Test for the Production and Assay of the Proteolytic Activities of Halophilic Bacteria and Archaea Isolated from Algerian Hypersaline Environments

: The present work was carried out on 133 halophilic strains isolated on MGM (Modified Growth Medium) medium with 12 and 23% (w/v) of salt. A screening of the extracellular proteolytic activities, carried out on the same medium supplemented with casein or gelatin at 1% (w/v), allowed us to select 24 bacterial and 21 archaeal strains presenting a precipitate around the colonies for casein and/or a translucent halo (after addition of Frazier’s reagent) for gelatin. The enzymatic test was performed on liquid medium in microculture in a 2 mL Eppendorf tube. The assay of the proteolytic activity, using Azocasein as substrate, followed two protocols—the first with PBS and the second with Tris HCl, with positive and negative controls—and demonstrated interesting results for 10 strains among the 45 tested including five bacteria and five archaea. These underwent morphological, physiological and molecular characterizations based on amplification and sequencing of the 16S ribosomal RNA gene.

Red Wine Oxidation: Accelerated Ageing Tests, Possible Reaction Mechanisms and Application to Syrah Red Wines

Wine oxidation and ageing involve many complex chemical pathways and reaction mechanisms. The purpose of this study is to set up new and reproducible accelerated red wine ageing tests and identify chemical oxidation or ageing molecular markers. Three accelerated and reproducible ageing tests were developed: a heat test (60 °C); an enzymatic test (laccase test; a chemical test (hydrogen peroxide test). Depending on the test, oxygen consumption was significantly different. For a young wine (2018), the oxygen consumption rate moved from 2.40 ppm·h−1 for the heat test to 3.33 ppm·h−1 for the enzymatic test and 2.86 ppm·h−1 for the chemical test. Once applied to two other vintages (2010 and 2014) from the same winery, the tests revealed different comportments corresponding to wine natural evolution. High resolution UPLC-MS was performed on forced ageing samples and compared to naturally aged red wines. Specific oxidation or ageing ion markers were found with significant differences between tests, revealing the specificity of each test and different possible molecular pathways involved. The hydrogen peroxide test seems to be closer to natural oxidation with an important decrease in absorbance at 520 nm and similar molecular ion variations for [M+H]+ = 291, 331, 347, 493, 535, 581, 639 Da.

OP106 The Xpert™ Clostridium difficile Kit Incorporation: Conducting a Local Clinical Study as Part of Hospital Health Technology Assessment

IntroductionThe Xpert™ Clostridium difficile kit is a nucleic acid amplification test indicated after discrepant results from an enzymatic test; was submitted for incorporation in a teaching hospital in Brazil. In order to evaluate the potential for improvement with Xpert™ incorporation, the performance of the available technology (enzymatic test) was assessed using a real word evidence approach. Additionally, the association between enzymatic test results and the agreement to the Infectious Diseases Society of America (IDSA) recommendations for stool test submission (≥ 3 unformed stools in 24 hours without laxatives) for Clostridium difficile were evaluated.MethodsThis is a retrospective cohort study conducted at a tertiary teaching hospital. We included all consecutive tested patients that were submitted for enzyme immunoassay – glutamate dehydrogenase (GDH) plus toxin detection from 15 March to 8 May 2018. Data referent to episodes of unformed stools in 24 hours and use of laxatives were recorded. Statistical significance was tested by Fisher Exact test (α = 0.05).ResultsOne hundred and thirty-eight consecutive patients were tested: 4 (2.9 percent) were positive for GDH and toxin (group III); 114 (82.6 percent) were negative for both (group I). Twenty (14.5 percent) cases were discrepant, all being positive to GDH and negative for toxin (group II). There were not negative GDH and positive toxin cases. The IDSA guidelines were followed in 33 (28.9%), 3 (15%) and 3(75%) test orders in groups I, II and III, respectively (p = 0.03).ConclusionsOnly a minority of patients had discrepant results in enzymatic tests and would be candidates for the Xpert™ test. The low adherence to IDSA guidelines could explain the low positivity rate of enzymatic tests at the hospital. Considering the uncertainty about the potential of the new test for changing infection control practices, Xpert™ was not recommended for incorporation. Using real world evidence data is important for contextualized health technology studies in hospitals.

Effect of SiO2 particles on the biodegradability of starch/PVA blends

The present work aimed to study the SiO2μPs, and NPs effect on the biodegradability of St/PVA blends. The samples were prepared by casting method as PVA, St/PVA blends with different concentrations (30, 40, 50, and 60 %). FTIR test was carried out for the samples preparation. The results proved some changes which might be related to changing in crystallinity of St/PVA matrix as well as physical incorporation of SiO2 μPs, and NPs addition. The enzymatic test and water uptake results proved that increase in weight loss with increases of starch ratio. The lowest weight loss was PVA; the highest weight loss is 60% St/PVA whereas the lowest weight loss is 30%St/PVA for blends involved. SiO2μPs (753.7 nm), and NPs (263.1 nm) were added at different concentrations (1.5, 2, and 2.5 %). 1.5% SiO2 μPs, and NPs were the lowest weight loss then it was increased by SiO2μPs, and NPs addition. The samples were investigated with optical microscope. It was concluded that the samples involved could be used as packaging materials for medical application and its degradation could be controlled by SiO2μPs, and NPs addition.

Determination of Ethanol in Kombucha, Juices, and Alcohol-Free Beer by EnzytecTMLiquid Ethanol: Single-Laboratory Validation, First Action 2017.07

EnzytecTMLiquid Ethanol is an enzymatic test for the determination of ethanol in kombucha, juices, and alcohol-free beer. The kit contains two components in a ready-to-use format. Quantification is based on the catalytic activity of alcohol dehydrogenase, which oxidizes ethanol to acetaldehyde and converts NAD+ to NADH. Measurement is performed in 3 mL cuvettes at 340 nm within 20 min. Samples with alcohol contents around 0.5% alcohol by volume need to be diluted 1:20 or 1:50 with water before measurement. Acetaldehyde interferes at concentrations higher than 3000 mg/L, whereas sulfite interferes at concentrations higher than 300 mg/L. The linear measurement range is from 0.03 up to 0.5 g/L ethanol, whereas LOD and LOQ are 1.9 and 3.3 mg/L ethanol, respectively. Kombucha with concentrations between 2.85 and 5.82 g/L showed relative repeatability standard deviation around 1%, whereas juices were below 2%. Results from a reproducibility experiment revealed that at a concentration of 0.1 g/L, the RSDR was at 2.5%, whereas at higher concentrations between 0.2 and 0.3 g/L, coefficients around 1% were obtained. Trueness was checked by using Cerilliant aqueous ethanol solutions and beer with concentration of 0.4 and 4 g/L (BCR-651 and BCR-652). Spiking of kombucha and juice samples resulted in recoveries between 95% and 104%. Acceptable stability was found for the whole test kit under accelerated conditions at 37°C for 2 weeks. The kit is also not susceptible to short freezing–thawing cycles and harsh transport conditions.

EVALUATION OF FOUR PHENOTYPIC TESTS FOR THE DETECTION OF OXA-48-TYPE CARBAPENEMASE IN ENTEROBACTERIACEAE

Carbapenemase-producing Enterobacteriaceae have the potential to rapid dissemination in healthcare settings, becoming a major infection control and public health concern. PCR remains the reference method for identifying these strains, but is still expensive. We evaluated the performance of four phenotypic tests for identifying OXA-48-producing (Oxacillinase-48) Enterobacteriaceae. These were modified Hodge test (MHT), a combination disk test with meropenem alone or in combination with various inhibitors and temocillin, an enzymatic test and an immunochromatographic test. The tests were performed and interpreted according to guidelines or manufacturer’s recommendations. The most frequent microorganism included in the study was Klebsiella pneumoniae. All the tests had 100% specificity, except MHT (87,5%). Sensitivity was 91,25% for MHT, 90% for the combination disk test, 95% for the enzymatic test and 82,50% for the immunochromatographic test.