МИКРОЭВОЛЮЦИЯ ВОЗБУДИТЕЛЯ ХОЛЕРЫ В СОВРЕМЕННЫЙ ПЕРИОД

Aim: To carry out comparative molecular genetic analysis of highly pathogenic atypical Vibrio cholerae strains biovar El Tor, isolated in the territory of RF, in order to determine micro-evolutionary alterations of cholera agent in the modern period. Materials and methods: 38 clinical strains have been examined by means of polymerase chain reaction, sequencing and MLVA-analysis. The selected strains were isolated at different periods of time during cholera epidemic complications and differed between each other in virulence. Results: It is demonstrated that new variants have emerged in the course of short-term microevolution. Their genome structure and function differ from those of all previously known strains. The genome alterations have been caused by point mutations in ctxB и tcpA genes associated with virulence and located in CTXφ prophage and pathogenicity island VPI-1 respectively, as well as by the extended deletion in pandemicity island VSP-II. Presented is the dynamics of genome structure and function alterations in modern strains. Conclusion: The discovered genomic alterations in the new variants of the agent evolved in the process of microevolution are indicative of their epidemic potential enhancement and probability of virulence potentiation.Цель исследования: провести сравнительный молекулярно-генетический анализ высокопатогенных атипичных штаммов Vibrio cholerae биовара Эль-Тор, выделенных на территории Российской Федерации, для выявления микроэволюционных изменений возбудителя холеры в современный период. Материалы и методы: исследовали 38 клинических штаммов методами полимеразной цепной реакции, секвенирования и MLVA-анализа. Выбранные штаммы были выделены в разные временные периоды эпидемических осложнений по холере и различались между собой уровнем вирулентности. Рeзультаты: показано, что в ходе непродолжительной микроэволюции возникли новые варианты, структура и функция генома которых отличается от всех известных ранее штаммов. Изменения генома были обусловлены точковыми мутациями в генах ctxB и tcpA, связанных с вирулентностью и входящих в состав профага CTXφ и острова патогенности VPI-1, соответственно, а также протяженной делецией острова пандемичности VSP-II. Представлена динамика изменений структуры и функции генома современных штаммов. Выводы: установленные геномные изменения у новых вариантов возбудителя, возникшие в процессе микроэволюции, указывают на возможность усиления их вирулентности и повышение эпидемического потенциала

Minimal operation current estimation for the temperature sensors based on p+-n GaP diode structures

A decrease of the operation current of diode temperature sensors (DTS) allows to considerably reduce the systematic measurement error of the sensors. In this connection we have made an estimation of the minimum operation current magnitude for p+-n GaP DTS. Thus there is an operation current I at which the total systematic error is minimal. This value I = Imin is taken as the desired current value

Minimal operation current estimation for the temperature sensors based on p+-n GaP diode structures

A decrease of the operation current of diode temperature sensors (DTS) allows to considerably reduce the systematic measurement error of the sensors. In this connection we have made an estimation of the minimum operation current magnitude for p+-n GaP DTS. Thus there is an operation current I at which the total systematic error is minimal. This value I = Imin is taken as the desired current value

Fragmentation and Multifragmentation of 10.6A GeV Gold Nuclei

We present the results of a study performed on the interactions of 10.6A GeV gold nuclei in nuclear emulsions. In a minimum bias sample of 1311 interac- tions, 5260 helium nuclei and 2622 heavy fragments were observed as Au projec- tile fragments. The experimental data are analyzed with particular emphasis of target separation interactions in emulsions and study of criticalexponents. Multiplicity distributions of the fast-moving projectile fragments are inves- tigated. Charged fragment moments, conditional moments as well as two and three -body asymmetries of the fast moving projectile particles are determined in terms of the total charge remaining bound in the multiply charged projectile fragments. Some differences in the average yields of helium nuclei and heavier fragments are observed, which may be attributed to a target effect. However, two and three-body asymmetries and conditional moments indicate that the breakup mechanism of the projectile seems to be independent of target mass. We looked for evidence of critical point observable in finite nuclei by study the resulting charged fragments distributions. We have obtained the values for the critical exponents gamma, beta and tau and compare our results with those at lower energy experiment (1.0A GeV data). The values suggest that a phase transition like behavior, is observed.Comment: latex, revtex, 28 pages, 12 figures, 3tables, submitted to Europysics Journal

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century