Characterization of different food‐isolated Enterococcus strains by MALDI‐TOF mass fingerprinting

Abstract

Enterococcus is a controversial genus due to its great variability; this genus includes pathogenic strains, spoilage strains, and apparently safe strains including some probiotic strains. Previous studies focused on the characterization of strains of Enterococcus spp. involved in nosocomial infections. However, little research has been conducted on Enterococcus strains in foodstuffs. In the present work, 36 strains of different species of Enterococcus have been characterized by means of MALDI-TOF MS, resulting in highly specific mass spectral fingerprints. Characteristic peak masses common to certain bacterial species of Enterococcus have been identified. Thus, a peak at m/z 4426 ± 1 was assigned as a genus-specific biomarker. In addition, phyloproteomic relationships based on the mass spectral data were compared to the results of a phylogenetic analysis based on the 16S rRNA gene sequence. A better grouping at the species level was observed in the phyloproteomic tree, especially for the Enterococcus faecium group. Presumably, the assortment of some strains or ecotypes could be related to their ecological niche specialization. The approach described in this study leads the way toward the rapid and specific identification of different strains and species of Enterococcus in food based on molecular protein markers, aiming at the early detection of pathogenic strains and strains implicated in food poisoning or food spoilage.

Use of MALDI-TOF mass spectrometry fingerprinting to characterize Enterococcus spp. and Escherichia coli isolates

“…However, the efficiency and reproducibility of MALDI-TOF MS in distinguishing enterococci species need to be evaluated. Our genus and species-specific mass peak results are similar to those obtained by Quintela-Baluja et al [10]. The identification of protein biomarkers is an important step to facilitate the rapid identification of the genus and species of a particular isolate, but unique peaks and having only a few different isolates of the same species are also crucial for the bacterial classification of unknown samples.…”

“…As in another study by Quintela-Baluja et al, a peak at m/z 4428 Da ± 3 was detected in all spectra from Enterococcus spp. [10]. The presence of this mass peak in Fig.…”

“…During the last two decades, these two bacterial genera have gained notoriety in medicine, as they are now commonly associated with several human infections in addition to causing various animal diseases. Enterococcus faecalis and Enterococcus faecium are the most common Enterococcus species associated with human infections [10]. Recent reports identify these bacteria as a major cause of infections of the urinary tract and bloodstream of patients in intensive care units.…”

Advanced Mass Spectrometry

“…Enterococcus strains by fingerprinting [138] MALDI-TOF Rapid identification of microorganisms isolated from pickled vegetables [139] MALDI-TOF Characterization and profiling of Bacillus subtilis, Bacillus cereus, and Bacillus licheniformis by mass fingerprinting [140] MALDI-TOF Rapid and accurate bacterial identification in probiotics and yogurts [141] MALDI-TOF Species identification of Aspergillus section Flavi isolates from Portuguese almonds using phenotypic [142] MALDI-TOF Identification and classification of seafoodborne pathogenic [143] MALDI-TOF Assessment of seafood safety and quality by rapid identification of pathogenic and spoilage bacterial species by fingerprinting [144] MALDI-TOF Rapid identification of Tetragenococcus halophilus and Tetragenococcus muriaticus, important species in the production of salted and fermented food [145] Volatile Compounds PTR-TOF Rapid characterization of dry cured ham produced following different PDOs [146] PTR-TOF Linking GC-MS and PTR-TOF-MS fingerprints of food samples [147] Much less used, the IT-TOF combines ion trap and TOF technologies. When combining IT and TOF, the greatest technological challenges were the efficient introduction of ions into the IT and the simultaneous ejection of trapped ions to the TOF.…”

MALDI-TOF mass spectroscopy of yeasts and filamentous fungi for research and diagnostics in the agricultural value chain

“…MALDI-TOF MS is also highly flexible and can be combined with additional extraction or processing steps in order to identify specific biomarkers, metabolites, or biochemical functions. Because of these advantages, MALDI biotyping has become a standard in routine clinical diagnostics and MALDI-TOF MS devices have become readily accessible, also for researchers in other disciplines than clinical diagnostics [4,13,14]. This opens up new possibilities for functional hypothesis-driven research.…”