Epidemiоlоgy and infectious diseases. Сurrent items

Objective. Determination of the epidemiological significance of the proportion of asymptomatic and mild forms in the dynamics of the incidence rate and structure of the novel coronavirus infection (COVID-19) globally and in the Russian Federation (RF) for 2020–2022.

Materials and methods. Data from the online resource Our World in Data was used to analyze COVID-19 incidence in populations across different countries. Information on the level and dynamics of incidence in the Russian Federation and the distribution of cases by severity were obtained by analyzing Rospotrebnadzor’s statistical form No. 1035, “Monitoring the number of cases of coronavirus infection, including community-acquired pneumonia, and fatalities,” for 2020–2022.

Results. The overall proportion of asymptomatic and mild forms of the disease in 2020–2022 ranged from 51.5% to 80.6%, averaging 64.2 ± 10.6%.

Conclusion. The high proportion of asymptomatic and mild forms of COVID-19 demonstrates the extreme epidemiological importance of timely diagnosis of such cases to prevent the spread of the pathogen.

Objective. Evaluation of the etiological structure of pathogens causing surgical site infections (SSIs), lower respiratory tract infections (LRTIs), and urinary tract infections (UTIs).

Materials and methods. Pathogen monitoring using specially developed data collection forms over a period of 7 years in 36 constituent entities of the Russian Federation was conducted. The coverage of etiologic deciphering of SSI, LRTI, and UTI cases over the entire observation period was 84.43% (95% CI 80.38–88.48).

Results. The leading pathogens for UTI were K. pneumoniae (25.71%, 95% CI 22.69–28.72), E. coli (18.95%, 95% CI 16.01–21.89), and Enterococcus spp. (16.19%, 95% CI 13.68–18.69). In the etiology of LRTI, the most significant were: K. pneumoniae – 19.77% (95% CI 17.43–22.11), the group “other microorganisms” – 14.96% (95% CI 6.14–23.78), the group “other gram-positive microorganisms” – 11.37% (95% CI 9.43–13.31). The predominant etiologic pathogens in SSIs over the 7-year period were: S. aureus – 20.56% (95% CI 19.91–21.21), E. coli – 17.3% (95% CI 16.41–18.20), K. pneumoniae – 12.37% (95% CI 11.68–13.07), and S. epidermidis – 10.23% (95% CI 9.66–10.79).

Conclusion. The etiologic pathogens in HAIs remained stable over the observation period, but regional differences were observed when comparing the results with data from other studies.

Since the start of vaccination of the population of our country against hepatitis B, a downward trend in the incidence of the acute form, from 47.3 cases per 100,000 in 1999 to 0.32 cases per 100,000 by 2024 has been observed. Registration of chronic hepatitis B, which began in 1999, shows a 1.7-fold decrease from the peak (16 in 2001) to 9.45 in 2024 between 1999 and 2024. An analysis of the results of studies on the hepatitis B epidemic process before and after the start of vaccination, published in domestic and international literature, has shown that studying population and individual immunity through serological monitoring, with a focus on the causes of non-response to vaccination and revaccination at the molecular genetic level, remains relevant for predicting an adequate immune cellular response. Risks of infection persist due to insufficient diagnostic coverage of risk groups, such as migrants, and the lack of registration of latent forms of infection.

Objective. Evaluation of the composition of the sputum microbiome in patients with pneumococcal pneumonia depending on the prevalence of metabolic syndrome components.

Materials and methods. A total of 38 patients with pneumococcal pneumonia were examined, stratified into three groups according to the International Diabetes Federation (IDF) metabolic syndrome criteria: Group A (n = 17): abdominal obesity + type 2 diabetes mellitus + arterial hypertension + hypertriglyceridemia; Group B (n = 12): abdominal obesity + type 2 diabetes mellitus + low high-density lipoprotein levels; Group C (n = 9): abdominal obesity + arterial hypertension + hypertriglyceridemia. Streptococcus pneumoniae was identified by culture and MALDI-TOF MS; taxonomic analysis was performed by 16S rRNA sequencing.

Results. The highest bacterial load of S. pneumoniae and the slowest elimination during therapy were observed in Group A (7.2 × 10⁶ CFU/ml) and Group B (5.8 × 10⁶ CFU/ml). The microbiota of patients in Groups A and B was characterized by pronounced dysbiosis with a predominance of Streptococcus (49.1 ± 2.4%) and a combined increase in opportunistic pathogens (Haemophilus, Klebsiella), while in Group C, commensal taxa (Prevotella, Veillonella) predominated. The dysbiosis index was highest in Group A (3,8 ± 0.3) and lowest in Group C (0,6 ± 0,1) (p < 0.001).

Conclusion. Severe respiratory dysbiosis was recorded in patients with metabolic syndrome, an essential component of which was type 2 diabetes mellitus.

Objective. Assessment of the number and ratio of CD4⁺ and CD8⁺ lymphocytes in lungs affected by focal tuberculosis.

Materials and methods. The study was performed on autopsy lung material from 40 deceased men aged 30–55 years with focal tuberculosis diagnosed during their lifetime. Immunohistochemical methods were used to assess the immune response.

Results. When studying the expression localization of the studied markers in the lungs in the «conditionally healthy» group, the majority of CD4⁺ and CD8⁺ lymphocytes were determined predominantly in the interstitial space, with single ones near blood vessels and in the lamina propria of the bronchial mucosa. In focal tuberculosis, the highest number of CD4⁺ lymphocytes was found in the granulation tissue (12.2 ± 1.9 in the field of view) surrounding the caseous necrosis focus. In areas without signs of inflammation, the number of cells decreased (4.2±1.3 in the field of view). CD8⁺ lymphocytes predominated over CD4⁺ lymphocytes both in the area around the necrosis (48.8 ± 5.8 in the field of view) and in distant areas (12.3 ± 0.3 in the field of view). The immunoregulatory index (CD4⁺/CD8⁺) in the tuberculous lesion and in the area without signs of specific inflammation was 0.25 and 0.34, respectively, indicating suppression of local cellular immunity.

Conclusion. In focal tuberculosis, the balance between T-helper (CD4⁺) and T-suppressor (CD8⁺) cells is disrupted in the area of specific inflammation. The identified quantitative changes and decrease in the immunoregulatory index in the studied areas can serve as objective criteria for the development of local immunodeficiency and can be considered markers for refining the prognosis of the disease course and choosing immunocorrection tactics.

Objective. Assessment of the antimicrobial resistance profile of Salmonella isolates recovered from food products in the Russian Federation from 2018 to 2024 using phenotypic analysis and identification of genetic determinants of antibiotic resistance.

Materials and methods. From 2018 to 2024, 3,843 non-typhoidal Salmonella enterica subsp. enterica isolates obtained from food products in Russia were analyzed. Generic identification was performed using MALDI-TOF mass spectrometry. Serotyping was performed by agglutination testing using domestically produced Salmonella sera (PETSAL, Russia) according to the Kauffman-White scheme. Phenotypic susceptibility was determined by the broth dilution method (BD) on a Vitek 2 Compact analyzer. Antibiotic resistance genes were identified in multidrug-resistant (MDR) isolates using whole-genome sequencing (WGS).

Results. Salmonella was most frequently isolated from poultry (55.8%), cooked foods (27.5%), and meat products (14.2%); less than 1% of isolates were obtained from confectionery, fish, and dairy products. Phenotypic resistance was recorded to cephalosporins (18.1%), fluoroquinolones (60.1%), aminoglycosides (18.1%), tetracyclines (36.7%), chloramphenicol (27.0%), trimethoprim (66.1%), nitrofurantoin (59.1%), trimethoprim-sulfamethoxazole (21.9%), and carbapenems (0.1%). WGS was used to analyze 31.2% of the sample. The most prevalent sequence types were ST32 (S. Infantis), ST11 (S. Enteritidis), ST198 (S. Kentucky), and ST34 (S. Typhimurium). The genomes were found to harbor resistance determinants to aminoglycosides (93.0%), β-lactams (46.4%), quinolones (31.0%), tetracyclines (97.4%), sulfonamides (89.6%), trimethoprim (59.8%), phenicols (41.1%), macrolides (57.9%), and (less frequently, 1%) lincosamides, colistin, and rifampicin.

Conclusion. Poultry production is the primary reservoir for Salmonella, with circulating isolates demonstrating high levels of resistance to clinically significant antibiotics, primarily fluoroquinolones and trimethoprim. The prevalence of epidemiologically significant clones (ST32, ST11, ST198, ST34) highlights the need for enhanced control at all stages of the food chain and continued molecular genetic monitoring to track the spread of resistant clones.

Objective. Determination of the risk criteria for healthcare-associated infections (HAI) in healthcare facilities (HF) of Rostov-on-Don and the Rostov Region.

Materials and methods. From 2012 to 2024, 2,709 cultures of non-fermenting gram-negative bacteria (NFGNB) were isolated from healthcare facilities. Their species, antibiotic sensitivity, and biofilm-forming capacity were studied. Bacteriological studies and antibiotic susceptibility testing were conducted using the disk diffusion method. Biofilm formation of NFGNB was assessed using the authors’ method. To identify loci of antibiotic resistance, 13 randomly selected Pseudomonas aeruginosa strains isolated from various sources were analyzed.

Results. The detection rate of NFGNB in city hospitals ranged from 5% to 28%. The most frequently detected bacteria were Pseudomonas aeruginosae, Stenotrophomonas maltophilia, and Acinetobacter baumannii. A high, stable incidence and prevalence of pan-antibiotic-resistant NFGNB, along with increasing antibiotic resistance and biofilm formation potential, were noted. A pilot study of Pseudomonas antibiotic resistance loci showed that the number of identified clinically significant R-AB genes in Pseudomonas can be arranged in descending order: tetO > aadA2 > blaVIM > ermB > vanA > sul2.

Conclusion. The identification of dominant potentially dangerous microbial cultures, the presence of strains resistant to multiple antibiotic groups among isolates, and lack of susceptibility to disinfectants should be considered criteria for the risk of developing HAIs in medical institutions. Monitoring the antibiotic resistance of NFGNB strains can allow for adjustments to antibacterial prescribing regimens in medical institutions, assess the risk of developing HAIs, and develop appropriate anti-epidemic measures.

The COVID-19 pandemic was accompanied not only by the development of acute respiratory pathology but also by an increase in the incidence of delayed cardiovascular complications, indicating the presence of complex pathogenetic interactions in the virus-host system. The multisystem nature of the disease, driven by several key mechanisms, has now been established. The first is related to the virus’s tropism for tissues expressing the angiotensin-converting enzyme 2 receptor, leading to an imbalance in the renin-angiotensin system (RAAS) with predominant proinflammatory, vasoconstrictor, and prothrombotic effects. The second is the ability of SARS-CoV-2, which has a tropism for cardiac tissue, to initiate a signaling cascade of cardiomyocyte necroptosis. The third mechanism is mediated by virus-induced hypomethylation of the promoter regions of genes encoding proinflammatory cytokines, which contributes to the development of chronic systemic inflammation and damage to the vascular endothelium.

Conclusion. To identify the leading pathogenetic mechanism, promptly predict the risk of cardiovascular complications, and determine patient management strategies, it is necessary to develop and implement a strategy for the qualitative and quantitative assessment of specific biological markers into clinical practice. Their implementation will reduce disability and mortality rates among individuals who have recovered from COVID-19.