Speciation of coagulase negative staphylococci, isolated from indoor air, using SDS page gel bands of expressed proteins followed by MALDI TOF MS and MALDI TOF-TOF MS-MS analysis of tryptic peptides

Application of MALDI-TOF MS for identification of environmental bacteria: A review

Bacteria play a variety of roles in the environment. They maintain the balance in the ecosystem and provide different ecosystem services such as in biogeochemical cycling of nutrients, biodegradation of toxic pollutants, and others. Therefore, isolation and identification of different environmental bacteria are important to most environmental research. Due to the high cost and time associated with the conventional molecular techniques, matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) has gained considerable attention for routine identification of bacteria. This review aims to provide an overview of the application of MALDI-TOF MS in various environmental studies through bibliometric analysis and literature review. The bibliometric analysis helped to understand the time-variable application of MALDI-TOF MS in various environmental studies. The categorical literature review covers various environmental studies comprising areas like ecology, food microbiology, environmental biotechnology, agriculture, and plant sciences, which show the application of the technique for identification and characterization of pollutant-degrading, plant-associated, disease-causing, soil-beneficial, and other environmental bacteria. Further research should focus on bridging the gap between the phylogenetic identity of bacteria and their specific environmental functions or metabolic traits that can help in rapid advancements in environmental research, thereby, improving time and cost savings.

Strategy for the enrichment of protein biomarkers from diverse bacterial select agents

BACKGROUND

Some pathogenic bacteria can be potentially used for nefarious applications in the event of bioterrorism or biowarfare. Accurate identification of biological agent from clinical and diverse environmental matrices is of paramount importance for implementation of medical countermeasures and biothreat mitigation.

OBJECTIVE

A novel methodology is reported here for the development of a novel enrichment strategy for the generally conserved abundant bacterial proteins for an accurate downstream species identification using tandem MS analysis in biothreat scenario.

METHODS

Conserved regions in the common bacterial protein markers were analyzed using bioinformatic tools and stitched for a possible generic immuno-capture for an intended downstream MS/MS analysis. Phylogenetic analysis of selected proteins was carried out and synthetic constructs were generated for the expression of conserved stitched regions of 60 kDa chaperonin GroEL. Hyper-immune serum was raised against recombinant synthetic GroEL protein.

RESULTS

The conserved regions of common bacterial proteins were stitched for a possible generic immuno-capture and subsequent specific identification by tandem MS using variable regions of the molecule. Phylogenetic analysis of selected proteins was carried out and synthetic constructs were generated for the expression of conserved stitched regions of GroEL. In a proof-of-concept study, hyper-immune serum raised against recombinant synthetic GroEL protein exhibited reactivity with ~60 KDa proteins from the cell lysates of three bacterial species tested.

CONCLUSION

The envisaged methodology can lead to the development of a novel enrichment strategy for the abundant bacterial proteins from complex environmental matrices for the downstream species identification with increased sensitivity and substantially reduce the time-to-result.

Protein biomarker elucidation for the verification of biological agents in the taxonomic group of Gammaproteobacteria using tandem mass spectrometry

Some pathogenic microbes can be used for nefarious applications and instigate population-based fear. In a bio-threat scenario, rapid and accurate methods to detect biological agents in a wide range of complex environmental and clinical matrices, is of paramount importance for the implementation of mitigation protocols and medical countermeasures. This study describes targeted and shot-gun tandem MS based approaches for the verification of biological agents from the environmental samples. The marker proteins and peptides were elucidated by an exhaustive literature mining, in silico analysis of prioritized proteins, and MS/MS analysis of abundant proteins from selected bacterial species. For the shot-gun methodology, tandem MS analysis of abundant peptides was carried from spiked samples. The validation experiments employing a combination of shot-gun tandem MS analysis and a targeted search reported here is a proof of concept to show the applicability of the methodology for the unambiguous verification of biological agents at sub-species level, even with limited fractionation of crude protein extracts from environmental samples.

Staphylococcus lugdunensis Septic Arthritis following Arthroscopic Anterior Cruciate Ligament Reconstruction

Summary. We report two cases of Staphylococcus lugdunensis (S. lugdunensis) septic arthritis following arthroscopic anterior cruciate ligament (ACL) reconstruction. Both initial surgical procedures were ACL reconstruction along with simultaneous collateral ligament and meniscus procedures. Patients presented with septic arthritis three and ten weeks following the index procedure. Both patients successfully recovered with early arthroscopic irrigation, debridement, and synovial culture, in addition to long-term parenteral and oral antibiotics.Staphylococcus lugdunensis (S. lugdunensis) septic arthritis following arthroscopic anterior cruciate ligament (ACL) reconstruction. Both initial surgical procedures were ACL reconstruction along with simultaneous collateral ligament and meniscus procedures. Patients presented with septic arthritis three and ten weeks following the index procedure. Both patients successfully recovered with early arthroscopic irrigation, debridement, and synovial culture, in addition to long-term parenteral and oral antibiotics.S. lugdunensis) septic arthritis following arthroscopic anterior cruciate ligament (ACL) reconstruction. Both initial surgical procedures were ACL reconstruction along with simultaneous collateral ligament and meniscus procedures. Patients presented with septic arthritis three and ten weeks following the index procedure. Both patients successfully recovered with early arthroscopic irrigation, debridement, and synovial culture, in addition to long-term parenteral and oral antibiotics.

Elucidation of protein biomarkers for verification of selected biological warfare agents using tandem mass spectrometry

Some pathogens and toxins have the potential to be used as weapons of mass destruction and instigate population-based fear. Efforts to mitigate biothreat require development of efficient countermeasures which in turn relies on fast and accurate methods to detect the biological agents in a range of complex matrices including environmental and clinical samples. We report here an mass spectrometry (MS) based methodology, employing both targeted and shot-gun approaches for the verification of biological agents from the environmental samples. Our shot-gun methodology relied on tandem MS analysis of abundant peptides from the spiked samples, whereas, the targeted method was based on an extensive elucidation of marker proteins and unique peptides resulting in the generation of an inclusion list of masses reflecting relevant peptides for the unambiguous identification of nine bacterial species [listed as priority agents of bioterrorism by Centre for Disease Control and Prevention (CDC)] belonging to phylogenetically diverse genera. The marker peptides were elucidated by extensive literature mining, in silico analysis, and tandem MS (MS/MS) analysis of abundant proteins of the cultivated bacterial species in our laboratory. A combination of shot-gun MS/MS analysis and the targeted search using a panel of unique peptides is likely to provide unambiguous verification of biological agents at sub-species level, even with limited fractionation of crude protein extracts from environmental samples. The comprehensive list of peptides reflected in the inclusion list, makes a valuable resource for the multiplex analysis of select biothreat agents and further development of targeted MS/MS assays.

Antimicrobial resistance patterns and biofilm formation of coagulase-negative Staphylococcus species isolated from subclinical mastitis cow milk samples submitted to the Onderstepoort Milk Laboratory

Background

Increased prevalence of antimicrobial resistance, treatment failure, and financial losses have been reported in dairy cows with coagulase-negative Staphylococcus (CoNS) clinical mastitis, however, studies on CoNS infections are limited in South Africa. Therefore, the objectives of this study were to investigate the antimicrobial resistance patterns and biofilm formation in CoNS isolated from cow milk samples submitted to the Onderstepoort Milk Laboratory.

Results

A total of 142 confirmed CoNS isolates were used for this study. Biofilm formation was identified in 18% of CoNS tested. Staphylococcus chromogenes (11%) had the highest proportion of biofilm formation followed by S. haemolyticus (4.0%), S. epidermidis, S. hominis, S. xylosus, and S. simulans with 1% respectively. Ninety percent (90%) of CoNS were resistant to at least one antimicrobial (AMR) and 51% were multidrug-resistant (MDR). Resistance among CoNS was the highest to ampicillin (90%) and penicillin (89%), few isolates resistant to cefoxitin and vancomycin, 9% respectively. Similarly, MDR-S. haemolyticus (44%), MDR-S. epidermidis (65%), and MDR-S. chromogenes (52%) were mainly resistant to penicillins. The most common resistance patterns observed were resistance to penicillin-ampicillin (16%) and penicillin-ampicillin-erythromycin (10%). Only 42% of biofilm positive CoNS were MDR.

Conclusion

The majority of CoNS in this study were resistance to penicillins. In addition, most isolates were β-lactam resistant and MDR. Biofilm formation among the CoNS in this study was uncommon and there was no significant difference in the proportion of MDR-CoNS based on the ability to form a biofilm.

Effect of bio-engineering on size, shape, composition and rigidity of bacterial microcompartments

Bacterial microcompartments (BMCs) are proteinaceous organelles that are found in a broad range of bacteria and are composed of an outer shell that encases an enzyme cargo representing a specific metabolic process. The outer shell is made from a number of different proteins that form hexameric and pentameric tiles, which interact to allow the formation of a polyhedral edifice. We have previously shown that the Citrobacter freundii BMC associated with 1,2-propanediol utilization can be transferred into Escherichia coli to generate a recombinant BMC and that empty BMCs can be formed from just the shell proteins alone. Herein, a detailed structural and proteomic characterization of the wild type BMC is compared to the recombinant BMC and a number of empty BMC variants by 2D-gel electrophoresis, mass spectrometry, transmission electron microscopy (TEM) and atomic force microscopy (AFM). Specifically, it is shown that the wild type BMC and the recombinant BMC are similar in terms of composition, size, shape and mechanical properties, whereas the empty BMC variants are shown to be smaller, hollow and less malleable.

Mass spectrometry for the detection of bioterrorism agents: from environmental to clinical applications

In the current context of international conflicts and localized terrorist actions, there is unfortunately a permanent threat of attacks with unconventional warfare agents. Among these, biological agents such as toxins, microorganisms, and viruses deserve particular attention owing to their ease of production and dissemination. Mass spectrometry (MS)-based techniques for the detection and quantification of biological agents have a decisive role to play for countermeasures in a scenario of biological attacks. The application of MS to every field of both organic and macromolecular species has in recent years been revolutionized by the development of soft ionization techniques (MALDI and ESI), and by the continuous development of MS technologies (high resolution, accurate mass HR/AM instruments, novel analyzers, hybrid configurations). New possibilities have emerged for exquisite specific and sensitive detection of biological warfare agents. MS-based strategies for clinical application can now address a wide range of analytical questions mainly including issues related to the complexity of biological samples and their available volume. Multiplexed toxin detection, discovery of new markers through omics approaches, and identification of untargeted microbiological or of novel molecular targets are examples of applications. In this paper, we will present these technological advances along with the novel perspectives offered by omics approaches to clinical detection and follow-up.

Species determination within Staphylococcus genus by extended PCR-restriction fragment length polymorphism of saoC gene

Genetic methods based on PCR-restriction fragment length polymorphism (RFLP) are widely used for microbial species determination. In this study, we present the application of saoC gene as an effective tool for species determination and within-species diversity analysis for Staphylococcus genus. The unique sequence diversity of saoC allows us to apply four restriction enzymes to obtain RFLP patterns, which appear highly distinctive even among closely related species as well as atypical isolates of environmental origin. Such patterns were successfully obtained for 26 species belonging to Staphylococcus genus. What is more, tracing polymorphisms detected by different restriction enzymes allowed for basic phylogeny analysis for Staphylococcus aureus, which is potentially applicable for other staphylococcal species.

Reprint of "Assessment of marker proteins identified in whole cell extracts for bacterial speciation using liquid chromatography electrospray ionization tandem mass spectrometry"

Staphylococcal strains (CoNS) were speciated in this study. Digests of proteins released from whole cells were converted to tryptic peptides for analysis. Liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESI MS/MS, Orbitrap) was employed for peptide analysis. Data analysis was performed employing the open-source software X!Tandem which uses sequenced genomes to generate a virtual peptide database for comparison to experimental data. The search database was modified to include the genomes of the 11 Staphylococcus species most commonly isolated from man. The number of total peptides matching each protein along with the number of peptides specifically matching to the homologue (or homologues) for strains of the same species were assessed. Any peptides not matching to the species examined were considered conflict peptides. The proteins typically identified with the largest percentage of sequence coverage, number of matched peptides and number of peptides corresponding to only the correct species were elongation factor Tu (EF Tu) and enolase (Enol). Additional proteins with consistently observed peptides as well as peptides matching only homologues from the same species were citrate synthase (CS) and 1-pyrroline-5-carboxylate dehydrogenase (1P5CD). Protein markers, previously identified from gel slices, (aconitate hydratase and oxoglutarate dehydrogenase) were found to provide low confidence scores when employing whole cell digests. The methodological approach described here provides a simple yet elegant way of identification of staphylococci. However, perhaps more importantly the technology should be applicable universally for identification of any bacterial species.

Reprint of "Identification of staphylococcal species based on variations in protein sequences (mass spectrometry) and DNA sequence (sodA microarray)"

This report is among the first using sequence variation in newly discovered protein markers for staphylococcal (or indeed any other bacterial) speciation. Variation, at the DNA sequence level, in the sodA gene (commonly used for staphylococcal speciation) provided excellent correlation. Relatedness among strains was also assessed using protein profiling using microcapillary electrophoresis and pulsed field electrophoresis. A total of 64 strains were analyzed including reference strains representing the 11 staphylococcal species most commonly isolated from man (Staphylococcus aureus and 10 coagulase negative species [CoNS]). Matrix assisted time of flight ionization/ionization mass spectrometry (MALDI TOF MS) and liquid chromatography-electrospray ionization tandem mass spectrometry (LC ESI MS/MS) were used for peptide analysis of proteins isolated from gel bands. Comparison of experimental spectra of unknowns versus spectra of peptides derived from reference strains allowed bacterial identification after MALDI TOF MS analysis. After LC-MS/MS analysis of gel bands bacterial speciation was performed by comparing experimental spectra versus virtual spectra using the software X!Tandem. Finally LC-MS/MS was performed on whole proteomes and data analysis also employing X!tandem. Aconitate hydratase and oxoglutarate dehydrogenase served as marker proteins on focused analysis after gel separation. Alternatively on full proteomics analysis elongation factor Tu generally provided the highest confidence in staphylococcal speciation.

Identification of staphylococcal species based on variations in protein sequences (mass spectrometry) and DNA sequence (sodA microarray)

This report is among the first using sequence variation in newly discovered protein markers for staphylococcal (or indeed any other bacterial) speciation. Variation, at the DNA sequence level, in the sodA gene (commonly used for staphylococcal speciation) provided excellent correlation. Relatedness among strains was also assessed using protein profiling using microcapillary electrophoresis and pulsed field electrophoresis. A total of 64 strains were analyzed including reference strains representing the 11 staphylococcal species most commonly isolated from man (Staphylococcus aureus and 10 coagulase negative species [CoNS]). Matrix assisted time of flight ionization/ionization mass spectrometry (MALDI TOF MS) and liquid chromatography-electrospray ionization tandem mass spectrometry (LC ESI MS/MS) were used for peptide analysis of proteins isolated from gel bands. Comparison of experimental spectra of unknowns versus spectra of peptides derived from reference strains allowed bacterial identification after MALDI TOF MS analysis. After LC-MS/MS analysis of gel bands bacterial speciation was performed by comparing experimental spectra versus virtual spectra using the software X!Tandem. Finally LC-MS/MS was performed on whole proteomes and data analysis also employing X!tandem. Aconitate hydratase and oxoglutarate dehydrogenase served as marker proteins on focused analysis after gel separation. Alternatively on full proteomics analysis elongation factor Tu generally provided the highest confidence in staphylococcal speciation.

Assessment of marker proteins identified in whole cell extracts for bacterial speciation using liquid chromatography electrospray ionization tandem mass spectrometry

Staphylococcal strains (CoNS) were speciated in this study. Digests of proteins released from whole cells were converted to tryptic peptides for analysis. Liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESI MS/MS, Orbitrap) was employed for peptide analysis. Data analysis was performed employing the open-source software X!Tandem which uses sequenced genomes to generate a virtual peptide database for comparison to experimental data. The search database was modified to include the genomes of the 11 Staphylococcus species most commonly isolated from man. The number of total peptides matching each protein along with the number of peptides specifically matching to the homologue (or homologues) for strains of the same species were assessed. Any peptides not matching to the species examined were considered conflict peptides. The proteins typically identified with the largest percentage of sequence coverage, number of matched peptides and number of peptides corresponding to only the correct species were elongation factor Tu (EF Tu) and enolase (Enol). Additional proteins with consistently observed peptides as well as peptides matching only homologues from the same species were citrate synthase (CS) and 1-pyrroline-5-carboxylate dehydrogenase (1P5CD). Protein markers, previously identified from gel slices, (aconitate hydratase and oxoglutarate dehydrogenase) were found to provide low confidence scores when employing whole cell digests. The methodological approach described here provides a simple yet elegant way of identification of staphylococci. However, perhaps more importantly the technology should be applicable universally for identification of any bacterial species.

MALDI TOF MS profiling of bacteria at the strain level: a review

Since the advent of the use of matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometry (TOF MS) as a tool for microbial characterization, efforts to increase the taxonomic resolution of the approach have been made. The rapidity and efficacy of the approach have suggested applications in counter-bioterrorism, prevention of food contamination, and monitoring the spread of antibiotic-resistant bacteria. Strain-level resolution has been reported with diverse bacteria, using library-based and bioinformatics-enabled approaches. Three types of characterization at the strain level have been reported: strain categorization, strain differentiation, and strain identification. Efforts to enhance the library-based approach have involved sample pre-treatment and data reduction strategies. Bioinformatics approaches have leveraged the ever-increasing amount of publicly available genomic and proteomic data to attain strain-level characterization. Bioinformatics-enabled strategies have facilitated strain characterization via intact biomarker identification, bottom-up, and top-down approaches. Rigorous quantitative and advanced statistical analyses have fostered success at the strain level with both approaches. Library-based approaches can be limited by effects of sample preparation and culture conditions on reproducibility, whereas bioinformatics-enabled approaches are typically limited to bacteria, for which genetic and/or proteomic data are available. Biological molecules other than proteins produced in strain-specific manners, including lipids and lipopeptides, might represent other avenues by which strain-level resolution might be attained. Immunological and lectin-based chemistries have shown promise to enhance sensitivity and specificity. Whereas the limits of the taxonomic resolution of MALDI TOF MS profiling of bacteria appears bacterium-specific, recent data suggest that these limits might not yet have been reached.

Comparison of the accuracy of matrix-assisted laser desorption ionization-time of flight mass spectrometry with that of other commercial identification systems for identifying Staphylococcus saprophyticus in urine

Among 30 urinary isolates of Staphylococcus saprophyticus identified by sequencing methods, the rate of accurate identification was 100% for Bruker Biotyper matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS), 86.7% for the Phoenix PID and Vitek 2 GP systems, 93.3% for the MicroScan GP33 system, and 46.7% for the BBL CHROMagar Orientation system.

Could public restrooms be an environment for bacterial resistomes?

Antibiotic resistance in bacteria remains a major problem and environments that help to maintain such resistance, represent a significant problem to infection control in the community. Restrooms have always been regarded as potential sources of infectious diseases and we suggest they have the potential to sustain bacterial "resistomes". Recent studies have demonstrated the wide range of different bacterial phyla that can be found in non-healthcare restrooms. In our study we focused on the Staphylococci. These species are often skin contaminants on man and have been reported as common restroom isolates in recent molecular studies. We collected samples from 18 toilets sited in 4 different public buildings. Using MALDI-TOF-MS and other techniques, we identified a wide range of antibiotic resistant Staphylococci and other bacteria from our samples. We identified 19 different Staphylococcal species within our isolates and 37.8% of the isolates were drug resistant. We also identified different Staphylococcal species with the same antibiograms inhabiting the same restrooms. Bacterial "resistomes" are communities of bacteria often localised in specific areas and within these environments drug resistance determinants may be freely transferred. Our study shows that non-healthcare restrooms are a source of antibiotic resistant bacteria where a collection of antibiotic resistance genes in pathogenic and non-pathogenic bacteria could form a resistome containing a "nexus of genetic diversity"

Identification of Staphylococcus saprophyticus isolated from patients with urinary tract infection using a simple set of biochemical tests correlating with 16S-23S interspace region molecular weight patterns

The emergence of Staphylococcus spp. not only as human pathogens, but also as reservoirs of antibiotic resistance determinants, requires the development of methods for their rapid and reliable identification in medically important samples. The aim of this study was to compare three phenotypic methods for the identification of Staphylococcus spp. isolated from patients with urinary tract infection using the PCR of the 16S-23S interspace region generating molecular weight patterns (ITR-PCR) as reference. All 57 S. saprophyticus studied were correctly identified using only the novobiocin disk. A rate of agreement of 98.0% was obtained for the simplified battery of biochemical tests in relation to ITR-PCR, whereas the Vitek I system and novobiocin disk showed 81.2% and 89.1% agreement, respectively. No other novobiocin-resistant non-S. saprophyticus strain was identified. Thus, the novobiocin disk is a feasible alternative for the identification of S. saprophyticus in urine samples in laboratories with limited resources. ITR-PCR and the simplified battery of biochemical tests were more reliable than the commercial systems currently available. This study confirms that automated systems are still unable to correctly differentiate CoNS species and that simple, reliable and inexpensive methods can be used for routine identification.

The use of whole-cell protein profile analysis by SDS-PAGE as an accurate tool to identify species and subspecies of coagulase-negative staphylococci

We used sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) as a tool to characterize coagulase-negative staphylococci (CoNS). Of 253 clinical isolates and 10 control strains, five species and four subspecies were analyzed. All the isolates were identified using conventional phenotypic tests and SDS-PAGE. Discrepant results between these methods, as well as less common species and subspecies, were confirmed by sodA and 16S rDNA gene sequencing. Intraspecies similarities, calculated by the Dice coefficient, were significantly higher when compared to interspecies similarities. The conventional method failed to identify eight (3.2%) molecularly defined and SDS-PAGE-determined isolates. Therefore, SDS-PAGE was able to discriminate between all unidentified or misidentified isolates using a phenotypic method. In addition, SDS-PAGE identified all atypical isolates using biochemistry and CoNS at the subspecies level.

Characterization of Micrococcus strains isolated from indoor air

The characterization of microbes, such as opportunists and pathogens (e.g., methicillin resistant Staphylococcus aureus [MRSA]), in indoor air is important for understanding disease transmission from person-to-person. Common genera found in the human skin microbiome include Micrococcus and Staphylococcus, but there only a limited number of tests to differentiate these genera and/or species. Both genera are believed to be released into indoor air from the shedding of human skin and are morphologically difficult to distinguish. In the current work, after the extraction of proteins from micrococci and the separation of these proteins on one dimensional electrophoretic gels, tryptic peptides were analyzed by MALDI TOF MS and the mass profiles compared with those of a reference strain (ATCC 4698). The results confirmed that all strains were consistent in identity with Micrococcus luteus.

Biochemical markers and protein pattern analysis for canine coagulase-positive staphylococci and their distribution on dog skin

Coagulase-positive staphylococci (CoPS) including S. pseudintermedius, S. schleiferi subsp. coagulans and S. aureus are etiological agents of dermatitis in companion animals and can be zoonotic pathogens. To date no consensual biochemical marker for routine microbiological identification of these species has been identified. The aim of this study was to evaluate biochemical markers and compare the results with the approved molecular method, multiplex-PCR (M-PCR), and confirm their species-specific phenotypic characteristic by using SDS-PAGE. The distribution and frequency of CoPS species were also determined. Three hundred and thirty-seven canine CoPS isolates were obtained from the nasal mucosa, perineum and groins of 66 healthy dogs and were identified by the M-PCR as S. aureus (n=5), S. pseudintermedius (n=263) and S. schleiferi subsp. coagulans (n=69). Selected biochemical tests including the Voges-Proskauer test, mannitol broth fermentation, the assimilation of maltose, galactose, trahalose and lactose using broth medium, were successfully used to distinguish the three species of canine CoPS from other CoPS species. Additionally, species-specific protein patterns were also found to be useful for phenotypic differentiation, with good agreement with the results of M-PCR and the use of biochemical markers. S. aureus occured infrequently on dog skin while co-colonization with S. pseudintermedius and S. schleiferi subsp. coagulans was observed. We propose the use of consensual biochemical markers of canine CoPS with the presence of the unique protein patterns as an alternative tool for conventional laboratory use.

Identification of lethal Aspergillus at early growth stages based on matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Delayed and incorrect diagnoses are potential risk factors leading to high mortality of invasive aspergillosis (IA). Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry was used to acquire a wide mass spectral range and characterize the early process of asexual sporulation of lethal IA pathogens recovered on agar plates. Proteins were extracted using trifluoroacetic acid and soft ionized using an ultraviolet laser with the assistance of ferulic acid. At the second stage of sporulation with various differentiated structures, there are more specific peaks that can be used to discriminate different Aspergillus species than at the first stage, which features vegetative hyphae. Certain specific peaks are found in different strains of the same species, Aspergillus fumigatus. In addition, the relative standard deviations of the m/z ratios are much smaller than those of the relative intensities in these peaks. Therefore, common lethal Aspergillus species can be identified after short-term cultivation by matching species-specific m/z values.