Journal of microbiology, epidemiology and immunobiology

Introduction. A sharp increase in the registered incidence of chronic hepatitis C, exceeding the average country level by more than 3 times, was noted in Omsk Region since 2023. The objective of the study was to answer the question of whether the observed increase in incidence is a consequence of the recent sharp increase in cases of hepatitis C virus (HCV) transmission, using molecular genetic analysis.

Materials and methods. Amplification of HCV core/E1 fragment and Bayesian phylogenetic analysis of corresponding nucleotide sequences were performed for serum samples from 344 patients with chronic hepatitis C diagnosed in 2022–2023, which accounted for 12.6% of all chronic hepatitis C cases diagnosed during this period in Omsk Region (n = 2730).

Results. Phylogenetic analysis demonstrated the presence of regional HCV clusters formed in 1990–2000s (95% HPD 1980–2014). The majority (86.0%, 295 out of 343) of HCV genotype 1a, 1b, 2a, 2c, 2k and 3a sequences isolated in 2023–2024 belong to different lineages circulating in the region for at least 10 years, which, together with the absence of large, homogeneous clusters with a recent tMRCA suggests the absence of a recent epidemiological link between these HCV cases. However, 12 (3.5%) sequences formed pairs with divergence in 2021–2023 (95% HPD 2018–2024), which indicates recent infection and suggests the presence of an epidemiological link between these cases of infection. Such pairs were identified for HCV genotypes 1a, 1b, 2a and 3a.

Conclusion. The observed upsurge in chronic hepatitis C incidence in Omsk Region apparently reflects the accumulated number of cases of HCV infection in the region resulted from transmissions occurred 10–20 or more years ago, and is a consequence of the increase in the HCV testing coverage. With an increase in the testing rates, especially in vulnerable groups where a significant number of undetected HCV infections are concentrated, an increase in the incidence of chronic hepatitis C can be expected in other regions of the country.

The aim of the study was to assess the frequency of mixed infections caused by several strains (mixed culture) of Mycobacterium tuberculosis among patients with HIV-associated generalized tuberculosis in St. Petersburg, and to conduct a comparative analysis of the genotypic diversity of strains in mixed cultures and among “pure” cultures of the tuberculosis pathogen.

Materials and methods. A total of 173 M. tuberculosis isolates obtained from autopsy specimens of 70 patients with HIV-associated generalized tuberculosis between 2012 and 2018 were analyzed. The Beijing genotype and its subtypes were determined using PCR and IS6110-RFLP typing. Non-Beijing isolates were spoligotyped, and their genetic families were identified using the international SITVIT2 database. Genotypic resistance to rifampicin and isoniazid was detected using the Amplitub-MDR-RV test system.

Results. Mixed infections were detected in 15 of 70 patients with HIV-associated multidrug-resistant tuberculosis. The same M. tuberculosis genotypes—Beijing, LAM, Ural, Haarlem, and X—were identified in the mixed cultures as in the pure cultures. Beijing strains, primarily subtypes B0/W148 (60%) and CAR (53.3%), were detected in all mixed cultures. The proportions of B0/W148 and LAM strains were significantly higher among mixed cultures (p <  0.05). Strains from mixed cultures had more than one mutation in different codons in the rpoB gene. Mixed cultures were more common in patients serving sentences in penal institutions (p = 0.0007).

Conclusions. The proportion of mixed infections among patients with HIV-associated tuberculosis was 21.4%; all mixed cultures contained strains of the Beijing genotype. A history of imprisonment was a significant risk factor for developing mixed infections.

Introduction. Peptidoglycans from lactic acid bacteria are a safe platform for surface display systems of heterologous proteins for medical purposes. The binding of target proteins to peptidoglycans can occur with the participation of the GW protein module.

Aim: to study the ability of GW module to bind proteins to peptidoglycan derived from lactic acid bacteria.

Materials and methods: The fused protein GW-RFP was obtained with the help of genetically engineering methods. The protein was isolated and purified. Lactic acid bacteria peptidoglycans were isolated and used in the binding reaction with the GW-RFP protein. To monitor the reaction progress, light and fluorescence microscopy and polyacrylamide gel electrophoresis electrophoresis (PAGE) were used.

Results: Methods for isolation and purification of peptidoglycans from Lactococcus lactis and Lactobacillus acidophilus have been developed. The recombinant GW-RFP protein consisting of the red fluorescent protein RFP and the GW module the AltA protein of Staphylococcus aureus has been cloned and expressed in Escherichia coli. It has been shown that the GW-RFP protein binds to the peptidoglycans from L. lactis and L. acidophilus in the amount of 24.9 ± 3.7 μg protein/100 μg (w/w) peptidoglycan from L. lactis and 21.3 ± 3.3 μg protein/100 μg (w/w) peptidoglycan from L. acidophilus. The GW-RFP protein can be removed from the peptidoglycans using a 0.5 M NaCl solution.

Conclusion: The GW module can be used for protein immobilization on the peptidoglycan from both lactococci and lactobacilli.

Introduction. In developing countries, yearly outbreaks of acute gastroenteritis records high rates of morbidity and mortality in children below five years.

Aim: present the whole genome sequence of Bacillus cereus BUKA implicated in acute childhood gastroenteritis.

Materials and methods. The sample was isolated from diarrheal stool of a child diagnosed with acute childhood gastroenteritis from a tertiary hospital in Nigeria.

Results. Antibiotics resistance profiling of the isolate revealed resistance to 79% (11/14) of the tested antibiotics including imipenem, penicillin, cefepime, ceftriaxone which suggests a strong ability to produce extended spectrum beta-lactamases, carbapenemases and cephalosporinases. Whole genome sequence insight confirmed the presence of chromosomally-encoded bla2 gene encoding enzyme that hydrolyze carbapenems, penicillin and cephalosporins. B. cereus encoding bla2 gene may be an emerging pathogen in the yearly incidence of acute childhood gastroenteritis in Nigeria.

Discussion. We herein report and implicate B. cereus harboring bla2 gene capable of hydrolyzing cephalosporins, and carbapenems as an emerging threat in acute childhood gastroenteritis in Nigeria

Introduction. Complement is a key humoral participant of immunity involved in defensive and pathological processes. Human lysozyme (hLZ), hen egg white lysozyme (HEWL) and lactoferrin (LF) are classical constituents of innate immunity. Complement and proteins of innate immunity are often co-localized but their interaction is poorly understood.

The aim of the work was to characterize functional interaction of LF and hLZ/HEWL with complement.

Materials and methods. Human blood serum was used as a source of complement. The complement classical and alternative pathway models contained antibody-sensitized sheep erythrocytes and rabbit erythrocytes respectively. The level of complement activation was estimated as serum hemolytic activity and anaphylatoxins production measured by ELISA. The bactericidal effect was estimated in colony-count assay. Permeabilization of outer and inner membranes of Escherichia coli ML-35p was evaluated with the use of chromogenic substrates of periplasmic and cytoplasmic enzymes. Enzymatic activity of lysozymes was measured in turbidimetric assay.

Results. We confirmed the data that LF selectively inhibits the classical pathway (IC₅₀ ~ 160 μg/mL; ~ 2 μM). We demonstrated for the first time that hLZ at high concentrations (40—160 μg/mL) moderately enhances the activity of the both complement pathways (C3 and C5 conversion as well as lytic activity) while HEWL at concentrations up to 160 μg/mL does not influence on complement activation. LF and hLZ modulated the classical pathway in an independent manner. LF did not prevent E. coli killing by serum but instead slightly increased bacterial viability in diluted serum. Lysozymes cooperated with complement in bacterial killing but LF partially prevented this in 5% serum. hLZ and HEWL accelerated bacterial inner membrane disruption regardless the presence of LF. The two enzymes accelerated the bactericidal effect of 50% serum, and hLZ did it slightly better than HEWL.

Conclusion. LF and hLZ produce opposing and independent effects on complement. We refine the idea of the interaction between complement and lysozyme and propose a new model in which hLZ cooperates with complement to accelerate bacterial killing via promotion of the classical and alternative pathways activation as well as synergism with membrane-attack complex. LF does not inhibit bacterial killing by serum but can oppose hLZ and complement synergism in diluted serum.

Introduction. The iron uptake system of Bacillus anthracis includes siderophores and hemophores, some of which are classified as additional virulence factors. The variability of the genes and proteins of this system in natural strains of the main genetic lineages of B. anthracis has not been studied previously, which determines the relevance of this study.

The aim is to characterize the variability of genes and proteins of the iron uptake system in natural strains of B. anthracis from different genetic lineages.

Materials and methods. The sequences of 947 B. anthracis genomes and 4 B. cereus biovar anthracis genomes taken for comparison were studied. In silico analysis was performed using the genome of the B. anthracis Ames Ancestor strain as a reference with the identification of polymorphisms in the BLASTn, BLASTp, and MEGA X programs.

Results. Variability was established for 23 of 25 and 14 of 18 siderophore and hemophore genes of B. anthracis, respectively. The frequencies of single nucleotide polymorphisms (SNPs), indels, and amino acid substitutions in strains of the main lineages A and B are comparable; in strains of lineage B, the non-ribosomal peptidyl transferase bacillibactin is inactive. In lineage C, the frequencies of polymorphisms are an order of magnitude higher. In B. cereus biovar anthracis, the frequencies are 1–2 orders of magnitude higher for indels and amino acid substitutions and 500 times higher for SNPs.

Conclusion. The variability of genes and proteins of the iron assimilation system is most pronounced in strains of B. anthracis lineage C. In strains of lineage B, with a comparable frequency of polymorphisms to lineage A, non-ribosomal peptide synthetase is inactive. These features may be associated with lower adaptive capabilities and lower prevalence of the main genetic lineages B and C compared to lineage A. The highest frequency of polymorphisms was observed in B. cereus biovar anthracis strains, which is explained by the special position of this subspecies.

The review presents current literature data on the main pathogenicity factors of Enterobacter spp., which ensure the colonization of various human ecological niches and the ability to develop an infectious process. The relevance of Enterobacter spp. is associated with their ability to cause nosocomial infections, especially in immunocompromised patients. The combination of pathogenicity factors provides the opportunity of shielding from the host body's defense mechanisms, which is necessary for the persistence of Enterobacter spp. The analysis of the literature data allowed us to determine the pathogenicity factors of Enterobacter spp., which make the greatest contribution to the development of the infectious process. The identification and study of key pathogenicity factors creates the basis for the development of new diagnostic methods and strategies for personalized therapy of Enterobacter spp. infections.

The purpose of the review is to summarize data on the pathogenicity factors of Enterobacter spp. and their role in the development of the infectious process in humans.

The analysis of literature data on the virulence factors of Enterobacteriaceae, particularly microorganisms of the Enterobacter spp., is conducted. The search and selection of literature were carried out using bibliographic databases, such as PubMed, Google Scholar, and the scientific electronic library Elibrary. The search queries included the following keywords, used individually or in various combinations: «Enterobacteriaceae», «Enterobacter spp.», «pathogenicity factors», «virulence factors», «persistence factors», «siderophores», «toxins», «adhesins», «capsule», «flagella», «Curli fibers», «secretion systems», «biofilm». In addition to keyword searches, the review included articles found through citation analysis within publications, as well as manually selected publications. This review includes articles published between 2002 and 2025.