The Role of Outer Membrane Vesicles of Agents of Particularly Dangerous Infections in the Pathogenesis and Immunogenesis of Infectious Process

The literature review is devoted to the modern concepts of the vesiculation phenomenon and its biological role in pathogenic bacteria – causative agents of particularly dangerous human infections. Data on the production, structure, composition, and functions of the outer membrane vesicles (OMV) of bacteria have been summarized. In recent years, the interest of researchers in the formation of spherical structures (so called bubbles or vesicles) from outer membrane of gram-negative bacteria has significantly increased. Such structures are surrounded by the double layer of a phospholipid membrane, the outer layer of which is enriched with lipopolysaccharide molecules. The inner space of vesicles could include various antigens, receptors, adhesins, toxins, enzymes, porins, etc. The formation of vesicles by the outer membranes of bacteria is recognized as a normal physiological manifestation of bacterial activity aimed at adaptation to environmental conditions. The investigation of the biological role of OMV showed their connection with the pathogenesis and immunogenesis of bacterial diseases. The review provides information on the peculiarity of induction, OMV composition and their participation in the processes of patho- and immunogenesis of severe infections caused by groups I–II PBA – the gram-negative causative agents of plague, tularemia, brucellosis, glanders, melioidosis, cholera, and formation of extracellular vesicles in a gram-positive anthrax pathogen. The particular attention is paid to the issue of developing safe and effective next-generation vaccine preparations based on bacterial vesicles

Comparative Molecular-Genetic Analysis of <i>Francisella tularensis</i> Strains Isolated in the Rostov Region in 2020 and Genome Sequences of the Strains Collected in Various Regions of the World

Six cultures of tularemia microbe from fallen and captured live animals were isolated during epizootiological monitoring in the steppe focus in the south-east of the Rostov Region in 2020 against the background of extensive epizootics in the populations of the common vole Microtus arvalis obscurus and the public vole Microtus socialis.The aim of the work was to develop an SNP-typing scheme and to conduct a comparative study of the phylogenetic relations between Francisella tularensis strains isolated in the Rostov Region (2020) and strains from other regions.Materials and methods. Genome-wide sequencing was performed on the MiSeq Illumina platform. The author’s software GeneExpert, PrimerM and VirtualPCR, written in the Java programming language, were used for the analysis.Results and discussion. The strains of tularemia agent, isolated on the territory of the Rostov Region in 2020, can be allocated to two different clusters. It is established that two strains of tularemia pathogen (F0884 and F0889) isolated in Turkey are genetically close to some isolates circulating in the Rostov Region. A unique INDEL marker characteristic of this group of strains has been identified. The comparison of our proposed typing scheme with the scheme of “canonical” SNPs has showed a fairly good consistency and convergence of results within large clusters, meanwhile using a set of 6626 SNPs allows for differentiating the strains within one canSNP type. It is revealed that the vaccine strain has a common canSNP type with clinical and natural strains. A set of SNP markers has been selected for comparative analysis. A new INDEL marker that enables intraspecific typing of F. tularensis has been discovered and the possibility of its application in vitro and in silico has been comfirmed

Comparative Analysis of the Pathogen Structure in Patients with Community-Acquired and Nosocomial Pneumonia in Medical Organizations of the Rostov, Tyumen Regions and Khabarovsk Territory at the Current Stage of a New Coronavirus Infection Pandemic

The aim of the study was to conduct a comparative analysis of the spectrum and antibiotic resistance of secondary pneumonia pathogens isolated in the territories of the Rostov, Tyumen Regions and Khabarovsk Territory against the background of a new coronavirus infection pandemic.Materials and methods. We investigated sputum samples from coronavirus-positive and coronavirus-negative patients with community-acquired pneumonia from medical organizations using bacteriological method, PCR mass spectrometry.Results and discussion. The study of the etiological structure of secondary pneumonia agents isolated from patients in medical organizations of the Southern, Ural and Far Eastern Federal Districts has revealed that the dominant cultures in SARS‑CoV‑2 “+” and SARS‑CoV‑2 “–” patients were yeast and yeast-like fungi. It has been found that under diversity of isolated fungi, Candida albicans species prevailed. The bacterial microflora is represented by a variety of gram-positive and gram-negative bacteria, of which Staphylococcus aureus and Klebsiella pneumoniaе were most often present in sputum. It has also been established that even before hospitalization of patients, community-acquired pneumonia could be caused by microorganisms of the ESKAPE group (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniaе, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter spp.), which are usually considered as polyantibiotic-resistant pathogens of nosocomial infections. Moreover, in coronavirus-positive patients with secondary community-acquired pneumonia, those pathogens were isolated 2–3 times more frequently than in coronavirus-negative ones. Assessment of sensitivity/resistance of isolated strains to antibacterial drugs has revealed a general trend: the majority of the strains, regardless of the type, were characterized by a narrow spectrum of sensitivity, having 3 or more markers of antibiotic resistance. This confirms the necessity and expediency of microbiological support of the patient during the entire infectious process. The most adequate drugs of choice, providing activity against 60–70 % of strains of the Enterobacteriaceae family, are amikacin and cefoperazone/sulbactam

Biological Properties and Genetic Characteristics of Francisella tularensis Strains Isolated in the Territory of the Rostov Region in 2020

Objective of the study was to investigate biological properties and genetic characteristics of tularemia agent strains isolated from natural foci of the Rostov Region in 2020.Materials and methods. Field material from natural foci of the Rostov Region was examined by serological, bacteriological, biological, and molecular-genetic methods. Cultural-morphological, biochemical, antigenic and pathogenic properties of isolated cultures were studied. Protein profles were obtained through MALDI-TOF MS using mass spectrometer Autoflex speed III Bruker Daltonics and Flex Control of Biotyper software. The genetic characteristics of the strains were determined by VNTR and INDEL typing and SNP analysis.Results and discussion. Six strains of tularemia pathogen were isolated from mouse-like rodents using biological method. The investigation of their biological features and data of PCR analysis and INDEL typing with canonical markers showed that all strains are typical representatives of the Francisella tularensis subsp. holarctica biovar EryR. VNTR typing by six genetic loci revealed that all strains belong to four individual genotypes. The strain isolated in 2020 in the Salsky district was identical to the strain which was isolated in the same area in 1989. Based on the whole genome sequencing of two strains, we established that they are closest to the cultures isolated in Turkey (2009, 2012) and Khanty-Mansiysk (2013) by the studied set of SNP markers. Thus, we found that both identical (or closely related) clones of the tularemia agent and new strains with unique genotypes which previously were not described for the Rostov Region can circulate in natural foci of this region for a long period of time

Features of Etiology of Community-Acquired Pneumonia Associated with COVID-19

Objective: comparative study of the etiological structure of community-acquired pneumonia in SARSCoV-2 “+”and SARS-CoV-2 “-“ patients who sought help from medical organizations in the Rostov Region.Materials and methods. Biological material from 508 patients diagnosed with community-acquired pneumonia who were on outpatient treatment or in hospitals in Rostov-on-Don was studied. Verification of respiratory viruses, including SARS-CoV-2 RNA, as well as M. pneumoniae, C. pneumoniae, and L. pneumophila was performed by polymerase chain reaction in nasopharyngeal smears. Bacteriological analysis of sputum was carried out using differential diagnostic media, identification of isolated pathogens was carried out using time-of-flight mass spectrometry on Autoflex (Bruker Daltonics) with BioTyper 3.0 software.Results and discussion. During the spread of a new coronavirus infection in the Rostov Region, the main etiological agent of community-acquired pneumonia is the new SARS-CoV-2 coronavirus. Specific character of pneumonia in patients with laboratory-confirmed COVID-19 is a higher incidence of mixed infection of both viral and bacterial etiology. Against the background of detection of a new coronavirus infection in patients with pneumonia, cases of detection of other types of coronaviruses have been registered (HKU-1,OC43, HL-63 and 229Е). The most common etiological agent of bacterial pneumonia in patients was Streptococcus spp., both in patients with COVID-19-associated pneumonia and in patients who tested negative for SARS-CoV-2. Coronavirus patients represent a high risk group for the development of mycotic lung lesions