The molecular mechanisms involved in the development of a high level of resistance to a wide range of antimicrobials in Burkholderia pseudomallei and closely related species have not been sufficiently investigated. In the present study, the properties of B. pseudomallei, B. mallei and B. thailandensis mutants with increased resistance to fluoroquinolones and cephalosporins were analysed. Resistance to pefloxacin, ofloxacin and ceftazidime in B. pseudomallei and B. thailandensis was accompanied by an increased resistance to aminoglycosides, beta-lactams, macrolides and chloramphenicol, whereas mutants of B. mallei were characterized by a narrower spectrum of resistance. With the use of the differential display technique, we demonstrated that multiple resistant variants of B. pseudomallei, B. mallei and B. thailandensis had an increased expression of putative efflux transporters belonging to the resistance-nodulation division superfamily and the major facilitator superfamily. With the application of PCR-single-stranded conformational polymorphism (PCR-SSCP) and sequencing, point mutations in gyrA quinolone-resistance determining region were detected in the part of multiple resistant B. pseudomallei and B. mallei mutants. These results indicate that various molecular mechanisms are involved in the development of multiple drug resistance in pathogenic Burkholderia and may be useful for further studying the adaptability of this microorganism and optimization of treatment.

Заболеваемость населения ЛЗН в 2015 г. на Северо-Американском континенте была следующей. В США, по данным Центра по контролю и предотвращению заболеваний США (Centers for Disease Control and Prevention, CDC, http://www.cdc.gov/), на 17.11.2015 г. зарегистрировано 1812 случаев ЛЗН, из них 65 % с нейроинвазивной формой инфекции (в 2014 г.-1935 случаев, из них 59,4 %-нейроинвазивная ЛЗН) [5]. В Канаде в сезон 2015 г., по данным Агентства общественного здравоохранения (Public Health Agency of Canada, PHAC, http://www. publichealth.gc.ca), выявлено 78 случаев ЛЗН (в сезон 2014 г.-21) [6].

The trend towards an increase in the West Nile fever incidence among the population in the Russian Federation, recorded in the season of 2018, continued and led to a significant increase in the incidence in 2019 (the indicator was 2 times higher than the long-term average). The features of manifestations of the epidemiological process of WNF in 2019 were identified: early registration of cases of the disease, activation of natural and natural-anthropourgic foci in the Southern Federal District (90 % of the total incidence in the Russian Federation), an increase in the share of neuro-invasive forms, dominance of patients aged 50 and older in the structure of the incidence, late epidemic season ending. It was established that in the season of 2019, the lineage 2 of WNV circulated in the European part of Russia. In the Volgograd Region, simultaneous presence of the West Nile virus and Sindbis virus in mosquitoes Culex pipiens and Culex modestus was identified. It was shown that the most significant factors for predicting the epidemiological situation on West Nile fever in the Volgograd Region are the average seasonal summer air temperature and monthly average indicators of relative humidity in the spring and summer periods, and the average monthly air temperatures in the spring and summer in the Rostov Region. In the Astrakhan Region, a significant correlation dependence of the influence of the considered factors on the incidence of the population has not been established. The forecast of the development of epidemic situation in 2020 does not exclude a possible increase in the incidence in the territories of the European part of Russia, endemic for West Nile fever, and the occurrence of local outbreaks in individual constituent entities, if the complex of climatic conditions and social factors favorable for West Nile virus coincide.

Burkholderia mallei and B. pseudomallei are highly pathogenic microorganisms for both humans and animals. Moreover, they are regarded as potential agents of bioterrorism. Thus, rapid and unequivocal detection and identification of these dangerous pathogens is critical. In the present study, we describe the use of an optimized protocol for the early diagnosis of experimental glanders and melioidosis and for the rapid differentiation and typing of Burkholderia strains. This experience with PCR-based identification methods indicates that single PCR targets (23S and 16S rRNA genes, 16S-23S intergenic region, fliC and type III secretion gene cluster) should be used with caution for identification of B. mallei and B. pseudomallei, and need to be used alongside molecular methods such as gene sequencing. Several molecular typing procedures have been used to identify genetically related B. pseudomallei and B. mallei isolates, including ribotyping, pulsed-field gel electrophoresis and multilocus sequence typing. However, these methods are time consuming and technically challenging for many laboratories. RAPD, variable amplicon typing scheme, Rep-PCR, BOX-PCR and multiple-locus variable-number tandem repeat analysis have been recommended by us for the rapid differentiation of B. mallei and B. pseudomallei strains.

During the epidemic season of 2012 453 cases of West Nile fever (WNF) were registered in the territory of the 21 constituent entities of the Russian Federation. Epidemic process is spreading itself towards the northern regions of Russia. The presence of markers of West Nile fever virus in carriers and vectors of the disease as well as acquired immunity among the population against the West Nile virus (WNV) have been identified in the territory of 53 constituent entities of the Russian Federation. The epidemic process is characterized by a number of peculiarities concerning both its epidemiological and clinical aspects. With the intensification of diagnostic works among the patients with clinical symptomatology similar to WNF, first and foremost in the territories where WNV markers have been detected, prognosticated is the registration of WNF incidence among the population extending over a large area of the Russian Federation.

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