Odor-Reduced HDPE-Lignin Blends by Use of Processing Additives.

The comprehensive use of natural polymers, such as lignin, can accelerate the replacement of mineral oil-based commodities. Promoting the material recovery of the still underutilized technical lignin, polyolefin-lignin blends are a highly promising approach towards sustainable polymeric materials. However, a limiting factor for high-quality applications is the unpleasant odor of technical lignin and resulting blends. The latter, especially, are a target for potential odor reduction, since heat- and shear-force intense processing can intensify the smell. In the present study, the odor optimization of kraft and soda HDPE-lignin blends was implemented by the in-process application of two different processing additives-5% of activated carbon and 0.7% of a stripping agent. Both additives were added directly within the compounding process executed with a twin screw extruder. The odor properties of the produced blends were assessed systematically by a trained human panel performing sensory evaluations of the odor characteristics. Subsequently, causative odor-active molecules were elucidated by means of GC-O and 2D-GC-MS/O while OEDA gave insights into relative odor potencies of single odorants. Out of 70 different odorants detected in the entirety of the sample material, more than 30 sulfur-containing odorants were present in the kraft HDPE-lignin blend, most of them neo-formed due to high melt temperatures during extrusion, leading to strong burnt and sulfurous smells. The addition of activated carbon significantly decreased especially these sulfurous compounds, resulting in 48% of overall odor reduction of the kraft blend (mean intensity ratings of 5.2) in comparison to the untreated blend (10.0). The applied stripping agent, an aqueous solution of polymeric, surface-active substances adsorbed onto a PP carrier, was less powerful in reducing neo-formed sulfur odorants, but led to a decrease in odor of 26% in the case of the soda HDPE-lignin blend (7.4). The identification of single odorants on a molecular level further enabled the elucidation of odor reduction trends within single compound classes. The obtained odor reduction strategies not only promote the deodorization of HDPE-lignin blends, but might be additionally helpful for the odor optimization of other natural-fiber based materials.

Rapid identification of clinically relevant Enterococcus species by fluorescence in situ hybridization.

A fluorescence in situ hybridization assay for the rapid identification of clinically relevant enterococci (Enterococcus faecalis, E. faecium, E. gallinarum, the VanC-type resistance group) was developed and evaluated with 33 reference strains, 68 clinical isolates, and 58 positive blood cultures. All probes showed excellent sensitivities and specificities.

Detection of mutations conferring resistance to linezolid in Enterococcus spp. by fluorescence in situ hybridization.

A fluorescence in situ hybridization (FISH) assay was established to detect linezolid resistance (conferred by the mutation 2576G>T in the gene coding for the 23 string of the ribosomal RNA) in enterococci. The assay was evaluated with 106 Enterococcus isolates; it showed a sensitivity of 100% for the detection of phenotypic resistance and was even able to identify a single mutated allele in phenotypically linezolid-susceptible isolates.

Evaluation of the Merlin MICRONAUT system for rapid direct susceptibility testing of gram-positive cocci and gram-negative bacilli from positive blood cultures.

Bloodstream infections are life-threatening conditions which require the timely initiation of appropriate antimicrobial therapy. We evaluated the automated Merlin MICRONAUT system for rapid direct microtiter broth antimicrobial susceptibility testing (AST) of gram-positive cocci and gram-negative bacilli from BACTEC 9240 bottles with positive blood cultures in comparison to the standard method for the Merlin MICRONAUT system. This prospective study was conducted under routine working conditions during a 9-month period. Altogether, 504 isolates from 409 patients and 11,819 organism-antibiotic combinations were evaluated for comparison of direct and standard AST methods. For gram-negative bacilli, direct and standard AST of 110 isolates was evaluated and MIC agreement was found for 98.1% of 2,637 organism-antibiotic combinations. Category (susceptible, intermediate susceptible, resistant [SIR]) agreement was found for 99.0%, with results for 0.04% of combinations showing very major errors, those for 0.2% showing major errors, and those for 0.8% showing minor errors. For gram-positive cocci, 373 isolates were evaluated and MIC agreement was found for 95.6% of 8,951 organism-antibiotic combinations. SIR agreement was found for 98.8%, with results for 0.3% of combinations showing very major errors, those for 0.4% showing major errors, and those for 0.5% showing minor errors. Although the number of tested isolates was limited (n = 33), direct AST of streptococci was performed for the first time, yielding promising results with SIR agreement for 98.6% of 363 organism-antibiotic combinations. In conclusion, direct AST of gram-negative bacilli and gram-positive cocci from positive blood cultures with the MICRONAUT system is a reliable technique that allows for the omission of repeat testing of subcultured isolates. Thereby, it reduces the time to results of blood culture testing and may have a positive impact on patient care.

Rapid detection of Brucella spp. in blood cultures by fluorescence in situ hybridization.

Brucellosis is a severe systemic disease in humans. We describe a new 16S rRNA-based fluorescence in situ hybridization assay that facilitates rapid and specific detection of all human pathogenic species of Brucella and that can be applied directly to positive blood cultures.