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- ItemDetermining the location of Co2+ in zeolites by UV-Vis diffuse reflection spectroscopy : A critical view(Basel : MDPI, 2020) Bellmann, Andrea; Rautenberg, Christine; Bentrup, Ursula; Brückner, AngelikaUV-Vis spectroscopy as well as in situ FTIR spectroscopy of pyridine and CO adsorption were applied to determine the nature of Co species in microporous, mesoporous, and mixed oxide materials like Co-ZSM-5, Co/Na-ZSM-5, Co/Al-SBA-15, and Co/Al2O3-SiO2. Because all sample types show comparable UV-Vis spectra with a characteristic band triplet, the former described UV-Vis band deconvolution method for determination and quantification of individual cationic sites in the zeolite appears doubtful. This is also confirmed by results of pyridine and CO adsorption revealing that all Co-zeolite samples contain two types of Co2+ species located at exchange positions as well as in oxide-like clusters independent of the Co content, while in Co/Al-SBA-15 and Co/Al2O3-SiO2 only Co2+ species in oxide-like clusters occur. Consequently, the measured UV-Vis spectra represent not exclusively isolated Co2+ species, and the characteristic triplet band is not only related to γ-, β-, and α-type Co2+ sites in the zeolite but also to those dispersed on the surface of different oxide supports. The study demonstrates that for proper characterization of the formed Co species, the use of complementary methods is required. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.
- ItemCharacterization of antibiotic and biocide resistance genes and virulence factors of staphylococcus species associated with bovine mastitis in Rwanda(Basel : MDPI AG, 2020) Antók, Fruzsina Irén; Mayrhofer, Rosa; Marbach, Helene; Masengesho, Jean Claude; Keinprecht, Helga; Nyirimbuga, Vedaste; Fischer, Otto; Lepuschitz, Sarah; Ruppitsch, Werner; Ehling-Schulz, Monika; Feßler, Andrea T.; Schwarz, Stefan; Monecke, Stefan; Ehricht, Ralf; Grunert, Tom; Spergser, Joachim; Loncaric, IgorThe present study was conducted from July to August 2018 on milk samples taken at dairy farms in the Northern Province and Kigali District of Rwanda in order to identify Staphylococcus spp. associated with bovine intramammary infection. A total of 161 staphylococcal isolates originating from quarter milk samples of 112 crossbred dairy cattle were included in the study. Antimicrobial susceptibility testing was performed and isolates were examined for the presence of various resistance genes. Staphylococcus aureus isolates were also analyzed for the presence of virulence factors, genotyped by spa typing and further phenotypically subtyped for capsule expression using Fourier Transform Infrared (FTIR) spectroscopy. Selected S. aureus were characterized using DNA microarray technology, multi-locus sequence typing (MLST) and whole-genome sequencing. All mecA-positive staphylococci were further genotyped using dru typing. In total, 14 different staphylococcal species were detected, with S. aureus being most prevalent (26.7%), followed by S. xylosus (22.4%) and S. haemolyticus (14.9%). A high number of isolates was resistant to penicillin and tetracycline. Various antimicrobial and biocide resistance genes were detected. Among S. aureus, the Panton–Valentine leukocidin (PVL) genes, as well as bovine leukocidin (LukM/LukF-P83) genes, were detected in two and three isolates, respectively, of which two also carried the toxic shock syndrome toxin gene tsst-1 bovine variant. t1236 was the predominant spa type. FTIR-based capsule serotyping revealed a high prevalence of non-encapsulated S. aureus isolates (89.5%). The majority of the selected S. aureus isolates belonged to clonal complex (CC) 97 which was determined using DNA microarray based assignment. Three new MLST sequence types were detected. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.