REVIEWS
ORIGINAL ARTICLES
Objective of the study is to evaluate the serological activity of rabies virus antigens isolated from the brain tissue of mice by homogenization on FastPrep followed by ultracentrifugation. Materials and methods. Producer strain of the rabies virus “Ovechiy” GNKI. The rabies virus was isolated from the brain tissue of experimentally infected mice, followed by the study of the electrophoretic profile. The serological activity of the virus components was assessed by immunoblot and ELISA using specific anti-rabies sera.
Results and conclusions. In the course of comparing the methods of isolation and purification of the rabies virus antigen, it was found that most optimal one is to use a homogenization on FastPrep-24, followed by fractionation in a sucrose gradient. As a result of fractionation in a graded sucrose density gradient with a concentration of 15–50 % at 25000 g for 120 min, five fractions of the rabies virus components were obtained. The maximum purified protein fraction was from 15–20 % sucrose zone, which corresponded to a molecular weight of 67 kDa. The specific antigen activity of the fraction in ELISA reached up the titers of 1:1280 (Specificity coefficient 2.2).
Using immunoblot of antigens, obtained from the sucrose gradient in the range of 40–45 % and 20–35 % after ultracentrifugation, one major fraction of polypeptides (54 kDa) was detected, which showed the highest antigenic activity. The results obtained will be useful in the design of test systems for rabies screening and monitoring the effectiveness of anti-epizootic measures.
Spatial indicators of epizooties in natural plague foci are used for justified planning and carrying out measures on epidemiological welfare provision for the population residing in enzootic territories. Plague affected regions are identified by real geographical coordinates of epizootic sites. Objective of the study is to develop numerical methods for determination of boundaries and area of epizootic regions according to the results of epizootiological monitoring. Materials and methods. Utilized are the digital maps of the natural plague foci, the data on epizootic points, and computer software. Results and conclusions. Buffer zones in the form of circumference of 5 km radius were established around each epizootic point with the help of computer application “ArcGIS 10.x” as a counterpart of circular extrapolation method. Resultant epizootic region over a certain season was generated by several overlapping circumferences.
Evaluated were the area and extension of the region, as well as the presence of epidemiologically significant objects within its bonds.
Actual positioning of the region, visualized on the focus map, is used for specified task assignment as regards carrying out of various preventive measures in this or that part of the area.
Objective of the study is to assess the effectiveness of anti-mosquito measures (against Aedes aegypti and Aedes albopiсtus mosquitoes) in the territory of Sochi and determine the ways to improve the tactics of insecticide, including larvicide, treatments.
Materials and methods. The monitoring data were analyzed in 156 points of mosquito numbers counting, 57 of which were located at sites that were subjected to treatment, including repeated ones. The count of mosquitoes was carried out by the “observer” method within 20 minutes. Statistical processing of the data was carried out using the “Past” package. Differences in mean values were calculated using the Mann-Wilcoxon-Whitney test. At the points of detection of Ae. aegypti or Ae. albopictus mosquitoes additional targeted anti-mosquito treatments were carried out. Results and conclusions. In 2016, an extremely low numbers of mosquitoes Ae. aegypti were observed. Abundance of mosquitoes Ae. albopictus is described as “high”: more than 11,000 specimens were collected in the territory stretching from the state border with the Republic of Abkhazia in the east to the city of Novorossiysk, inclusive, to the west.
The highest numbers of mosquitoes Ae. albopictus were registered in the territory of cemeteries. Performed anti-mosquito activities demonstrated their effectiveness in urbanized areas and some park zones with a high numbers of permanently residing population and tourists due to higher treatment density, small number of places favorable for the breeding of mosquitoes Ae. albopictus directly in these territories and nearby. To prevent the spread of mosquitoes Ae. aegypti and Ae. albopictus in the territory of epidemically significant objects from neighboring sites, monitoring of their numbers should be continued throughout the city and in all potential habitats. The continuation of monitoring activities across the entire Black Sea coast remains a topical issue due to the possibility of further expansion of the mosquitoes areal.
Objective is to study the role of small mammals, habitant in the Republic of Guinea, in Lyssavirus circulation. Materials and methods. Investigations were conducted using RT-PCR; nucleotide sequence of Lyssavirus cDNA fragments was identified with the help of sequencing with further phylogenetic analysis. Results and conclusions. Tested have been 356 brain samples from small mammals for the presence of Lyssavirus RNA using RT-PCR with genus-specific primers. The animals were caught in the suburbs of Kindia city in 2016. The samples were obtained from wild animals pertaining to Rodentia, Chiroptera, Eulipotyphla, and Carnivora orders.
Lyssavirus RNA was detected in 31 samples (8.7 %). For 14 PCR positive samples the appurtenance to Lyssavirus was confirmed through identification and analysis of nucleotide sequences of the collected short cDAN fragments of viral genome. The presence of rabies virus RNA in positive tests was excluded from PCR with the help of species specific primers. The pool of samples from black rats, Rattus rattus, positive for Lyssavirus RNA, contained RNA characteristic of Mokola lyssavirus species. Specified has been nucleotide sequence of matrix protein M gene fragment of Mokola virus. Genetic material of Mokola virus was detected in the Republic of Guinea for the first time ever.
Objective of the study is to conduct epidemiological analysis of official statistical data on brucellosis morbidity rates over the period of 2005–2014 in different constituent entities of the Russian Federation, using Wald method. Materials and methods. Utilized were recording and reporting documents of the Federal Service for Surveillance in the Sphere of Consumers Rights Protection and Human Welfare, FBHI “Federal Center of Hygiene and Epidemiology” of the Rospotrebnadzor, and WHO information resources.
Results and conclusions. Studies of peculiarities of epidemic process development over the long-term period have allowed for identification of entities that are the most affected by the diseases. The results obtained on the morbidity rates in the Russian Federation over the period of 2005–2014 testify to the fact that first comes North Caucasian Federal District (NCFD) (62 %), next go Siberian (SbFD) (16 %) and Southern (SFD) (13 %) Federal Districts, second and third lines of the list respectively. Other regions account for 9 % of the load. The largest share of morbidity in NCFD entities belongs to the Republic of Dagestan – 62 %. Thereat, annual increment rate is 5.54 cases, which points to stabilization and some downward trend. Application of this morbidity rate prediction tool provides for in-time planning of clinical-diagnostic, prophylactic, and anti-epidemic measures in brucellosis foci. Wald method for forecasting of morbidity can be used for other infectious diseases too.
Objective. Comparative study of the protein profiles of typical virulent strains and their isogenic avirulent LPS-defective mutants of Francisella tularensis using mass spectrometric analysis. Materials and methods. Six typical virulent strains of F. tularensis of three main subspecies and eight isogenic avirulent variants which have different lesions in LPS structure were used in this investigation.
Protein spectra were obtained by MALDI-TOF MS using mass spectrometer Autoflex speed III Bruker Daltonics and Flex Control software of Biotyper. Earlier we expanded the database by introduction of the mass spectra of 40 typical F. tularensis strains of the three main subspecies. Results and conclusions. It was shown that the high quality spectrograms were obtained by means of the extraction of bacteria with ethanol supplemented with formic acid, as compared with two other methods (extraction matrix or TFA).
According to the data received, the typical virulent strains of tularemia agent of the three main subspecies have significant differences in the major peaks of protein profiles. This suggests that MALDI-TOF MS can be used for the subspecies differentiation of F. tularensis.
However, a comparative study of the protein spectra of virulent and isogenic avirulent F. tularensis strains of the same subspecies did not detect any essential differences. We were able to identify only two individual peaks (m/z 4673, 6929) which were characteristic of all virulent strains and one peak (m/z 7256) – of all avirulent strains. Thus, MALDI-TOF MS allows for reliable determination of the subspecies affiliation of F. tularensis strains but does not allow for evaluation of the strains` virulence. The results indicate that MALDI-TOF MS is a useful method for identification of typical and antigen-modified LPS-defective F. tularensis strains.
BRIEF COMMUNICATIONS
Objective of the work was to compare the results of monitoring of Vibrio cholerae strains isolated in the territories of federal districts, their constituent entities and from certain water bodies between 2006–2016. Based on the methodology, using updated geoinformation system “Cholera 1989–2014”, a comparative study of the dynamics of isolation and biological properties of 586 Vibrio cholerae O1, O139 strains and R-variants, collected from the surface water bodies in the administrative territories of Russia, was carried out. Eventually it is established that Vibrio cholerae strains of various serogroups are found in the territory of all federal districts, but not in all the entities included in them. It is shown that the greatest number of isolated strains was registered in the Southern Federal District. The overwhelming number of Vibrio cholerae strains, isolated in the country, were non-toxigenic. It was noted that against the background of epidemiological welfare, the detection of single epidemiologically significant strains continued (Rostov Region).
ctxA–tcpA+ strains were found in the Southern, Far Eastern and North-Western Federal Districts. It is established that until 2013 in five constituent entities strains of Vibrio cholerae O1 and O139 in water bodies were not detected. Non-toxigenic strains of Vibrio cholerae O1 El Tor Ogawa serovar prevailed in the territories of the Southern and Ural, and Inaba serovar – in the remaining Federal Districts.
The most frequently isolated were non-toxigenic Vibrio cholerae O1 strains with phagotype 15, while isolates with phagotypes 4, 5, 10, 14 and 17 were traced only in the Southern Federal District. The data obtained formed the basis of the approach that contributes to a comprehensive assessment of the epidemiological situation on cholera in the territory of Russia and highlighted the prospects for using GIS to improve the effectiveness of cholera vibrio monitoring in surface water bodies.
INFORMATION
ISSN 2658-719X (Online)