Rapid and Accurate Bacterial Identification in Probiotics and Yoghurts by MALDI‐TOF Mass Spectrometry

Abstract

Probiotic food is manufactured by adding probiotic strains simultaneously with starter cultures in fermentation tanks. Here, we investigate the accuracy and feasibility of matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS) for bacterial identification at the species level in probiotic food and yoghurts. Probiotic food and yoghurts were cultured in Columbia and Lactobacillus specific agar and tested by quantitative real-time PCR (qPCR) for the detection and quantification of Lactobacillus sp. Bacterial identification was performed by MALDI-TOF analysis and by amplification and sequencing of tuf and 16S rDNA genes. We tested 13 probiotic food and yoghurts and we identified by qPCR that they presented 10(6) to 10(7) copies of Lactobacillus spp. DNA/g. All products contained very large numbers of living bacteria varying from 10(6) to 10(9) colony forming units/g. These bacteria were identified as Lactobacillus casei, Lactococcus lactis, Bifidobacterium animalis, Lactobacillus delbrueckii, and Streptococcus thermophilus. MALDI-TOF MS presented 92% specificity compared to the molecular assays. In one product we found L. lactis, instead of Bifidus spp. which was mentioned on the label and for another L. delbrueckii and S. thermophilus instead of Bifidus spp. MALDI-TOF MS allows a rapid and accurate bacterial identification at the species level in probiotic food and yoghurts. Although the safety and functionality of probiotics are species and strain dependent, we found a discrepancy between the bacterial strain announced on the label and the strain identified. Practical Application: MALDI-TOF MS is rapid and specific for the identification of bacteria in probiotic food and yoghurts. Although the safety and functionality of probiotics are species and strain dependent, we found a discrepancy between the bacterial strain announced on the label and the strain identified.

Identification of Rare Pathogenic Bacteria in a Clinical Microbiology Laboratory: Impact of Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry

“…Detection of antimicrobial resistance using MALDI-TOF MS has been reported for Staphylococcus aureus (25)(26)(27)(28)(29)(30)(31)(32), Acinetobacter baumannii (26), Escherichia coli, and other members of the family Enterobacteriaceae (33)(34)(35). Several new bacterial species emerging as human pathogens have been identified using MALDI-TOF MS (36)(37)(38)(39)(40)(41)(42)(43)(44)(45).…”

Evaluation of Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry for Rapid Identification of Bacteria in Processed Soybean Products

“…At a lower bacterial count (< 10 6 CFU/ml), background peaks became more prominent and affected spectrum matching. Although MALDI-TOF MS may become a popular identification method in food microbiology, there is little information on direct identification of bacteria in processed food products using MALDI-TOF MS (Angelakis et al, 2011;Böhme et al, 2011;Hochel et al, 2012). The separation of bacteria is conducted to harvest cells from complex food matrices that impede accurate detection (Benoit & Donahue 2003;Stevens & Jaykus, 2004).…”

The role of gut microbiota in the gut-brain axis: current challenges and perspectives

“…MALDI-TOF MS allows the identifi cation of various micro-organisms by so called intact-cell mass spectrometry and the comparison of a sample's mass spectrum to reference mass spectra in a database. The key factors to the success of this technology are the fact that a uniform sample preparation procedure is utilized for many different types of micro-organisms, comparatively low cost and short time per analysis (Angelakis et al, 2011). Additionally, MS-based identifi cation can be readily expanded to different microbiological fi elds, including food, industrial and veterinary microbiology.…”

“…There has been discrepancy between the bacterial strain announced on the label on commercial product and strain identifi ed using MALDI-TOF. MS presented 92% specifi city compared to molecular assay and additional species were identifi ed (Angelakis et al, 2011). Albesharat et al have performed studies on microbial diversity using RAPD, which was further characterized by MALDI-TOF MS with better clustering result (Albesharat et al, 2011).…”