The use of principle component analysis and MALDI-TOF MS for the differentiation of mineral forming <i>Virgibacillus</i> and <i>Bacillus</i> species isolated from sabkhas

et al. 2021

Foods

Rapid detection of Salmonella serovars is important for the effective control and monitoring of food industries. In this study, we evaluate the application of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry for the rapid detection of three serovars, Enteritidis, Typhimurium, and Thompson, that are epidemiologically important in Korea. All strains were identified at the genus level, with a mean score of 2.319 using the BioTyper database, and their protein patterns were confirmed to be similar by principal component analysis and main spectrum profile dendrograms. Specific peaks for the three serovars were identified by analyzing 65 reference strains representing 56 different serovars. Specific mass peaks at 3018 ± 1 and 6037 ± 1, 7184 ± 1, and 4925 ± 1 m/z were uniquely found in the reference strains of serovars Enteritidis, Typhimurium, and Thompson, respectively, and they showed that the three serovars can be differentiated from each other and 53 other serovars. We verified the reproducibility of these mass peaks in 132 isolates, and serovar classification was achieved with 100% accuracy when compared with conventional serotyping through antisera agglutination. Our method can rapidly detect a large number of strains; hence, it will be useful for the high-throughput screening of Salmonella serovars.

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Rapid Detection of Salmonella Enteritidis, Typhimurium, and Thompson by Specific Peak Analysis Using Matrix-Assisted Laser Desorption Ionization Time-of-Flight Mass Spectrometry

Yang

et al. 2021

Foods

“…Five reference strains and 60 isolates were used to evaluate MALDI-TOF MS robustness. The main spectrum profile dendrogram and PCA clustering are practical for differentiating between closely related strains and determining associations between isolated strains [ 32 ]. Dendrogram and PCA clustering were performed to confirm the discriminative power of mass spectra to identify two species; all E .…”

Section: Resultsmentioning

confidence: 99%

Differentiating between Enterococcusfaecium and Enterococcuslactis by Matrix-Assisted Laser Desorption Ionization Time-of-Flight Mass Spectrometry

Yang

et al. 2022

Foods

Unlike Enterococcus faecium strains, some Enterococcus lactis strains are considered potential probiotic strains as they lack particular virulence and antibiotic resistance genes. However, these closely related species are difficult to distinguish via conventional taxonomic methods. Here, for the first time, we used matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) with BioTyper and in-house databases to distinguish between E. faecium and E. lactis. A total of 58 reference and isolated strains (89.2%) were correctly identified at the species level using MALDI-TOF MS with in-house databases. However, seven strains (10.8%) were not accurately differentiated as a single colony was identified as a different species with a similar score value. Specific mass peaks were identified by analyzing reference strains, and mass peaks at 10,122 ± 2 m/z, 3650 ± 1 m/z, and 7306 ± 1 m/z were unique to E. faecium and E. lactis reference strains, respectively. Mass peaks verified reproducibility in 60 isolates and showed 100% specificity, whereas 16S rRNA sequencing identified two different candidates for some isolates (E. faecium and E. lactis). Our specific mass peak method helped to differentiate two species, with high accuracy and high throughput, and provided a viable alternative to 16S rRNA sequencing.

“…The mass spectra generated from MALDI-TOF MS are regarded as multivariate data, in which every mass signal represents a single molecular dimension. Therefore, multivariate statistical methods are generally used for differentiation between bacterial species (Samad et al, 2020). Accordingly, the mass spectra obtained in this study were further analyzed to determine the composite correlation index (CCI) which was used to statistically determine the relationship between the acquired spectra.…”

Section: Mass Spectrum Profile and Phyloproteomic Pca Analysis Of S Aureus And Other Staphylococcimentioning

confidence: 99%

The efficiency of MALDI-TOF MS method in detectingStaphylococcus aureusisolated from raw milk and artisanal dairy foods

Taban

Cevik

2021

CyTA - Journal of Food

The present study aims to characterize twenty-seven Staphylococcus aureus isolates among a total of forty-four Staphylococci recovered from raw milk and traditional artisanal dairy foods (n = 285) in Central Anatolia and the Mediterranean Regions of Turkey, using MALDI-TOF MS-based phyloproteomic principal component analysis (PCA). The data shown by the spectra were analyzed, followed by composite correlation index (CCI), virtual gel, and cluster analysis for validation. The correlation between standard strain S. aureus 25,923 THL (SA-18) and all strains was significant since protein peak of m/z 5305 ± 2 Da was common in all strains, including SA-18. Twenty-six (9.12%) and fifteen (5.26%) out of all samples were found as contaminated by Staphylococci and S. aureus, respectively. The findings suggest that MALDI-TOF MS-based PCA is a promising fast method to categorize S. aureus in dairy foods, in need of continuous monitoring of foodborne pathogens for public health. Eficacia del método EM MALDI-TOF para la detección de Staphylococcus aureus aislados de leche cruda y alimentos lácteos artesanalesEl presente estudio tuvo por objeto caracterizar 27 aislados de Staphylococcus aureus entre un total de 44 estafilococos recuperados de leche cruda y alimentos lácteos artesanales tradicionales (n=285) en Anatolia Central y las regiones mediterráneas de Turquía. Para ello se utilizó el análisis de componentes principales (PCA) filoproteómico, basado en la EM MALDI-TOF. Se analizaron los datos mostrados por los espectros, seguidos por el índice de correlación compuesto (CCI), el gel virtual y el análisis de clúster para su validación. Se constató que la correlación entre la cepa estándar S. aureus 25923 THL (SA-18) y todas las cepas fue significativa, ya que el pico proteico de m/z 5305 ± 2 Da fue común a todas ellas, incluida la SA-18. De todas las muestras analizadas, 26 (9.12%) resultaron contaminadas por estafilococos y 15 (5.26%) por S. aureus. Los resultados dan cuenta de que el PCA basado en la EM MALDI-TOF es un método rápido y prometedor para categorizar S. aureus en los alimentos lácteos que requieren, para garantizar la salud pública, un seguimiento continuo de los patógenos transmitidos por los alimentos.