Evaluation of the influence of the cultivation medium on the result of identification of microorganisms from the group of acid-resistant bacteria of the order actinomycetales by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

Background: Problem with mass spectrometers is the difficulty in identifying some genera of acid-fast bacteria (AFB). Due to the peculiarities of the colony architectonics (the formation of dry colonies with a complex structure) and the structure of the cell wall, the probability of obtaining a sufficient amount of ribosomal proteins is significantly reduced. This problem is partially solved using an extended method of direct application and extraction with formic acid, which can significantly improve the quality of the identification. Methods: The study analyzed strains of microorganisms obtained during the examination of patients with suspected tuberculosis. In total, 287 strains of nontuberculous mycobacteria (NTM) were obtained. In addition, 63 strains of the most common bacteria from the AFB group were analyzed. Matrix-assisted laser desorption/ionization (MALDI) was used. Three main methods of sample preparation of microorganisms according to the manufacturer's recommendations for use with the MALDI-time-of-flight (ToF) mass spectrometry method were used in the work: Direct coating method, extended direct coating method, and formic acid extraction method. Results: When evaluating the influence of the cultivation medium on the result of NTM identification by MALDI-ToF mass spectrometry, statistically significant results of the influence of the medium on the result of NTM identification were revealed for all compared parameters. Conclusions: Optimization of sample preparation protocols and assessment of the impact on the identification of new methods of cultivating microorganisms can significantly improve the quality of the identification of both clinically significant microorganisms from the AFB group and saprophytic microflora, the clinical significance of which has not been proven at the moment.

Development of a novel mathematical model that explains SARS-CoV-2 infection dynamics in Caco-2 cells.

Mathematical modeling is widely used to study within-host viral dynamics. However, to the best of our knowledge, for the case of SARS-CoV-2 such analyses were mainly conducted with the use of viral load data and for the wild type (WT) variant of the virus. In addition, only few studies analyzed models for in vitro data, which are less noisy and more reproducible. In this work we collected multiple data types for SARS-CoV-2-infected Caco-2 cell lines, including infectious virus titers, measurements of intracellular viral RNA, cell viability data and percentage of infected cells for the WT and Delta variants. We showed that standard models cannot explain some key observations given the absence of cytopathic effect in human cell lines. We propose a novel mathematical model for in vitro SARS-CoV-2 dynamics, which included explicit modeling of intracellular events such as exhaustion of cellular resources required for virus production. The model also explicitly considers innate immune response. The proposed model accurately explained experimental data. Attenuated replication of the Delta variant in Caco-2 cells could be explained by our model on the basis of just two parameters: decreased cell entry rate and increased cytokine production rate.

Ionic Transport in CsNO2-Based Nanocomposites with Inclusions of Surface Functionalized Nanodiamonds.

Composite solid electrolytes (1-x) CsNO2-xND, where ND are nanodiamonds, including those after liquid-phase and gas-phase oxidation and reduction functionalization, were prepared, and their properties investigated by XRD, analysis of BET nitrogen adsorption isotherms, IR spectroscopy and impedance spectroscopy. The electrical conductivity of composites (1-x) CsNO2-xND obeys the Arrhenius dependence and has a maximum at x = 0.95 regardless of the ND pretreatment. It was found that the conductivity depends on the mode of functionalization of the ND surface, as well as on the processing time. The electrical conductivity of composites with ND, processed by the gas-phase method, is 1.5-2.6 times higher than that of composites with initial ND, in which the conductivity is 2 orders of magnitude higher than that of pure cesium nitrate. Thus, the possibility of using ND as an effective heterogeneous additive for the preparation of composite solid electrolytes, including cesium nitrite, has been demonstrated for the first time.

Influence of a backward reflection on low-threshold mode instability in Yb3+-doped few-mode fiber amplifiers.

An influence of backward reflection on spatio-temporal instability of the fundamental mode in Yb3+-doped few-mode polarization maintaining fiber amplifiers with a core diameter of 10 µm was studied experimentally and theoretically. The mode instability threshold was registered to decrease dramatically in the presence of a backward reflection of the signal from the output fiber end; an increase of the signal bandwidth or input power resulted in the increase of the threshold. Numerical simulation revealed a self-consistent growth of the higher-order mode LP11 and a traveling index grating accompanying the population grating induced by the mode interference field (due to different polarizability of the excited and unexcited Yb3+ ions). The presence of the backward-propagating wave resulted in four-wave mixing on the common index grating induced by the interference field of pairs of the fundamental LP01 and LP11 modes.