Vol 97, No 3 (2020)

The Central Research Institute of Epidemiology of Rospotrebnadzor presents priority data obtained from the largescale population PCR-based study of the changes in the rates of circulation of SARS-CoV-2 among relatively healthy residents of Moscow and Moscow Region.

Rationale. The novel coronavirus infection caused by SARS-CoV-2 (COVID-19) continues to spread worldwide, though the epidemiological situation varies across countries. It is of interest to estimate the pediatric incidence in a separate constituent entity of the Russian Federation, Moscow Region (MR) closely connected with Moscow (accounting for the highest number of COVID-19 cases in Russia). Assessment of the epidemiological data is interesting due to the late onset of the epidemic outbreak, the preventive lockdown imposed during the early stages, and extensive testing of all the identified contacts.

Purpose of the study: Assessment of the pediatric incidence of COVID-19, including identification of its main clinical and epidemiological characteristics, based on the monitoring data for the current situation in MR.

Materials and methods. A retrospective analysis of all pediatric cases of laboratory-confirmed COVID-19 in MR (1,047 children of all ages) was performed. The time span covered the data of the daily monitoring of the epidemiological situation from the beginning of reporting (53 days in total). The information was obtained from the database of the Rospotrebnadzor Territorial Administration of MR and collected in compliance with the regulations on Daily Monitoring of Children with Coronavirus Infection, Management Section, State Information System, MR.

Results. The pediatric cases of COVID-19 accounted for 6.3% (95% CI2 5.9–6.7) of all the cases reported by 6/5/2020 (16,590); the total infection rate of the pediatric population in the region was 0.07% (0.06–0.09). The basic reproduction number ranged from 4.8 (during the two-week exponential growth phase) to 2.7 (during the later period characterized by a slowdown in the incidence rate) and averaged 3.8 (3.0–4.57). The clustering rate of COVID-19 among children was high, reaching 82.8% (79.7–85.6) with a small average number of cases detected in the cluster — 1.21 (1.16–1.26). Asymptomatic COVID-19 cases prevailed significantly, amounting to 62.2% (59.2–65.1), including 73.1% in newborns; severe cases accounted for 0.38% (0.35–0.41) and hospitalized cases totaled 12.0 (10.1–14.2). No death cases were reported. The mean age of the diseased and infected was 8 [4; 13] years old. Boys prevailed insignificantly (53.2%).

Conclusion. There is a distinct stage-by-stage development of the epidemic situation among children in MR. In the pediatric population, COVID-19 was generally acquired from a secondary household transmission within family clusters. Early preventive measures and extensive testing helped to reduce the period of exponential growth and, therefore, to avoid large clusters of infection. In addition, 17.2% of the COVID-19 clusters were identified as those where the child was the first to become sick. In the future, it is necessary to practice distancing and provide effective isolation of diseased children and adults, since the high rate of incidence in children can lag behind the incidence rate in adults.

Introduction. In a number of countries, including Russia, there is no systematic registration and reporting of parvovirus infection cases; the extent of its spread can be estimated by using humoral immunity rates.

Purpose of the study: Assessment of seroprevalence of parvovirus B19 (B19V) in different age groups of population of Russia, Central Asia, and West Africa.

Materials and methods. A total of 1,732 blood serum samples from residents of St. Petersburg and Nur-Sultan, migrant workers from Uzbekistan and Tajikistan, residents of the Republic of Guinea were studied for IgG antibodies to B19V.

Results. The highest seroprevalence rates were identified in St. Petersburg and Nur-Sultan (62–65%); the lowest rates were registered among migrant workers from Uzbekistan and Tajikistan (47%). The results for the Republic of Guinea showed a B19V seroprevalence rate of 53%. It was found that there is an increasing trend of seropositivity with age; the percentage of seropositive individuals clearly increases in older age groups: up to 55% — among migrant workers from Central Asia and residents of the Republic of Guinea; up to 80–85% — among residents of St. Petersburg and Nur-Sultan.

Discussion. The obtained results confirm the worldwide occurrence of parvovirus infection. People susceptible to infection can cause infection spreading in high-risk groups — among pregnant women, immunodeficient patients, blood product recipients, and cancer patients.

Objective. To designate the nasopharyngeal carriage of bacterial pathogens among children and adults diagnosed with recurrent respiratory diseases residing in the Khabarovsk city during a four-year period.

Materials and methods. Nasopharyngeal and oral swabs obtained from 7,043 children and adults were tested using classical bacteriological methods. In order to grow “difficult-to-culture” microorganisms a columbian agar with addition of 5% defibrinated sheep blood, incubation in the atmosphere rich with CO₂ (5%), bacteriological analyzer Vitek 2 Compact were used. Real-time PCR was used to confirm the identification of S. pyogenes.

Results. A high level of nasopharyngeal pathogens carriage (47%) was detected. The most prevalent microorganisms were as follows: S. pneumoniae (47%), M. catarrhalis (30.4%), H. influenzaе (17.5%), S. pyogenes (5.2%). The age groups at risk were children aged 0–6 years for S. pneumoniae and children aged 7–12 years for S. pyogenes. An emerging trend it the level of nasopharyngeal carriage of S. pneumoniae observed in 2018 was followed by the increase of registered incidence of pneumococcal pneumonia.

Conclusion. Nasopharyngeal carriage of S. pneumoniae imposes a high risk of community-acquired pneumonia and other pneumococci-associated diseases, predominantly in children.

Aim. Detection of SXT elements in cholera vibrios O1 and nonO1/nonO139 serogroups and study of the effectiveness of their conjugative transmission to Escherichia coli cells.

Materials and methods. In conjugation experiments, Vibrio cholerae O1 El Tor (3) and V. cholerae nonO1/ nonO139 (3) strains were used as donors. Donor strains, recipients, and transconjugants were tested in realtime PCR for sensitivity to antibiotics and for the presence of drug resistance genes and integrase gene (int). Electrophoresis was carried out on a 0.7% agarose gel with ethidium bromide staining.

Results. Resistance to chloramphenicol, trimethoprim/sulfamethoxazole, streptomycin was transmitted in conjugation experiments with a frequency of 2.1 × 10^–9–7.1 × 10^–9. The genes int and dfrA1 (resistance to trimethoprim/sulfamethoxazole) were found in most V. cholerae strains, and were stably transmitted to E. coli QD Rif ^r cells and in reverse crosses of V. cholerae O1 El Tor 5879 Nal^r .

Conclusion. The detection of the SXT element in V. cholerae strains and its successful horizontal transfer emphasize the need to detect such mobile genetic elements to control the spread of antibiotic resistance in V. cholerae.

A significant mortality rate from infectious diseases is largely mediated by the widespread and uncontrolled use of antibiotics, which has led to the emergence of drug-resistant strains of bacteria. The rapid evolution of bacterial resistance to antimicrobials is a serious challenge for modern health care, mediates the need to create new antibiotic agents, as well as to intensify the study of molecular mechanisms underlying the formation of microorganism resistance. One of these mechanisms is bacterial persistence, manifested by the formation of persistent cells in the culture, which are a phenotypic variant of the isogenic population. The persistence of bacteria can occur spontaneously, regardless of exposure to antimicrobials or environmental reasons, such as lack of nutrients, oxidative stress or hypoxia. This small cell subpopulation is able to maintain viability even in the presence of antimicrobial agents at concentrations many times higher than therapeutic. The presence of persistent cells of pathogenic bacteria in the host organism reduces the effectiveness of antibiotic treatment, not due to the genotypic drug resistance of the microorganism, but due to the presence of phenotypic resistance of persister cells. The difference is fundamental, since cell-persisters are insensitive to any antibiotics and the development of fundamentally new antimicrobial strategies is necessary for their eradication. Persister cells are phenotypic variants of the maternal culture of bacteria that are present in all populations of microorganisms, and after the onset of favorable conditions, they are able to reclaim and form a new generation of vegetative bacteria. This review discusses modern concepts of the molecular genetic mechanisms of bacterial persistence with an emphasis on their clinical significance for the occurrence of persistent infections, and discusses innovative technologies for the eradication of resistant cell forms of microorganisms.

Review of the book by Academician F.I. Ershov «History of Virology by D.I. Ivanovsky to the Present Day».

To the 95th anniversary of Professor Kostyukova Natalia Nikolaevna: 73 years of service to science.

In memory of Valentina Borisovna Gervazieva.