MALDI-TOF MS Research Articles

Advancing photopolymerization and 3D printing: High-Performance NiII complexes bearing N2O2 Schiff-base ligands as photocatalysts

New high-performance photocatalysts based on metal structures are being developed for polymerization. However, using low-cost metals while ensuring effectiveness is challenging. In this study, two NiII complexes NiL1 and NiL2 were synthesized using N2O2 Schiff-base ligands bearing π-extended rings (naphthaldehyde (H2L1) and phenylsalicylaldehyde (H2L2) groups), respectively. These complexes were characterized by FTIR, UV–Vis and 1H NMR spectroscopy, elemental analysis, cyclic voltammetry, and MALDI-TOF mass spectrometry. NiL1 and NiL2 were evaluated in photoinitiating system as new photocatalysts for the Free Radical Photopolymerization of Ethoxylated (3) Trimethylolpropane Triacrylate (TMPETA) for violet and green light. Three-component systems were employed in the presence of Di-tert-butyl-diphenyl iodonium hexafluorophosphate (Iod) and ethyl dimethylaminobenzoate (EDB). The absorption, luminescence, and redox properties of nickel complexes and ligands were explored and compared for a better understanding of their structure/reactivity relationship. The designed nickel complexes showed good photoinitiation abilities. NiL2 exhibited the highest monomer conversion, and it was investigated in the on–off process under green light irradiation, demonstrating the efficiency of the system in reactivating the polymerization process. An oxidative pathway mechanism was proposed based on free energy, steady state photolysis and electron spin resonance spin trapping experiments. The best system was successfully applied in cationic photopolymerization and 3D printing.

The first synthesis and characterization of spiro and ansa-cyclotriphosphazenes with 3-Hydroxyflavone and induction of apoptosis in breast cancer (MCF-7)

In this study, the first series of 3-Hydroxyflavone substituted spiro, ansa-1,3-propanedioxy and 2,2-dimethyl 1,3-propanedioxy substituted cyclotriphosphazene compounds 9−12 were synthesized and their structures were characterized by MALDI-TOF MS, NMR (31P and 1H) and FT-IR spectroscopies. After the antioxidant (DPPH), total phenolic, and cytotoxicity (WST-8) activities of the compounds were determined, the mRNA expressions of multidrug resistance and apoptosis effects were investigated by RT-PCR analysis of the compounds in MCF-7 cells. While the DPPH activity of the compounds is 90.56%, the total phenolic activity is 187.01 mg. Cytotoxic activity IC50: 23.07 μM was detected in breast cell line. In addition, the cell death gene expression values of the compounds showed an increase in BAX, p53, Caspase-3 and Caspase-7 gene expressions, and a decrease in BCL-2. The compounds were determined to be notable for their effective cytotoxicity data in breast cancer (MCF-7) and indicators of apoptosis through BAX regulation.

Sulfatide imaging identifies tumor cells in colorectal cancer peritoneal metastases

Even with systemic chemotherapy, cytoreductive surgery (CRS), and hyperthermic intraperitoneal chemotherapy (HIPEC), peritoneal metastases (PM) remain a common site of disease progression for colorectal cancer (CRC) and are frequently associated with a poor prognosis. The mass spectrometry (MS) method known as Matrix-Assisted Laser Desorption/Ionization – Time of Flight (MALDI-TOF) is frequently used in medicine to identify structural compounds and biomarkers. It has been demonstrated that lipids are crucial in mediating the aggressive growth of tumors. In order to investigate the lipid profiles, particularly with regard to histological distribution, we used MALDI-TOF MS (MALDI-MS) and MALDI-TOF imaging MS (MALDI-IMS) on patient-derived tumor organoids (PDOs) and PM clinical samples. According to the MALDI-IMS research shown here, the predominant lipid signature of PDOs in PM tissues, glycosphingolipid (GSL) sulfates or sulfatides, or STs, is unique to the areas containing tumor cells and absent from the surrounding stromal compartments. Bioactive lipids are derived from arachidonic acid (AA), and AA-containing phosphatidylinositol (PI), or PI (18:0–20:4), is shown to be highly expressed in the stromal components. On the other hand, the tumor components contained a higher abundance of PI species with shorter and more saturated acyl chains (C34 and C36 carbons). The cellular subversion of PI and ST species may alter in ways that promote the growth, aggressiveness, and metastasis of tumor cells. Together, these findings suggest that the GSL/ST metabolic programming of PM may contain novel therapeutic targets to impede or halt PM progression.

Identification of Food Spoilage Fungi Using MALDI-TOF MS: Spectral Database Development and Application to Species Complex.

Fungi, including filamentous fungi and yeasts, are major contributors to global food losses and waste due to their ability to colonize a very large diversity of food raw materials and processed foods throughout the food chain. In addition, numerous fungal species are mycotoxin producers and can also be responsible for opportunistic infections. In recent years, MALDI-TOF MS has emerged as a valuable, rapid and reliable asset for fungal identification in order to ensure food safety and quality. In this context, this study aimed at expanding the VITEK® MS database with food-relevant fungal species and evaluate its performance, with a specific emphasis on species differentiation within species complexes. To this end, a total of 380 yeast and mold strains belonging to 51 genera and 133 species were added into the spectral database including species from five species complexes corresponding to Colletotrichum acutatum, Colletotrichum gloeosporioides, Fusarium dimerum, Mucor circinelloides complexes and Aspergillus series nigri. Database performances were evaluated by cross-validation and external validation using 78 fungal isolates with 96.55% and 90.48% correct identification, respectively. This study also showed the capacity of MALDI-TOF MS to differentiate closely related species within species complexes and further demonstrated the potential of this technique for the routine identification of fungi in an industrial context.

Investigation of different methods in rapid microbial identification directly from positive blood culture bottles by MALDI-TOF MS.

Sepsis is a life-threatening condition, and rapid and accurate identification of the causative microorganisms from blood cultures is crucial for timely and effective treatment. Although there are many studies on direct identification from blood cultures with MALDI-TOF MS, further standardization is still needed. In our study, we analyzed the performance of three different preparation methods and compared by using two analysis modules of the Bruker Biotyper MALDI-TOF MS for direct identification of bacteria from numerous positive blood culture bottles. The literature reports a limited number of studies that compare different preparation methods for direct blood culture identification, processing a large number of blood samples concurrently and evaluating the same samples as in our study. Moreover, although SDS is used very frequently in medical laboratories, there are few studies on direct identification from blood culture bottles. In our study, the highest correct identification rate was observed with the SDS method.

The polymicrobial nature of the oral cavity and claws of cats diagnosed by mass spectrometry and next-generation sequencing

Close contact between cats and humans increases the risk of transmission of zoonotic pathogens, through bites and scratches due to the complexity of microorganisms in the oral and nail microbiotas of felines. This study investigated the presence of bacteria and fungi in the oral cavity and claws of 100 apparently healthy cats using conventional and selective microbiological culture media, and next-generation sequencing (NGS) and mass spectrometry (MALDI-TOF MS). Furthermore, antimicrobial susceptibility testing of bacteria isolates was performed by disc diffusion method. In total, 671 bacteria and 33 yeasts were identified by MALDI-TOF MS. Neisseria animaloris (10.8 %), Staphylococcus felis (8.5 %), and Pasteurella multocida (7 %) were the most prevalent bacteria in oral cavity samples (n = 343), while the most common yeast (n = 19) was Candida albicans (68.4 %). Staphylococcus pettenkoferi (13.4 %), Staphylococcus felis (6.4 %), and Staphylococcus simulans (5.8 %) were the prevalent bacteria identified in the claw samples (n = 328), while Rhodotorula mucilaginosa (57.2 %) was the most common yeast (n = 14). NGS predominantly identified the genera Moraxella, Neisseria, Pasteurella, and Fusobacterium in oral cavity samples, whereas enterobacteria and staphylococci were prevalent in nail bed samples. In addition, the genera Capnocytophaga and Bartonella were identified, which have been described in serious human infections secondary to feline aggressions. Levofloxacin, marbofloxacin, and amoxicillin/clavulanic acid were the most effective drugs against the main groups of bacteria identified. Multidrug resistance was observed in 17 % of the bacterial isolates. Furthermore, three staphylococci harboring the methicillin resistance gene mecA were identified. We highlight the complexity of microorganisms inhabiting the oral/claw microbiotas of cats, the high resistance rate of the isolates to conventional antimicrobial agents, and the zoonotic risk of aggressions caused by bites and scratches from domestic cats.

Genotyping and Phenotyping of Indigenous Saccharomyces cerevisiae from a New Zealand Organic Winery and Commercial Sources Using Inter-Delta and MALDI-TOF MS Typing.

We used inter-delta typing (IDT) and MALDI-TOF profiling to characterize the genetic and phenotypic diversity of 45 commercially available winemaking Saccharomyces cerevisiae strains and 60 isolates from an organic winemaker from Waipara, New Zealand, as a stratified approach for predicting the commercial potential of indigenous isolates. A total of 35 IDTs were identified from the commercial strains, with another 17 novel types defined among the Waipara isolates. IDT 3 was a common type among strains associated with champagne production, and the only type in commercial strains also observed in indigenous isolates. MALDI-TOF MS also demonstrated its potential in S. cerevisiae typing, particularly when the high-mass region (m/z 2000-20,000) was used, with most indigenous strains from each of two fermentation systems distinguished. Furthermore, the comparison between commercial strains and indigenous isolates assigned to IDT 3 revealed a correlation between the low-mass data (m/z 500-4000) analysis and the recommended use of commercial winemaking strains. Both IDT and MALDI-TOF analyses offer useful insights into the genotypic and phenotypic diversity of S. cerevisiae, with MALDI-TOF offering potential advantages for the prediction of applications for novel, locally isolated strains that may be valuable for product development and diversification.

Clinical and mycological analysis of colonization by Candida spp. in oral leukoplakia and oral lichen planus.

This study aims to analyze the prevalence of Candida spp. colonization in oral leukoplakia and oral lichen planus lesions, verify the influence of systemic and local factors, besides identify and determine the in vitro antifungal susceptibility profile of Candida species. Samples were collected by swabbing from oral lesions and healthy mucosa and cultured on Sabouraud Dextrose and CHROMagar® Candida plates. Species identification was confirmed with MALDI-TOF MS analysis. Candida spp. was found in 36.8% of cases of oral leukoplakia and 18.2% of cases of oral lichen planus. Candida albicans was the only species found in oral lichen planus lesions (n = 2, 100%) and the most prevalent in oral leukoplakia (n = 5, 76.4%). Among the non-albicans Candida species found in oral leukoplakia were C. parapsilosis (n = 2, 25.5%) and C. tropicalis (n = 1, 14.1%). Candida isolates were susceptible to all antifungals tested. C. albicans was the most commonly found species in the studied lesions. No correlation was found between systemic and local factors with positive cases of oral lichen planus. However, smoking and alcohol consumption may be associated with positive cases of oral leukoplakia, especially the non-homogeneous clinical form. In addition, there is a possible predisposition to associated Candida colonization in cases of epithelial dysplasia found in oral leukoplakia. The antifungal medications tested showed excellent efficacy against isolates.

Periodontal and microbiological evaluation in cleft lip/palate patients undergoing orthodontic treatment: A cross‐sectional study

AbstractBackgroundThe present cross‐sectional study was undertaken to evaluate the periodontal and microbiological parameters in patients with surgically repaired unilateral cleft lip and palate (UCLP) undergoing orthodontic correction in comparison to patients without any cleft or orthodontic treatment.MethodsA total of 120 patients, out of initial 148 patients, between the age group 6 and 18 years were enrolled and divided into four groups with 30 patients each: non‐cleft patients without orthodontic treatment in Group 1, non‐cleft patients undergoing fixed orthodontic treatment in Group 2, patients with UCLP without any orthodontic treatment in Group 3, and patients with UCLP undergoing fixed orthodontic treatment in Group 4. Periodontal parameters including plaque index (PI), gingival index (GI), gingival bleeding index (GBI), community periodontal index of treatment needs (CPITN) index, pocket probing depth (PD), and tooth mobility were measured in all the groups. The subgingival plaque samples of all the patients were subjected to microbial evaluation using matrix‐assisted laser desorption ionization‐time of flight mass spectrometry (MALDI‐TOF‐MS) for clinical diagnosis.ResultsThe periodontal parameters were significantly raised in Group 4, followed by Group 3 and Group 2 in comparison to Group 1 (p < 0.01), thereby suggesting poor periodontal health in patients with UCLP undergoing orthodontic treatment. Statistically significant differences (p < 0.01) in counts of micro‐organisms among the groups were observed for P. gingivalis, P. intermedia, Veillonella, and Capnocytophaga, with the highest proportions in Group 4, indicating a deteriorating oral health in these patients.ConclusionPoor periodontal and microbial health in patients with UCLP undergoing orthodontic treatment indicates a need for reinforcement of oral hygiene practices among these patients.

Innovative strategies against superbugs: Developing an AI-CDSS for precise Stenotrophomonas maltophilia treatment

ObjectivesThe World Health Organization named Stenotrophomonas maltophilia (SM) a critical multi-drug resistant threat, necessitating rapid diagnostic strategies. Traditional culturing methods require up to 96 h, including 72 h for bacterial growth, identification with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) through protein profile analysis, and 24 h for antibiotic susceptibility testing. In this study, we aimed at developing an artificial intelligence-clinical decision support system (AI-CDSS) by integrating MALDI-TOF MS and machine learning to quickly identify levofloxacin and trimethoprim/sulfamethoxazole resistance in SM, optimizing treatment decisions. MethodsWe selected 8,662 SM from 165,299 MALDI-TOF MS-analysed bacterial specimens, collected from a major medical centre and four secondary hospitals. We exported mass-to-charge values and intensity spectral profiles from MALDI-TOF MS .mzML files to predict antibiotic susceptibility testing results, obtained with the VITEK-2 system using machine learning algorithms. We optimized the models with GridSearchCV and 5-fold cross-validation. ResultsWe identified distinct spectral differences between resistant and susceptible SM strains, demonstrating crucial resistance features. The machine learning models, including random forest, light-gradient boosting machine, and XGBoost, exhibited high accuracy. We established an AI-CDSS to offer healthcare professionals swift, data-driven advice on antibiotic use. ConclusionsMALDI-TOF MS and machine learning integration into an AI-CDSS significantly improved rapid SM resistance detection. This system reduced the identification time of resistant strains from 24 h to minutes after MALDI-TOF MS identification, providing timely and data-driven guidance. Combining MALDI-TOF MS with machine learning could enhance clinical decision-making and improve SM infection treatment outcomes.

Performance of 16S rRNA Gene Next-Generation Sequencing and the Culture Method in the Detection of Bacteria in Clinical Specimens.

Effective treatment of infectious diseases requires prompt and accurate bacterial identification and tailored antimicrobial treatments. Traditional culture methods are considered the gold standard, but their effectiveness diminishes for fastidious and hard-to-grow microorganisms. In recent years, molecular diagnostic tools such as 16S rRNA gene next-generation sequencing (16S NGS) have gained popularity in the field. We analysed data from samples submitted for 16S NGS between July 2022 and July 2023 at the Department of Advanced Translational Microbiology in Trieste, Italy. The study included samples submitted for both culture-based identification and 16S NGS. Conventional media were used for culture, and bacterial identification was performed using MALDI-TOF mass spectrometry. The V3 region of the 16S rRNA gene was sequenced using the Ion PGM platform. Among the 123 samples submitted, drainage fluids (38%) and blood (23%) were the most common, with requests predominantly from the Infectious Diseases (31.7%) and Orthopedic (21.13%) Units. In samples collected from patients with confirmed infections, 16S NGS demonstrated diagnostic utility in over 60% of cases, either by confirming culture results in 21% or providing enhanced detection in 40% of instances. Among the 71 patients who had received antibiotic therapies before sampling (mean 2.3 prior antibiotic days), pre-sampling antibiotic consumption did not significantly affect the sensitivity of 16S NGS. In routine microbiology laboratories, combining 16S NGS with culture method enhances the sensitivity of microbiological diagnostics, even when sampling is conducted during antibiotic therapy.

Prevalence and sensitivity of contagious and environmental cow mastitis-causing pathogens to antibiotics in Ukrainian farms

Mastitis is considered the most common and problematic disease, resulting in significant economic losses due to reduced milk yields, reduced quantity and quality of milk, treatment costs, and premature culling of animals. One of the traditional methods of treating mastitis in cows is using antibiotics, which leads to the emergence of polyresistant strains of microorganisms, the so-called Superbugs. The emergence of Superbugs, which are not sensitive to most existing antibiotics, is a major concern in veterinary and humane medicine. This study aimed to identify pathogens isolated from the secretion of the mammary gland of cows with mastitis to determine their spread and sensitivity to antibiotics. The samples of secretion from the udder were examined by bacteriological method. The isolates were identified by conventional methods and by the modern method – mass spectrometry (MALDI-TOF MS). The sensitivity of the bacterial isolates to antibiotics was determined by the disc diffusion method (Kirby-Bauer). The results of studies of cow mammary gland secretion samples indicate that 49.2% of the isolates are contagious, and 50.8% are environmental ones. The most common among the isolates of mastitis-causing pathogens were Streptoccocus аgalactiae – 16.9%, Streptococcus uberis – 10.9%, Staphylococcus aureus – 10.7%, E. Coli – 9.6%, Corynebacterium bovis – 7.3%, Staphylococcus haemolyticus – 4.8%, Staphylococcus chromogenes – 3.6%, Streptococcus dysgalactiae – 3.4%. Mastitis is caused by algae and yeast – 1% of all detected pathogens, respectively. According to the results of the determination of the sensitivity of isolates of mastitis-causing pathogens to antibiotics, it was found that most isolates were sensitive to Amoxicillin, Ceftiofur, and Rifampicin, and least of them – to Neomycin, Tylosin, Tilmicosin, Bacitracin.

An update on non-aureus staphylococci and mammaliicocci in cow milk: unveiling the presence of Staphylococcus borealis and Staphylococcus rostri by MALDI-TOF MS.

Non-aureus staphylococci and mammaliicocci (NASM) are the microorganisms most frequently isolated from milk. Given their numerosity and complexity, MALDI-TOF MS is one of the preferred species identification approaches. Nevertheless, reference mass spectra for the novel species Staphylococcus borealis were included only recently in the Bruker Biotyper System (MBT) library, and other species of veterinary interest such as S. rostri are still absent. This work provides an updated picture of the NASM species found in milk, gained by retrospectively analyzing the data relating to 21,864 milk samples, of which 6,278 from clinical mastitis (CM), 4,039 from subclinical mastitis (SCM), and 11,547 from herd survey (HS), with a spectrum library including both species. As a result, S. borealis was the second most frequently isolated NASM (17.07%) after S. chromogenes (39.38%) in all sample types, with a slightly higher percentage in CM (21.84%), followed by SCM (17.65%), and HS (14.38%). S. rostri was also present in all sample types (3.34%), reaching 8.43% of all NASM in SCM and showing a significant association (p < 0.01) with this condition. Based on our findings, the presence of S. borealis and S. rostri in milk and their potential association with mastitis might have been overlooked, possibly due to the difficulties in differentiating these species from other closely related NASM. Our results indicate that S. borealis could be a more frequent contributor to bovine udder infections than previously thought and that S. rostri should also not be underestimated considering its significant association with SCM.

Matrix-Assisted Laser Desorption Ionization Time-of-Flight Mass Spectrometry Combined with Chemometrics for Protein Profiling and Classification of Boiled and Extruded Quinoa from Conventional and Organic Crops

Quinoa is an Andean crop that stands out as a high-quality protein-rich and gluten-free food. However, its increasing popularity exposes quinoa products to the potential risk of adulteration with cheaper cereals. Consequently, there is a need for novel methodologies to accurately characterize the composition of quinoa, which is influenced not only by the variety type but also by the farming and processing conditions. In this study, we present a rapid and straightforward method based on matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) to generate global fingerprints of quinoa proteins from white quinoa varieties, which were cultivated under conventional and organic farming and processed through boiling and extrusion. The mass spectra of the different protein extracts were processed using the MALDIquant software (version 1.19.3), detecting 49 proteins (with 31 tentatively identified). Intensity values from these proteins were then considered protein fingerprints for multivariate data analysis. Our results revealed reliable partial least squares-discriminant analysis (PLS-DA) classification models for distinguishing between farming and processing conditions, and the detected proteins that were critical for differentiation. They confirm the effectiveness of tracing the agricultural origins and technological treatments of quinoa grains through protein fingerprinting by MALDI-TOF-MS and chemometrics. This untargeted approach offers promising applications in food control and the food-processing industry.

Molecular expression, purification and structural characterization of recombinant L-Glutaminase from Streptomyces roseolus

The present research reports the anti-cancer potential of recombinant L-Glutaminase from Streptomyces roseolus. L-Glutaminase gene was synthesized by codon-optimization, cloned and successfully expressed in E. coli BL21 (DE3). Affinity purified recombinant L-Glutaminase revealed a molecular mass of 32 kDa. Purified recombinant L-Glutaminase revealed stability at pH 7.0–8.0 with optimum activity at 70 °C further indicating its thermostable nature based on thermodynamic characterization. Recombinant L-Glutaminase exhibited profound stability in the presence of several biochemical parameters and demonstrated its metalloenzyme nature and was also found to be highly specific towards favorable substrate (l-Glutamine) based on kinetics. It demonstrated antioxidant property and pronounced cytotoxic effect against breast cancer (MCF-7 cell lines) in a dose dependent behavior with IC50 of 40.68 μg/mL. Matrix-assisted laser desorption ionization-time of flight-mass spectroscopy (MALDI-TOF-MS) analysis of desired mass peaks ascertained the recombinant L-Glutaminase identity. N-terminal amino acid sequence characterization through Edman degradation revealed highest resemblance for L-glutaminase within the Streptomyces sp. family. The purified protein was characterized structurally and functionally by employing spectroscopic methods like Raman, circular dichroism and nuclear magnetic resonance. The thermostability was assessed by thermogravimetric analysis. The outcomes of the study, suggests the promising application of recombinant L-Glutaminase as targeted therapeutic candidate for breast cancer.

MALDI-TOF MS profiling and antifungal activity of lactic acid bacteria from kunu aya, a tiger nut traditional beverage of Nigeria

The application of matrix-assisted laser desorption time-of-flight mass spectrometry (MALDI-TOF MS) as a technique for high-throughput characterization of microbiota in African traditional foods is limited. Kunu aya is an unexplored reservoir of protective lactic acid bacteria (LAB) strains. A total of 26 LAB isolates from kunu aya were identified using MALDI-TOF MS as five species, including Lactiplantibacillus plantarum (14), Pediococcus pentosaceus (9), Levilactobacillus brevis (1), Lactiplantibacillus pentosus (1), and Weissella paramesenteroides (1). Antifungal activity screening of all LAB strains by agar-plate overlay assay revealed inhibition against Penicillium crustosum FOO5BA and/or Aspergillus flavus FOO8BA by six strains: L. plantarum (3), Pd. pentosaceus (1), L. brevis (1), and W. paramesenteroides (1). The six LAB strains demonstrated broad spectrum antifungal activity, when tested against eight molds from plant-based foods, inhibiting 4 to 7 molds, with average inhibition scores (AIS) of 0.75–2.75. L. brevis MKAIA1b showed the strongest antifungal activity (AIS; 2.75). Agar diffusion method revealed that antifungal activity against all target molds was retained in cell-free supernatants of L. brevis MKAIA1b, with the highest inhibition demonstrated against P. citrinum 3AS1 (15.34%). In challenged kunu aya fermented with L. brevis MKAIA1b or L. brevis MKAIA1b and L. plantarum TMP051, the growth of A. flavus F008BA, Fusarium langesthiae 13,014, and P. crustosum FOO5BA was delayed beyond 7 days at ambient temperature (25 °C). In this study, MALDI-TOF MS was an effective tool to reveal the species composition of LAB in kunu aya, which harbors LAB strains that displayed strong antifungal activity, while showing great potentials as a protective culture and for bio-control.

Chromosomal and plasmid localization of ileS2 in high-level mupirocin-resistant Staphylococcus pseudintermedius and Staphylococcus aureus isolated from canine and feline origins.

To characterize the mobile genetic elements and genetic localization of ileS2 in high-level mupirocin-resistant (Hi-MupR) methicillin-resistant Staphylococcus pseudintermedius (MRSP) and MRSA isolates recovered from canine and feline clinical samples. The identification of bacterial species and presence of mecA and ileS2 genes in MRSP and MRSA isolates were performed using MALDI-TOF MS and PCR, respectively. Antimicrobial resistance (AMR) phenotypes were determined by broth microdilution assays. The genome characteristics, ileS2-containing elements and staphylococcal cassette chromosome mec (SCCmec) were illustrated using complete circular genomes obtained from hybrid assembly of Illumina short-reads and Oxford Nanopore Technologies long-reads. These were analysed through phylogenetic and bioinformatics approaches. A total of 18 MRSP clinical isolates and four MRSA clinical isolates exhibited the Hi-MupR phenotype and carried multiple AMR genes, including mecA and ileS2 genes. MRSP ST182-SCCmec V (n = 6) and ST282-ΨSCCmec57395-t10 (n = 4) contained the ileS2 transposable unit associated with IS257 on the chromosome. Three MRSA ST398-SCCmec V-t034/t4652 isolates carried ∼42 kb pSK41-like ileS2 plasmids, whereas similar ileS2 plasmids lacking tra genes were found in MRSP ST282-ΨSCCmec57395-t72/t21 isolates. Furthermore, a new group of ileS2 plasmids, carried by MRSP ST45-ΨSCCmec57395, ST433-ΨSCCmecKW21-t05 and ST2165-SCCmec IV-t06, and by one MRSA ST398-SCCmec V-t034 strain, shared the plasmid backbone with the cfr/fexA-carrying plasmid pM084526_1 in MRSA ST398. This study provides the first evidence of ileS2 integration into the S. pseudintermedius chromosome, which is a rare occurrence in staphylococcal species, and plasmids played a pivotal role in dissemination of ileS2 in both staphylococcal species.

A Simple and Rapid Quantitative Assay for Gossypol via Reactive Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry.

The development of simple and rapid analytical tools for gossypol (GSP) is important to the food industry and medical field. Here, we report a matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) method for the detection of GSP by using a reactive matrix 4-hydrazinoquinazoline (4-HQ). The two aldehyde groups of GSP react with the 4-HQ and therefore improve the detection sensitivity and selectivity of GSP. Moreover, GSP forms homogeneous crystals with the 4-HQ matrix, allowing the quantification of the GSP by the proposed method. With the optimized experimental conditions, GSP could be detected at concentrations as low as 0.1 μM and quantified in a wide linear range (1-500 μM). After a brief extraction with an organic solvent, the GSP contents in cottonseeds and cottonseed kernels from different provinces of China were determined successfully. The spiked recovery of GSP in cottonseed/cottonseed kernel samples was obtained as 97.88-105.80%, showing the reliability of the assay for GSP determination in real samples.

Utility of MALDI-TOF MS for determination of species identity and blood meal sources of primary malaria vectors on the Kenyan coast.

Protein analysis using matrix-assisted laser desorption/ionisation time-of-flight mass-spectrometry (MALDI-TOF MS) represents a promising tool for entomological surveillance. In this study we tested the discriminative power of this tool for measuring species and blood meal source of main Afrotropical malaria vectors on the Kenyan coast. Mosquito collections were conducted along the coastal region of Kenya. MALDI-TOF MS spectra were obtained from each individual mosquito's cephalothorax as well as the abdomens of blood-engorged mosquitoes. The same mosquitoes were also processed using gold standard tests: polymerase chain reaction (PCR) for species identification and enzyme linked immunosorbent assay (ELISA) for blood meal source identification. Of the 2,332 mosquitoes subjected to MALDI-TOF MS, 85% (1,971/2,332) were considered for database creation and validation. There was an overall accuracy of 97.5% in the identification of members of the An. gambiae ( An. gambiae, 100%; An. arabiensis, 91.9%; An. merus, 97.5%; and An. quadriannulatus, 90.2%) and An. funestus ( An. funestus, 94.2%; An. rivulorum, 99.4%; and An. leesoni, 94.1%) complexes. Furthermore, MALDI-TOF MS also provided accurate (94.5% accuracy) identification of blood host sources across all mosquito species. This study provides further evidence of the discriminative power of MALDI-TOF MS to identify sibling species and blood meal source of Afrotropical malaria vectors, further supporting its utility in entomological surveillance. The low cost per sample (<0.2USD) and high throughput nature of the method represents a cost-effective alternative to molecular methods and could enable programs to increase the number of samples analysed and therefore improve the data generated from surveillance activities.

Characterization of Leuconostoc lactis Bacteremia during a 2-year Study at a Tertiary Care Center in North India-An Observational Analysis.

Leuconostoc species are regarded as important causes for many infections in immunocompromised patients. In this study, we assessed the characteristics of Leuconostoc spp. causing bacteremia in patients at our center. This observational analysis was conducted in the microbiology laboratory of a tertiary care center in northern India from July 2021 to July 2023. Patients in whom blood culture bottles were positive for Leuconostoc lactis were included in the study. Culture isolates were identified by MALDI-ToF MS as L. lactis and tested for antibiotic sensitivity results by Kirby-Bauer disk diffusion method. Demographic and clinical details were collected and analyzed. During the study period, 6,742 blood culture bottles flagged positive. Among these, L. lactis was isolated from 14 (0.21%) patients. The median patient age was 34 years. The male-to-female ratio was 2.5:1. All the patients with L. lactis bacteremia had an underlying condition leading to immunosuppression (e.g., carcinoma and chronic kidney disease). All the patients with L. lactis bacteremia had an intravascular device present at the time of bacteremia. All isolates in the study were sensitive to doxycycline, high level gentamicin, minocycline, ampicillin-sulbactam, and linezolid. Mortality was attributed to bacteremia by L. lactis in five patients. Appropriate and timely identification of the Leuconostoc species is important for the clinician to tailor regimens for the patients.