indies (Martinique and Guadeloupe). By contrast, zoophilic species were less prevalent with mainly M. canis (10.3%) confirming the shift from zoophilic to anthropophilic species observed in many centers during the last decades. During this survey, diagnosis methods were also collected. Most labs had a classical process for the diagnosis: microscopic direct examination associated to cultures on Sabouraud and Sabouraud-cycloheximide media (incubated between 25±5°C for at least 3 weeks) in all laboratories. Identification of the causal dermatophyte was performed by microscopic and macroscopic examination of the cultures in 100% of the labs, with various specific culture media available when fructification was insufficient (mainly malt or potato-dextrose agar, or Borelli medium). New techniques were also implemented with the introduction of MALDI-TOF mass spectrometry identification in more than two third of the labs, and molecular identification available if necessary in half of the labs.

MALDI-TOF mass spectrometry identification and antifungal susceptibility testing of yeasts causing vulvovaginal candidiasis (VVC) in Tebessa (Northeastern Algeria).

Vulvovaginal candidiasis (VVC) alongside with antifungal resistance are becoming a major clinical problem in recent years. A prospective study aimed to evaluate the diversity of yeast strains associated with VVC in Tebessa city (northeastern Algeria) and investigate their susceptibility patterns. Over two months, yeasts were isolated on chromogenic medium from twenty-nine non-pregnant women with symptomatic VVC. The isolates were characterized with MALDI-TOF MS and antifungal susceptibility testing was performed for nine antifungal drugs using SensititreTM YeastOneTM YO10. Twenty-nine non-duplicate yeasts were recovered and the mass spectrometry profiles showed reliable scores of which four genera and five different species were identified. Candida albicans accounted for 65.5 % (n = 19) of the total number of isolates, followed by C. glabrata with 20.7% (n = 6). For the remaining non-albicans Candida (NCA) species, Kluyveromyces marxianus with 6.9% (n = 2), Pichia kudriavzevii and Saccharomyces cerevisiae with one isolate each. The antifungal susceptibilities showed wild type MICs of C. albicans to amphotericin B, azoles and echinocandins. In addition, four C. albicans isolates were resistant to flucytosine. For C. glabrata isolates, 100% non-WT phenotype was found for both posaconazole and itraconazole. For the very first time, the obtained outcomes bring out new data concerning the epidemiology of yeasts causing VVC in Algeria and their antimicrobial susceptibility profiles.

Assessment of the main pathogens associated with clinical and subclinical endometritis in cows by culture and MALDI-TOF mass spectrometry identification

Clinical endometritis (CE) and subclinical endometritis (SCE) are diseases that affect dairy cows during the puerperium, causing negative effects on the animals' milk production and fertility. The objective of this study was to assess the main bacteria related to cases of CE and SCE from uterine samples of dairy cows in Brazilian herds. Selective and differential media were used for isolation of aerobic and anaerobic bacteria and further MALDI-TOF mass spectrometry (MS) identification. A total of 279 lactating dairy cows with 28 to 33 d in milk from 6 commercial farms were evaluated. Initially, cows were classified in 3 groups: cytologic healthy cows (n = 161), cows with CE (n = 83), and cows with SCE (n = 35). Healthy animals presented 97 species, followed by the CE group with 53 identified species, and SCE cows presented only 21 bacterial species. We found a significantly higher isolation rate of Trueperella pyogenes in CE (26.5%) cows compared with healthy and SCE cows. Some anaerobic species were exclusively isolated from the CE group, even though they presented lower frequency. Interestingly, 18.1% of samples from CE cows and 40% of SCE cows were negative to bacterial isolation. Despite the use of culture-dependent methods instead of molecular methods, the present study enabled the identification of a complex community of 127 different species from 48 genera, composed of aerobic and anaerobic bacterial species among the 3 different animal groups. The method of sample collection, culture, and identification by MALDI-TOF MS were essential for the success of the analyses.

MALDI-TOF mass spectrometry identification of mosquitoes collected in Vietnam

BackgroundMatrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is a tool that has revolutionised clinical microbiology and has recently been described as an innovative and effective approach to arthropod identification.MethodsIn this study, mosquitoes were captured in Vietnam using four different methods (human landing catch, CDC light traps, BG-Sentinel traps, animal-baited net traps). A total of 4215 mosquitoes were captured and morphologically identified as belonging to three genera: Aedes, Anopheles and Culex. We randomly selected 1253 mosquitoes, including 662 specimens of 14 Anopheles species, 200 specimens of two Aedes species and 391 morphologically unidentified Culex specimens, for molecular and MALDI-TOF MS analysis. The DNA from 98 mosquitoes (69 Anopheles specimens, 23 Culex specimens and six Aedes sp. specimens) was subjected to molecular analysis, either to confirm our morphological identification or the MALDI-TOF MS results, as well as to identify the Culex species that were morphologically identified at the genus level and to resolve the discrepancies between the morphological identification and the MALDI-TOF MS identification.ResultsHigh-quality MS spectra were obtained for 1058 of the 1253 specimens (84%), including 192/200 for Aedes, 589/662 for Anopheles and 277/391 for Culex. The blind test showed that 986/997 (99%) of the specimens were correctly identified by MALDI-TOF MS, with log score values ranging from 1.708 to 2.843. Eleven specimens of Culex could not be identified based on morphological features, MALDI-TOF MS or molecular analysis.ConclusionsThis study enabled us to identify several species of mosquitoes from Vietnam using MALDI-TOF MS, and to enrich our database of MALDI-TOF MS reference spectra.Graphical

MALDI-TOF Mass Spectrometry as a Rapid Screening Alternative for Non-tuberculous Mycobacterial Species Identification in the Veterinary Laboratory.

Non-tuberculous mycobacteria (NTM) are difficult to identify by biochemical and genetic methods due to their microbiological properties and complex taxonomy. The development of more efficient and rapid methods for species identification in the veterinary microbiological laboratory is, therefore, of great importance. Although MALDI-TOF Mass Spectrometry (MS) has become a promising tool for the identification of NTM species in human clinical practise, information regarding its performance on veterinary isolates is scarce. This study assesses the capacity of MALDI-TOF MS to identify NTM isolates (n = 75) obtained from different animal species. MALDI-TOF MS identified 76.0% (n = 57) and 4% (n = 3) of the isolates with high and low confidence, respectively, in agreement with the identification achieved by Sanger sequencing of housekeeping genes (16S rRNA, hsp65, and rpoB). Thirteen isolates (17.3%) were identified by Sanger sequencing to the complex level, indicating that these may belong to uncharacterised species. MALDI-TOF MS approximated low confidence identifications toward closely related mycobacterial groups, such as the M. avium or M. terrae complexes. Two isolates were misidentified due to a high similarity between species or due to the lack of spectra in the database. Our results suggest that MALDI-TOF MS can be used as an effective alternative for rapid screening of mycobacterial isolates in the veterinary laboratory and potentially for the detection of new NTM species. In turn, Sanger sequencing could be implemented as an additional method to improve identifications in species for which MALDI-TOF MS identification is limited or for further characterisation of NTM species.

Fast antibiotic susceptibility testing of urine microflora using a microbiological analyzer based on coherent fluctuation nephelometry.

Traditional culture-based microbiological methods remain the most used for defining the etiology of urinary tract infections and antibiotic susceptibility testing (AST) of isolated uropathogens. They are time-consuming and lead to delays of several days when obtaining the final results of microbiological tests. In this study, we validate the possibility of using a microbiological CFN analyzer combined with MALDI-TOF mass spectrometry (MS) for fast conclusive urine testing (1day) without obtaining pure cultures. The study included three stages: detection of urine microflora growth using the CFN analyzer to separate positive and negative samples within 2-4h; fast MS identification of positive samples without isolating uropathogens; fast AST using CFN analyzer within 3-6h. In parallel, all urine samples were tested by traditional culture-based microbiological methods. In total, 194 urine samples were tested, and 22 urine cultures were identified by MS, among them, 20 monocultures with bacterial counts ≥ 105 and 2 mixed cultures. The AST of these 22 urine cultures and additional 88 pure clinical cultures was performed using eight antibiotics. Overall, 276 tests were performed. The results of AST obtained using the CFN analyzer and traditional methods were in good agreement (98.2%). Although two mixed cultures were falsely identified as monocultures, their susceptibility determined by the CFN analyzer was correct. The CFN analyzer is promising and effective for fast AST. Combined with MS identification, it allows to perform full urine analysis in 1day without the lengthy isolation of pure cultures.

Anti-Staphylococcal Activity of Cinnamomum zeylanicum Essential Oil against Planktonic and Biofilm Cells Isolated from Canine Otological Infections.

The aim of this study was to evaluate the phytochemical profile of Cinnamomum zeylanicum essential oil (CZEO) and their antimicrobial and antibiofilm activity against Staphylococcus strains isolated from canine otitis. First, the CZEO chemical composition was determined by gas chromatography-mass spectrometry (CG-MS). External otitis samples collected from dogs were submitted to staphylococcal isolation, followed by MALDI-TOF mass spectrometry identification. The antimicrobial action was tested against the isolates using the disk-diffusion and microdilution methods. The antibiofilm activity was evaluated by CZEO-based concentrations, subMIC for biofilm formation and supraMIC against preformed biofilm, quantified by crystal violet (CV) staining and CFU counting. The chemical analysis revealed that (E)-cinnamaldehyde, eugenol and (E)-cinnamyl acetate were the main compounds in the CZEO, representing 77.42, 8.17 and 4.50%, respectively. Two strains of three different species, S. saprophyticus, S. schleiferi and S. pseudintermedius, were identified. The disk-diffusion test showed an inhibitory zone diameter, ranging from 34.0 to 49.5 mm, while the MIC and MBC values were around 500 and 1000 µg/mL. SubMIC demonstrated an inhibition on biofilm formation against 4 out the 6 strains tested. On mature biofilm, the CZEO-based supraMIC groups had slightly change on biomass, however, the biofilm cell viability decreased the CFU in 3 magnitude orders.

Dysregulated Tear Film Proteins in Macular Edema Due to the Neovascular Age-Related Macular Degeneration Are Involved in the Regulation of Protein Clearance, Inflammation, and Neovascularization.

Macular edema and its further complications due to the leakage from the choroidal neovascularization in course of the age-related macular degeneration (AMD) is a leading cause of blindness among elderly individuals in developed countries. Changes in tear film proteomic composition have been reported to occur in various ophthalmic and systemic diseases. There is an evidence that the acute form of neovascular AMD may be reflected in the tear film composition. Tear film was collected with Schirmer strips from patients with neovascular AMD and sex- and age-matched control patients. Two-dimensional electrophoresis was performed followed by MALDI-TOF mass spectrometry for identification of differentially expressed proteins. Quantitative analysis of the differential electrophoretic spots was performed with Delta2D software. Altogether, 11 significantly differentially expressed proteins were identified; of those, 8 were downregulated, and 3 were upregulated in the tear film of neovascular AMD patients. The differentially expressed proteins identified in tear film were involved in signaling pathways associated with impaired protein clearance, persistent inflammation, and neovascularization. Tear film protein analysis is a novel way to screen AMD-related biomarkers.

Nano-etched fused-silica capillary used for on-line preconcentration and electrophoretic separation of bacteriophages from large blood sample volumes with off-line MALDI-TOF mass spectrometry identification.

The properties of staphylococcal phages from the Siphoviridae, Podoviridae, and Myoviridae families were monitored using capillary electrophoretic methods on fused-silica capillaries with different morphology of surface roughness. Isoelectric points of the examined phages were determined by capillary isoelectric focusing in the original, smooth fused-silica capillary, and they ranged from 3.30 to 3.85. For capillary electrophoresis of phages, fused-silica capillaries with the "pock" and "cone" roughened surface types were prepared by etching a part of the capillary with supercritical water. The best resolution of the individual phages (to range from 3.2 to 4.6) was achieved with the "cone" surface-type fused-silica capillary. Direct application of phage K1/420 at the infection site, represented by human plasma or full blood spiked with Staphylococcus aureus, was on-line monitored by micellar electrokinetic chromatography. The phage particles were dynamically adhered onto the roughened surface of the capillary from 10μL of the prepared sample at the optimized flow rate of 6.5μLmin-1. The limit of detection was determined to be 104 phage particles. The linearity of the calibration lines was characterized by the regression coefficient, R2 =0.998. The relative standard deviation (RSD) of the peak area, calculated from ten independent measurements, was (±) 2%. After analysis, viability of the detected phages was verified by the modified "double-layer drop assay" method, and collected phage fractions were simultaneously off-line analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Graphical abstract.

Evaluation of Human Milk Microbiota by 16S rRNA Gene Next-Generation Sequencing (NGS) and Cultivation/MALDI-TOF Mass Spectrometry Identification.

The aim of the present study was to characterize human milk microbiota (HMM) with 16S rRNA gene amplicon next-generation sequencing and cultivation/matrix-assisted laser desorption/ionization (MALDI)-time of flight (TOF) mass spectrometry (MS) identification approaches. We analyzed 31 human milk samples from healthy Slovenian mothers. To check the accuracy of MALDI-TOF MS identification, several colonies representing most abundant genera and those, which could not be reliably identified by MALDI-TOF, were subjected to Sanger sequencing of their 16S rRNA gene. We showed that cultivation/MALDI-TOF MS was a suitable tool for culture-dependent determination of HMM. With both approaches, Staphylococcus and Streptococcus were found as predominant genera in HMM and the abundance of Staphylococcus was associated with decreased microbial diversity. In addition, we characterized factors that might influence HMM. The use of a breast pump was significantly associated with composition of HMM, higher microbial load, and lower abundance of cultivable staphylococci. Moreover, our study suggests that administration of probiotics to the suckling infant might influence HMM by increased abundance of lactobacilli and the presence of viable probiotic bacteria in human milk. However, since our study was observational with relatively small sample size, more targeted studies are needed to study possible transfer of probiotics to the mammary gland via an external route and the physiological relevance of these events.

APPLICATION OF MALDI-TOF MASS SPECTROMETRY FOR IDENTIFICATION OF BACTERIA ISOLATED FROM TRADITIONAL SLOVAK CHEESE “PARENICA”

In this study, the cultivable population of bacteria from a traditional Slovak cheese “Parenica” made from cow milk were identified using MALDI-TOF mass spectrometry (MS). A total of 100 “Parenica” cheese packages from four producers were examined, including n=50 smoked and n=50 non-smoked cheese samples. The lactic acid bacteria (LAB) were cultured on MRS, APT and MSE agars at 30 °C, coliform bacteria on VRBL agar at 37 °C, total count of bacteria (TCB) on Plate count agar at 30 °C and enterococci on Enterococcus selective agar at 37 °C. Gram-positive and gram-negative strains were subjected to identification by MALDI-TOF MS profiling. MALDI-TOF MS identification revealed four genera belonging to LAB including Lactococcus, Lactobacillus, Enterococcus and Leuconostoc. Lactobacillus was the most represented genus with seven species: Lactobacillus curvatus (L. curvatus), L. delbrueckii, L. fermentum, L. casei, L. paraplantarum, L. plantarum and L. sakei.. Escherichia coli, Enterobacter asburiae, Klebsiella oxytoca and K. pneumoniae were the most identified bacteria species from Enterobacteriales order.

Laboratory automation impact on antimicrobial resistance

Antibiotic resistance in common bacterial pathogens, such as Staphylococcus aureus, Escherichia coli, and Klebsiella pneumoniae, has significantly limited the therapeutic options available for management of infectious diseases. While the indiscriminant use of broad spectrum antibiotics is a significant contributing factor, a more fundamental problem exists. Diagnostic microbiology test results have historically been available too late to be useful. This is, in part, due to the nature of the test methods and in part due to workflow practices in the laboratory. Thus, patients remain on empiric treatments that are frequently ineffective or unnecessarily too broad spectrum1,2. Microscopy and bacterial cultures are mainstays in the microbiology lab, using techniques developed more than 100 years ago. Although microbiologists speak with pride about the ‘art' of their science, the clinical value of the diagnostic tests is frequently lost because of the delays in reporting results with these ‘traditional' approaches. Fortunately, the practice of clinical microbiology is undergoing a dramatic transformation with the introduction of molecular diagnostics, primarily for rapid diagnosis of infections caused by viruses and difficult to grow bacteria, MALDI-TOF mass spectrometry for identification of bacteria, mycobacteria and fungi, and automation of all practices in bacteriology.

Identification by mass spectrometry and automated susceptibility testing from positive bottles: a simple, rapid, and standardized approach to reduce the turnaround time in the management of blood cultures

BackgroundSpeeding up identification and antimicrobial susceptibility testing (AST) is of foremost importance in the management of blood cultures. Here, we describe a simple, rapid, and standardized approach based on a very short-term incubation on solid medium from positive blood cultures followed by MALDI-TOF mass spectrometry identification and automated AST. The aim of the study was to evaluate the impact in the laboratory practice of this new procedure with respect to that previously used (standard method) by comparing TAT and cumulative percentage of final reports to clinicians.ResultsCompared with the standard method, the new procedure gave correct organism identification at genus or species level in 98.4% of monomicrobial samples. AST resulted in 97.7% essential agreement and 98.1% categorical agreement, with 0.9% minor errors, 1.0% major error, and 1.5% very major errors. The mean turnaround time to identification and AST was 61.4 h by using the new method compared to 83.1 h by using standard procedure. Concerning cumulative percentages of final reports, approximately a third of results were available at 48 h from the check-in of the sample when using the new procedure, whereas no final reports were ready at the same time with the standard method.ConclusionsThe new procedure allows faster and reliable results using a simple and standardized approach. Thus, it represents an important tool for a more rapid management of blood cultures when molecular methods are not available in the laboratory.

Comparison of direct smear and chemical extraction methods for MALDI-TOF mass spectrometry identification of clinical relevant anaerobic bacteria

BackgroundThe Bruker Biotyper MALDI-TOF MS (Biotyper) system was evaluated for identification of anaerobic bacteria by chemical extraction and the direct smear technique. MethodA total of 216 strains of anaerobic bacteria representing 36 species were analyzed by two methods. 16S rDNA sequence analysis was used to resolve discrepancies. ResultsThe results showed that 202/216 (93.5%) strains were correctly identified following chemical extraction, among them, 176 strains (81.5%) were secured to both genus and species (score>2.00); another 26 strains (12%) were secured to genus only (score between 1.70 and 2.00). Following direct smear, 194/216 (89.8%) anaerobic bacteria were identified, 155 strains (71.7%) were secured to both genus and species (score)>2.0 whereas 39 (18%) strains were identified to genus only (score between 1.70 and 2.00). Fourteen strains were not identified (score<1.70) by MALDI-TOF MS following chemical extraction whereas 22 strains were not identified with the direct smear technique. Although direct smear had a less isolate number for score values>2.00, However the overall identification differences were not statistically significant (0.05<P<0.1). ConclusionMALDI-TOF MS identification following the direct smear technique appears to be non-inferior to standard chemical extraction. It may be an acceptable alternative to chemical extraction methods for routine identification of anaerobic bacteria in a medical microbiology laboratory.

MALDI-TOF mass spectrometry for the identification of lactic acid bacteria isolated from a French cheese: The Maroilles

In this study we identified the culturable population of mesophilic lactic acid bacteria (LAB) from a French cheese Maroilles made either with raw or pasteurized milk using MALDI-TOF mass spectrometry (MS). Samples from rind and heart of Maroilles cheese were used, the LAB were selected on MRS agar at 30°C and 197 Gram-positive and catalase-negative strains were subjected to identification by MALDI-TOF MS profiling. All strains were unambiguously identified: 105 strains from Maroilles made with raw milk (38 on the rind and 67 in the heart) and 92 strains from Maroilles made with pasteurized milk (39 on the rind and 53 in the heart). MALDI-TOF MS identification allowed identification of three genera belonging to LAB including Lactobacillus, Enterococcus and Leuconostoc. Lactobacillus was the most represented genus with seven species: Lactobacillus plantarum (L. plantarum), L. paracasei, L. curvatus, L. rhamnosus, L. fructivorans, L. parabuchneri, L. brevis found in Maroilles made with both kind of milk. The correlation between the 16S rDNA-based identification performed on selected strains and those obtained by MALDI-TOF-MS demonstrates that this fast, economically affordable, robust and reliable method for bacteria characterisation stands as an attractive alternative to the commonly-used methods and its application in food industry is discussed.

The impact of protein extraction protocols on the performance of currently available MALDI-TOF mass spectrometry for identification of mycobacterial clinical isolates cultured in liquid media

BackgroundProtein extraction step is particularly important for identification of mycobacterial isolates by MALDI-TOF mass spectrometry (MS) because of its thick and solid cell wall. This study compared the performance of MALDI-TOF MS for identification of mycobacterial clinical isolates cultured in liquid media between heating-based protocol and non-heating protocol. MethodsClinical mycobacterial isolates cultured in liquid media were prospectively analyzed. Reference identification was real-time PCR and restriction fragment length polymorphism. The specimens prepared by heating protocol and non-heating protocol were tested using MALDI Biotyper (Bruker Daltonics, Bremen, Germany) and Vitek MS (bioMérieux, Marcy l'Etoile, France), respectively. ResultsAmong the 206 clinical specimens prepared by heating method, identification rates were 90.3% and 60.7% in MALDI Biotyper and Vitek MS, respectively. Identification accuracy of MALDI Biotyper and Vitek MS was 100% for the isolates of Mycobacterium tuberculosis complex (MTBC), Mycobacterium avium, Mycobacterium intracellulare, Mycobacterium abscessus and Mycobacterium fortuitum. Among the 121 clinical specimens prepared by non-heating method, identification rate for MALDI Biotyper and Vitek MS were 61.2% and 69.4%, respectively. Identification accuracy of MALDI Biotyper/Vitek MS were 92.9%/94.1% for MTBC, 92.9%/100% for M. avium, 90%/100% for M. intracellulare, 100%/100% for M. abscessus and 100%/100% for M. fortuitum. ConclusionsThe performance of MALDI-TOF MS for identification of mycobacterial clinical isolates is affected by protein extraction protocol. For best performance, protein extraction protocol should be chosen considering the MALDI-TOF MS system. In the present study, heating protocol with MALDI Biotyper system showed reliable identification results for mycobacterial clinical isolates.

89 Potential impact using MALDI-TOF mass spectrometry for identification on the epidemiology of non-fermenting Gram-negative bacilli isolated from cystic fibrosis patients

89 Potential impact using MALDI-TOF mass spectrometry for identification on the epidemiology of non-fermenting Gram-negative bacilli isolated from cystic fibrosis patients

Routine identification and mixed species detection in 6,192 clinical yeast isolates.

The clinical laboratory methods used to diagnose yeast infections should be rapid, reliable, and capable of detecting mixed infections with species exhibiting a distinct antifungal susceptibility profile. In this study, we report the performance of a procedure combining the detection of mixed yeast cultures with a chromogenic medium and MALDI-TOF identification of the colonies. We then evaluated the impact that (i) the isolation medium and (ii) lowering the identification log score (LS) threshold value have on yeast identification performance in the routine laboratory.Among 15,661 clinical samples analyzed, 5,671 tested positive and 6,192 yeasts of 42 distinct species were identified. Overall, 6,117 isolates (98.79%) were identified on the first or second MALDI-TOF Mass Spectrometry (MS) attempt, yielding an average yeast species identification turnaround time of 0.346 days (95% CI [0.326 to 0.364]). The 75 remaining isolates were identified via nucleotide sequencing. Mixed infections accounted for 498 (8.78%) of the positive samples. The MALDI-TOF MS identification procedure performed well, regardless of the culture media tested. Lowering the recommended 2.0 LS threshold value to 1.8 would reduce the number of required (i) second MALDI-TOF MS identification attempts (178 vs. 490) and (ii) ITS2 and D1-D2 sequence-based identifications (17 vs. 75), while achieving an adequate identification rate (6,183/6,192, 99.85%).In conclusion, we propose applying a 1.8 LS threshold combined with chromogenic medium subculture to optimize the yeast identification workflow and detect mixed infection in the clinical laboratory.

Assessment of Reproducibility of Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry for Bacterial and Yeast Identification.

Matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry (MS) has revolutionized the identification of clinical bacterial and yeast isolates. However, data describing the reproducibility of MALDI-TOF MS for microbial identification are scarce. In this study, we show that MALDI-TOF MS-based microbial identification is highly reproducible and can tolerate numerous variables, including differences in testing environments, instruments, operators, reagent lots, and sample positioning patterns. Finally, we reveal that samples of bacterial and yeast isolates prepared for MALDI-TOF MS identification can be repeatedly analyzed without compromising organism identification.

Performance of mass spectrometric identification of bacteria and yeasts routinely isolated in a clinical microbiology laboratory using MALDI-TOF MS.

Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) is an emerging technology newly applied to identifying bacterial and yeast strains. The aim of this study was to evaluate the clinical performance of the VITEK(®) MS system in the identification of bacteria and yeast strains routinely isolated from clinical samples. We prospectively analyzed routine MALDI-TOF mass spectrometry identification in parallel with conventional phenotypic identification of bacteria and yeasts regardless of phylum or source of isolation. Discordant results were resolved with 16S rDNA or internal transcribed spacer (ITS) gene sequencing. Colonies (a single deposit on a MALDI disposable target without any prior extraction step) were analyzed using the VITEK(®) MS system. Peptide spectra acquired by the system were compared with the VITEK(®) MS IVD database Version 2.0, and the identification scores were recorded. Of the 1,181 isolates (1,061 bacterial isolates and 120 yeast isolates) analyzed, 99.5% were correctly identified by MALDI-TOF mass spectrometry; 95.7% identified to the species level, 3.6% identified to the genus level, and 0.3% identified within a range of species belonging to different genera. Conversely, 0.1% of isolates were misidentified and 0.4% were unidentified, partly because the species were not included in the database. Re-testing using a second deposit provided a successful identification for 0.5% of isolates unidentified with the first deposit. Our results show that the VITEK(®) MS system has exceptional performance in identifying bacteria and yeast by comparing acquired peptide spectra to those contained in its database. MALDI-TOF mass spectrometry is a rapid, accurate, and relatively inexpensive method for bacterial and yeast identification. Our results demonstrate that the VITEK(®) MS system is a fast and reliable technique, and has the potential to replace conventional phenotypic identification for most bacterial and yeast strains routinely isolated in clinical microbiology laboratories.