Svetlana Alexandrovna Egorova

The aim of the study was to describe the experience in introduction, systematization and thematic analysis of the implemented programs of the Rospotrebnadzor for specialists of the Republic of Burundi (2023–2025) in the field of laboratory diagnostics, epidemiological monitoring and biosafety as part of the strategy to strengthen the biological sovereignty of African states. Materials and methods. The study is based on the analysis of reporting documents and educational materials from 15 advanced training courses and field exercises conducted for the staff of the National Institute of Public Health of Burundi (INSP) in 2023–2025. The training was delivered in English using adapted educational programs. Descriptive statistics and content analysis of course topics were employed. Results and discussion. During the reporting period, 16 educational events were conducted, over 130 specialists were trained. The programs covered such key areas as: general laboratory practice and biosafety (PBA of II–IV pathogenicity groups), molecular diagnostics (including third-generation sequencing on the MinION platform and LAMP), serological screening (ELISA diagnostics of natural-focal and hepatotropic infections), bacteriology of food-borne infections, zoological and entomological surveillance, as well as specific pathology (HIV infection, mpox). In October 2024, field exercises using a mobile laboratory for indication and monitoring of particularly dangerous infections (MLIM) were carried out. It is shown that systemic transfer of competencies, rather than one-time equipment supplies, forms the basis for autonomous response to biological threats. The implemented programs have confirmed the effectiveness of systematic approach to personnel training as a tool for strengthening the national laboratory network. The coverage of modern diagnostic methods meets the current needs of the republic. The developed educational modules have potential for duplication in other developing African countries.

Diphtheria is a serious infection, often characterized by a pronounced toxic component, which can be accompanied by severe complications of the cardiovascular and nervous systems. The primary method of infection prevention is immunization (primarily in children) with diphtheria toxoid, which induces effective and long-lasting antitoxic immunity. Objective of the study: evaluation of collective immunity to the causative agent of diphtheria among the population of several regions (Amur, Irkutsk, Nizhny Novgorod, Kaliningrad) and the Republic of Crimea. Materials and methods. The cross-sectional cohort randomized study involved 18,207 people uniformly stratified by age (1–5, 6–11, 12–17, 18–29, 30–39, 40–49, 50–59, 60–69, 70+ years), including: 3,576 in Amur; 3,657 in Irkutsk; 3,580 in Nizhny Novgorod; 3,613 in Kaliningrad regions; and 3,781 in the Republic of Crimea. All studies were conducted in strict accordance with the requirements of the Declaration of Helsinki. Immunoglobulin G Abs to the C. diphtheriae toxin were determined in the examined volunteers by enzyme immunoassay using a Russian-made test system. Data analysis and statistical processing were carried out using a web application. Results. The average cohort regional seroprevalence levels were: Amur Region - 82.3% (95% CI: 81.0 - 83.5); Irkutsk - 87.6% (95% CI: 87.6-88.9); Nizhny Novgorod - 86.5% (85.3-87.6); Kaliningrad - 74.2% (95% CI: 72.8 - 75.6); and the Republic of Crimea - 74.8% (95% CI: 73.4-76.1). In some cases, seropositivity did not reach 60%, namely: among individuals aged ≥60 in the Kaliningrad Region and the Republic of Crimea; and among individuals aged ≥70 in the Amur and Nizhny Novgorod Regions. Most volunteers had serum IgG Abs to diphtheria toxin at concentrations of 0.1–1.0 IU/ml, regardless of age, region, or vaccine type. Conclusion. The level of collective immunity mandated by current Russian documents (95% in children, 90% in adults) was practically not achieved in any region or age group (except children aged 1–5 years in the Irkutsk and Nizhny Novgorod Regions). In all regions, the least protected group were individuals aged 60 and older, among whom the seronegative value reached 30–45%.

The aim of the study was to assess the seroprevalence of hantaviruses, the causative agents of hemorrhagic fever with renal syndrome (HFRS), and their distribution to socio-demographic characteristics among the populations of Saint Petersburg and the Leningrad Region. A total of 4464 samples were analyzed, including 2265 samples from residents of Saint Petersburg and 2199 samples from residents of the Leningrad Region. Blood plasma samples were tested for specific immunoglobulin G (IgG) antibodies using enzyme-linked immunosorbent assay (ELISA). Blood samples were collected in 2023 from randomly selected volunteers. Hantavirus seroprevalence in Saint Petersburg was 5.39%, while in the Leningrad Region, it was 8.55%. In both regions, the highest proportion of seropositive individuals was found among volunteers aged ≥70 years, whereas the lowest seroprevalence was observed in the 1–17-year age group (inclusive). Seroprevalence was significantly higher in men than in women in both regions. The seroprevalence values identified in this study are comparable to those reported in similar studies in areas with a high incidence of HFRS. These findings may indicate that the true incidence of HFRS may be significantly higher than officially registered in Saint Petersburg and the Leningrad Region.

Introduction. Mass vaccination, implemented in Russia within the framework of the Russia National Vaccination Calendar, is a key component in the fight against vaccine-preventable infections (measles, mumps, rubella). The aim. The study’s aim was to assess herd immunity to the most common vaccine-preventable infections in several Russian regions. Materials and methods. The study involved 18 247 volunteers from several regions (Amur, Irkutsk, Nizhny Novgorod, Kaliningrad) and the Republic of Crimea. During the study, participants completed a questionnaire. A cohort of volunteers, stratified by age (1–5, 6–11, 12–17, 18–29, 30–39, 40–49, 50–59, 60–69, ≥ 70 years), was randomized using a web application. Antibodies to the measles, rubella, mumps were quantitated by ELISA (IgG) using Russian-made test systems. Results. The cohort average seropositivity magnitude for measles, mumps, and rubella were 75.7%, 84.0%, and 95.8%, respectively. For measles, the highest seropositivity level was observed in the group 1–11 years (Me = 74.8%; IQR = 68.5–83.5) and the group 60–70+ years (95.1%; IQR = = 93.2–95.8). Regarding mumps, these two ago groups also showed peak values: 1–11 years (Me = 85.9%; IQR = 81.4–92.5) and 60–70+ years (Me = 88.6%; IQR = 83.7–90.6). The lowest measles seroprevalence was observed in 18–39-year age group (Me = 59.7%; IQR = 55.9–64.6). For mumps, the lowest seroprevalence was also observed in 18–39-year age group (Me = 78.4%; IQR = 63.9–83.7). Regarding rubella, seropositivity was evenly distributed across the entire cohort: Me = 95.8% (IQR = 93.9–97.5). Among specific vaccines for immunization against measles/mumps or rubella, the mumps-measles or live monovalent rubella vaccine, respectively, was most or more frequently used. Conclusion. High measles and mumps seroprevalence among children is due to post-vaccination immunity following mass immunization, primarily with the mumps-measles vaccine. Seroprevalence in older adults is associated with childhood infections that have elicited post-infectious immunity. Rubella immunity was virtually independent of age, geographic location, or climate factors. Reduced measles and mumps seropositivity among middle-aged individuals may lead to emergence of sporadic cases of these diseases, which may require additional measures, including catch-up vaccination.

The hepatitis B (HBV), C (HCV), and D (HDV) viruses remain a major public health burden. Occult HBV infection (OBI) represents a hidden reservoir with clinical and epidemiological significance, yet its prevalence in Northwest Russia is unknown. We aimed to comprehensively assess the serological and molecular epidemiology of HBV, HCV, and HDV in St. Petersburg and the Leningrad region. Methods. In this cross-sectional study, 6773 apparently healthy volunteers were enrolled. Plasma samples were tested for hepatitis B surface antigen (HBsAg), antibodies to HBV core antigen (anti-HBc), antibodies to HBsAg (anti-HBs), antibodies to HCV (anti-HCV), and antibodies to HDV (anti-HDV) by ELISA. All anti-HCV- and anti-HDV-positive samples were tested for HCV RNA and HDV RNA by real-time PCR. All samples were tested for HBV DNA using a highly sensitive in-house nested real-time PCR assay (detection limit: 5 IU/mL). All “HBV DNA-positive, HBsAg-negative” cases confirmed by two independent extractions were classified as OBI. Vaccination status, self-reported history, and iatrogenic interventions were recorded. Results. Overall seroprevalence values were: HBsAg 1.7%; anti-HBc 11.3%; anti-HBs 43.0%; anti-HCV 1.9%; and anti-HDV 0.6%. Anti-HBc increased sharply with age (3.1% in children to 26.4% in the elderly, p < 0.0001), while anti-HBs declined (69.9% to 29.8%, p < 0.0001). HBV DNA was detected in 118 participants (1.7%). Of these, only 73 individuals (1.1%) were HBsAg-positive, while the remaining 45 participants (0.7%) had undetectable HBsAg, meeting the criteria for OBI. OBI was detected across all age groups, including children. Serological profiling of OBI cases revealed that 57.8% lacked both anti-HBc and anti-HBs, 35.6% had isolated anti-HBs, 2.2% had isolated anti-HBc, and 4.4% had both antibodies. HCV RNA was detected in 15.0% of anti-HCV-positive individuals (all adults). No HDV RNA was detected. Self-reported history underestimated true infection rates: 1.4% of those denying HBV infection were HBsAg-positive and 10.6% were anti-HBc-positive. Among those denying HCV infection, 1.4% were anti-HCV-positive. Vaccination coverage was 70.8%, declining from 90.9% in children to 39.0% in the elderly (p < 0.0001). Among vaccinated individuals, 48.0% lacked protective anti-HBs (<10.0 mIU/mL). Conclusions. This comprehensive serological and molecular study in Northwest Russia is the first to combine population-level serology with molecular detection of HBV, HCV, and HDV, including OBI in this region, and reveals that OBI accounts for a substantial proportion (38%) of all active HBV infections and is strongly associated with a history of iatrogenic interventions. The presence of OBI across all age groups, including children, shows that HBsAg screening alone substantially underestimates the true HBV burden. High rates of unrecognized infection and waning vaccine-induced immunity, highlight critical gaps in current surveillance. These findings provide an evidence-based rationale for integrating molecular testing into screening algorithms and for considering booster vaccination strategies to achieve viral hepatitis elimination goals.

Background: Hepatitis A (HA) and E (HE) represent a significant global health burden. Despite the development of effective vaccines against hepatitis A virus (HAV) and hepatitis E virus (HEV), outbreaks of acute HA and HE continue to occur worldwide. This study aimed to assess the seroprevalence of anti-HAV and anti-HEV IgG antibodies (Abs) in the population of Belgrade and to analyze their association with socio-demographic and clinical factors. Materials and Methods: A cross-sectional study was conducted on a sample of 2533 healthy volunteers in Serbia in May 2024. Participation was voluntary and web-based, leading to an overrepresentation of women and middle-aged adults, while children were underrepresented. Due to this non-probabilistic recruitment, the absolute seroprevalence estimates have limited generalizability to the entire population of Belgrade. Serum samples were tested for anti-HAV and anti-HEV IgG using commercial ELISA kits. The anti-HEV estimate is based on a single ELISA without confirmatory testing and should be interpreted with this limitation in mind. Statistical analysis included confidence interval estimation, chi-square tests, and Spearman’s correlation. Results: Overall seroprevalence was 20.5% (95% CI: 18.9–22.1) for anti-HAV and 22.6% (95% CI: 21.0–24.3) for anti-HEV. A strong, non-linear increase in anti-HAV seroprevalence with age was observed, rising sharply from 2.8% in the 18–29 group to 78.3% in those aged 70+. Anti-HEV seroprevalence also featured a significant positive correlation with age (rs = 0.99, p < 0.0001), increasing from 4.2% in children (1–17 years) to 49.2% in the 70+ group. Men had significantly higher anti-HAV seroprevalence than women (23.1% vs. 19.3%, p = 0.029). Individuals with a history of surgical interventions or blood transfusions had significantly higher odds of being anti-HEV positive (OR = 1.41, p = 0.0005). Vaccination coverage against HAV was low (1.8%), and Abs were detected in only 28.6% of vaccinated individuals. Conclusions: This study suggests high HEV seroprevalence and an age-polarized HAV seroprevalence in Serbia, indicating a significant shift in the epidemiological landscape while acknowledging the sampling and assay limitations stated above. The findings underscore a growing population susceptible to HAV and highlight the need for reinforced vaccination strategies, improved diagnostics, and targeted public health interventions.

Background/Objectives: The high prevalence of fluoroquinolone-resistant E. coli in healthy children represents a significant public-health risk, facilitating the spread of antimicrobial resistance and increasing the potential for difficult-to-treat extraintestinal infections with severe clinical outcomes. This study aimed to investigate the prevalence of fluoroquinolone resistance in multidrug-resistant E. coli isolated from presumptively healthy children in St. Petersburg, Russia, with a particular focus on fluoroquinolone resistance determinants. Methods: Phenotypic AST was performed on 307 E. coli isolates from fecal pediatric samples, comprising 230 isolates from 2012 to 2013 and 77 isolates from 2021 to 2022. A subset (n = 47) of MDR isolates underwent whole-genome sequencing. Results: The frequency of MDR E. coli strains rose significantly from 15.7% to 32.5% over the study period. The most significant increases in resistance among E. coli strains were to third-generation cephalosporins (CTX, CTZ) and fluoroquinolones (CIP), rising fourfold over a decade. Based on phenotypic resistance profiles of MDR E. coli to quinolones, the highest resistance rates were observed for MFX (80.9%) followed by NAL (74.5%), LVX (44.7%) and CIP (40.4%). Genotypic analysis revealed distinct pathways: low-level NAL resistance required only an S83 mutation in gyrA, whereas low-level MFX resistance was predominantly conferred by a plasmid-borne qnr gene. In contrast, resistance to CIP and LVX involved at least three QRDR mutations: S83L and D87N/Y in gyrA, and S80I in parC. Notably, our study showed the predominance of the ST131 and ST38 clones in E. coli isolated from pediatric samples. Conclusions: Our findings suggest that the efficacy of moxifloxacin for empirical treatment of infections caused by MDR E. coli might be severely compromised. Overall, the current study highlights that the pediatric gut microbiota serves as a reservoir for resistant E. coli with the expansion of multidrug-resistant clones independently of direct antibiotic selection pressure.

Introduction. Helicobacter pylori infection, however, data on the mechanisms of metronidazole (MTZ) and levofloxacin (LVX) resistance in Russia remain scarce. and levofloxacin (LVX) in Russia. The aim of the study is to identify the determinants of resistance in clinical isolates of H. pylori to MTZ and LVX using whole-genome sequencing data. Materials and methods. A retrospective analysis of 43 H. pylori isolates obtained from adult patients (2014–2022) was conducted. Susceptibility to antibiotics was determined using the bacteriological disk diffusion method. Whole-genome sequencing of 43 H. pylori strains was performed using a DNBSEQ-G50 sequencer. Results. The evaluation of the phenotypic drug susceptibility test results showed that 11 isolates were susceptible to MTZ (MTZ-S), 31 were susceptible to LVX (LVX-S), while 32 isolates were resistant to MTZ (MTZ-R), and 12 were resistant to LVX (LVX-R). To identify the association between phenotypic and genotypic resistance, an analysis of nucleotide substitutions in the gyrA, gyrB, rdxA, frxA, fdxB and fur genes was conducted. Of all the mutations identified in the gyrA and gyrB genes, only D91/GNY in the gyrA gene was associated with phenotypic resistance to LVX and was found in 4/12 (33.3%) of the isolates (p 0.05). The combined mutation D91G/N/Y+N87K in the gyrA gene was detected in 6/12 (50.0%) of LVX-R isolates (p 0.001). Point mutations in the rdxA gene were detected in 21.9% (7/32) of MTZ-R isolates, leading to a frameshift or premature termination of protein synthesis. None of the mutations in the frxA, fur and fdxB genes were associated with H. pylori resistance to MTZ. Conclusion. Based on the results of whole-genome sequencing of Russian clinical isolates of H. pylori, the detection of the combined mutation D91G/N/Y+N87K in the gyrA gene can serve as a predictor of the phenotypic resistance of H. pylori to levofloxacin.

Aim. This study aimed to assess the SARS-CoV-2 herd immunity in the Republic of Armenia (RA) by late 2022. Materials and Methods. A randomized study was conducted from 28 November to 2 December (2022) by the Saint Petersburg Pasteur Institute (Russia) in collaboration with the National Center for Disease Control and Prevention (Armenia). This study was approved by the ethics committees at both organizations. A volunteer cohort (N = 2974) was formed and grouped by participant age, region, or activity. Antibodies (Abs) to viral nucleocapsid antigen (Nc) and receptor-binding domain (RBD) in plasma were determined by ELISA. The statistical significance of differences was calculated using a p < 0.05 threshold, unless noted. Results. At the end of 2022, estimated SARS-CoV-2 seroprevalence (Nc and/or RBD Abs) among the Armenian population was 99% (95%CI: 98.5–99.3). It was evenly distributed throughout the cohort without any significant differences by age, region, or activity. Volunteers with low (32–124 BAU/mL) or medium (125–332 BAU/mL) anti-Nc Ab levels prevailed: 32.4% (95%CI: 30.7–34.1) and 25.5% (95% CI: 24.0–27.1), respectively. Regarding anti-RBD Abs, maximum levels (>450 BAU/mL) were detected in 40% of children. The share of individuals with high anti-RBD Abs levels increased with age, reaching 65% among those aged 70⁺ years. The important contribution to the formation of herd immunity to coronavirus infection was made by vaccination in the preceding period (1 April 2021 to 1 May 2022). The contribution from individuals with post-vaccination immunity was estimated to be above 80%. Hybrid immunity, formed after vaccination of those who had earlier experienced COVID-19, was characterized by greater effectiveness than post-vaccination immunity alone. Conclusions. Within the context of mass prophylactic vaccination, effective herd immunity to SARS-CoV-2 was formed, which helped to stop epidemic spread in the Republic.