Evaluation of Fourier transform infrared spectroscopy for the rapid identification of glycopeptide-intermediate Staphylococcus aureus

Objectives To evaluate Fourier transform infrared (FTIR) spectroscopy as a rapid method for distinguishing glycopeptide-intermediate Staphylococcus aureus (GISA) from glycopeptide-susceptible methicillin-resistant S. aureus (MRSA) and to compare three data analysis methods. Methods First-derivative normalized spectra of dried films of bacterial growth on Que-Bact® Universal Medium No. 2 were examined by singular value decomposition to identify key spectral regions. Region selection was analysed by principal component analysis (PCA), self-organizing maps (SOMs) and the K-nearest neighbour (KNN) algorithm. The initial data set included 35 GISA (including GISA Mu50 and heterogeneous GISA Mu3) and 25 epidemic MRSA. The regions were then tested using enlarged data sets that included 22 sporadic and 85 additional epidemic MRSA. Results Epidemic MRSA and GISA/hGISA were separated into two distinct clusters on the basis of spectral data from regions 1352-1315 and 1480-1460 cm−1, the former providing 100% correct classification by all three analyses and the latter providing 96.67% correct by PCA, 98.34% by SOM and 100% by KNN. The 1480-1460 cm−1 region was more effective for distinguishing GISA/hGISA from a set combining sporadic and epidemic MRSA, with two GISA/hGISA and four sporadic MRSA misclassified by PCA and SOM (92.69% correct), while the KNN method misclassified three of the four sporadic MRSA (93.90% correct). The addition of 85 other epidemic MRSA this set increased the fraction of correctly classified isolates to 96.41% and 97.01% by PCA, SOM and KNN, respectively. Conclusions As only 6 of 167 isolates were misclassified, FTIR spectroscopy may provide means of rapid and accurate identification of GISA and hGISA among isolates of MRS

Efficient extraction of hydrophilic and lipophilic antioxidants from microalgae with supramolecular solvents

There is strong evidence that lipophilic and hydrophilic antioxidants interact in vivo through different mechanisms and that it is their mixed effects what leads to health benefits. Simultaneous extraction of both types of antioxidants from biomass using organic solvents is inefficient because extraction yields for these phytochemicals are highly dependent on the polarity of the solvent. In this work, we firstly propose the use of supramolecular solvents (SUPRAS) as an innovative approach for the simultaneous extraction of a wide polarity range of antioxidants. Different SUPRAS compositions were investigated for extraction of the total content of carotenoids and polyphenols, as representatives of lipophilic and hydrophilic antioxidants, respectively. Under optimal conditions, antioxidants were extracted from freeze-dried biomass of Scenedesmus sp. in an excellent rate related to their total content (up to 1 mg carotenoids/g dw and 10 mg of gallic acid equivalents, GAE/g dw). Screening based on liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) revealed that lutein was the major carotenoid and caffeic acid the main phenolic compound. The SUPRAS extracts showed high antioxidant activity (25.04 ± 0.73 µM ascorbic acid equivalents antioxidant capacity, AAAC/g dw and 17.02 ± 0.45 µM AAAE/g dw for ABTS and DPPH assays, respectively). SUPRAS offered advantages in terms of non-toxicity, rapidity (5 min extraction) and cost-effectiveness (room temperature, atmospheric pressure) for the recovery of antioxidant compounds from algal biomass and constitute a good alternative to the use of conventional solvents