Retrospective analysis of dissemination of the 2.MED1 phylogenetic branch of Yersinia pestis in the Caucasus.

The 2.MED1 phylogenetic branch of Yersinia pestis of the medieval biovar became widespread in the Caspian Sea region, the Caucasus, and the Northern Aral Sea region in the 20th century, causing outbreaks and epizootics of plague there. Some of the formed natural foci of 2.MED1 still show epizootic activity and retain their epidemic potential. In this work, we carried out a phylogenetic analysis of 46 Y. pestis strains of the medieval biovar isolated in the Caucasus, the Caspian Sea, and the Northern Aral Sea regions during epidemic outbreaks and epizootics from 1922-2014. The obtained phylogenetic data, together with epidemiological and epizootological data accumulated over a period of about a hundred years, indicate the presence of two waves of penetration of the 2.MED1 branch into the Caucasus. The first occurred, apparently, in the first half of the 20th century as a result of the penetration of 2.MED1 from the foci of the Northern and North-Western Caspian Sea. The second wave was caused by the spread of 2.MED1 from the Northern Aral to the foci of the North-Western, Northern and Eastern Caspian Sea regions at the beginning of the second half of the 20th century, followed by introduction into the Pre-Caucasus and Transcaucasia. The rapid spread of 2.MED1 could be associated with the transfer of the pathogen by land and sea transport in the process of economic activity of the population.

Five Draft Genome Sequences of Historical Yersinia pestis Strains of Phylogroups 2.MED4 and 2.MED1 of the Medieval Biovar.

We announce the genome sequences of five historical highly virulent Yersinia pestis strains of the phylogroups 2.MED4 and 2.MED1 of the medieval biovar. They were the etiological agents of plague outbreaks with high mortality rates in the Northern Caspian Sea region at the end of the 19th century and beginning of the 20th.

Evolution and circulation of Yersinia pestis in the Northern Caspian and Northern Aral Sea regions in the 20th-21st centuries.

According to the whole genome SNP analysis of 38 Yersinia pestis strains isolated in the foci of the Northern Caspian and Northern Aral Sea regions in the 20th-early 21st centuries, between 1912 and 2015, the spatial and temporal structure of the 2.MED population of a medieval biovar in this region was determined. A phylogenetic branch 2.MED4 was identified which preceded the 2.MED1 branch that diverged later. 2.MED1 strains became the etiological agent of high-mortality plague outbreaks that occurred in the Northern Caspian region at the beginning of the 20th century. Later in the 20th century, the 2.MED1 branch became widespread in the Caspian Sea region, Caucasus, and vast areas of Central Asia. Based on the data of phylogenetic analysis, as well as epidemiological and epizootiological data, we reconstructed the paths of spread of the 2.MED1 branch in the Northern Caspian Sea region and in the Northern subzone of the Central Asian deserts. It is shown, that the reason for the activation of plague foci in the Northern Caspian region in the second half of the 20th century after a long inter-epizootic period caused by cyclical climate warming was the return of 2.MED1 from the foci of the Northern Aral Sea region. This led to the formation of stable plague foci in the Northern Caspian Sea region and Pre-Caucasus, which manifested epizootic activity in the second half of the 20th and early 21st centuries.

Bombali Virus in Mops condylurus Bats, Guinea.

In 2018, a previously unknown Ebola virus, Bombali virus, was discovered in Sierra Leone. We describe detection of Bombali virus in Guinea. We found viral RNA in internal organs of 3 Angolan free-tailed bats (Mops condylurus) trapped in the city of N'Zerekore and in a nearby village.

Phylogeny and Classification of Yersinia pestis Through the Lens of Strains From the Plague Foci of Commonwealth of Independent States.

The established phylogeny of the etiological agent of plague, Yersinia pestis, is not perfect, as it does not take into account the strains from numerous natural foci of Commonwealth of Independent States (CIS). We have carried out PCR and SNP typing of 359 strains and whole genome sequencing of 51 strains from these plague foci and determined the phylogenetic diversity of the strains circulating here. They belong to 0.ANT3, 0.ANT5, 2.ANT3, 4.ANT branches of antique biovar, 2.MED0, 2.MED1 branches of medieval biovar and to 0.PE2, 0.PE4a. 0.PE4h, 0.PE4t branches. Based on the studies of 178 strains from 23 plague foci of CIS countries, it was determined that the population structure of 2.MED strains is subdivided into Caucasian-Caspian and Central Asian-Chinese branches. In Central-Caucasian high-mountain plague foci in the Russian Federation (RF) the most deeply diverged branch of medieval biovar, 2.MED0, has been found. With the data obtained, the current population structure of Y. pestis species has been refined. New subspecies classification is developed, comprising seven subspecies: pestis, caucasica (0.PE2), angolica (0.PE3), central asiatica (0.PE4), tibetica (0.PE7), ulegeica (0.PE5), and qinghaica (0.PE10).

Yersinia pestis strains of ancient phylogenetic branch 0.ANT are widely spread in the high-mountain plague foci of Kyrgyzstan.

Fifty six Yersinia pestis strains, isolated over the period of more than 50 years in three high-mountain foci of Kyrgyzstan (Tien Shan, Alai, and Talas), have been characterized by means of PCR and single nucleotide polymorphism (SNP) typing methods. Seven of these strains were also characterized by means of whole genome sequencing and genome-wide SNP phylogenetic analysis. It was found that forty two strains belong to 0.ANT2, 0.ANT3 and 0.ANT5 phylogenetic branches. From these, strains of 0.ANT2 and 0.ANT3 branches were earlier detected in China only, whereas 0.ANT5 phylogenetic branch was identified for Y. pestis phylogeny for the first time. According to the results of genome-wide SNP analysis, 0.ANT5 strains are ones of the most closely related to Y. pestis strain responsible for the Justinianic Plague. We have also found out that four of the studied strains belong to the phylogenetic branch 2.MED1, and ten strains from Talas high-mountain focus belong to the phylogenetic branch 0.PE4 (sub-branch 0.PE4t). Established diversity of Y. pestis strains and extensive dissemination of the strains pertaining to the 0.ANT branch confirm the antiquity of the mentioned above plague foci and suggest that strains of the 0.ANT branch, which serve as precursors for all highly virulent Y. pestis strains, had their origin in the Tien Shan mountains.

Whole-Genome Sequencing of Vibrio cholerae O1 El Tor Strains Isolated in Ukraine (2011) and Russia (2014).

Here, we present the draft whole-genome sequence of Vibrio cholerae O1 El Tor strains 76 and M3265/80, isolated in Mariupol, Ukraine, and Moscow, Russia. The presence of various mutations detected in virulence-associated mobile elements indicates high genetic similarity of the strains reported here with new highly virulent variants of the cholera agent V. cholerae.

Draft Whole-Genome Sequence of a New Variant of Vibrio cholerae O1 El Tor Strain Isolated from a Cholera Patient in Russia.

Draft whole-genome sequencing of the Vibrio cholerae О1 El Tor clinical strain L3226, isolated in Moscow in 2010, was carried out. Various mutations in the virulence-associated mobile elements were determined in its genome that differentiated this strain from the reference V. cholerae О1 El Tor strain N16961.

Comparative analysis of biofilm formation by main and nonmain subspecies Yersinia pestis strains.

The biofilm-forming phenotype of 14 isolates from four 'nonmain' subspecies of Yersinia pestis was compared with eight isolates from the more commonly studied 'main' or epidemic subspecies of Y. pestis in this study. The four nonmain subspecies are more geographically limited, and are associated with certain mammalian hosts and regions of the Caucasus and Central Asia, whereas the main subspecies spread worldwide during the historic plague pandemics. With the main subspecies pestis, pigmentation on Congo red medium (CR(+)) correlated with biofilm formation on both abiotic and biotic surfaces. Main subspecies pestis strains that do not produce pigmentation on Congo red medium (CR(-)) have a deletion that includes the hmsF and hmsS genes known to be required for biofilm formation. CR(-) strains of the nonmain subspecies, altaica and ulegeica, differed however from pestis and, while defective for biofilms on the two surfaces, both had intact hmsF and hmsS genes. The presence of rcsA was also investigated and results showed that it occurred with a 30-bp insertion in all forms of the subspecies. These findings suggest that biofilms are regulated differently in altaica and ulegeica than they are in pestis and also indicate that the rcsA pseudogene arose early in Y. pestis evolution, increasing the ability of the strain to form biofilm and thereby increasing its effective transmission.

Molecular-genetic peculiarities of classical biotype Vibrio cholerae, the etiological agent of the last outbreak Asiatic cholera in Russia.

Molecular-genetic properties of classical biotype Vibrio cholerae strains that caused the Asiatic cholera outbreak in 1942 in Russia have been investigated for the first time. Being characterized by high-level production of cholera toxin and toxin-coregulated adhesion pili both of which are the major virulence factors, all the strains studied, in contrast to the typical cholera pathogens, were autographic requiring purine and/or amino acids added to the minimal medium for their growth. Moreover, these strains containing the structural gene hapA, as shown by the polymerase chain reaction, produced no soluble hemagglutinin/protease, which enables the vibrios to get disseminated in the environment. The peculiarities of the natural V. cholerae strains elucidated in the work are likely to be responsible for the unusual infectious and epidemic processes observed during that cholera outbreak.

Evaluation of the protective efficacy of Vibrio cholerae ghost (VCG) candidate vaccines in rabbits.

An effective Vibrio cholerae vaccine is needed to reduce the morbidity and mortality caused by this pathogen. Despite the availability of current oral vaccines with measurable efficacy, there is need for more effective vaccines with broad-spectrum efficacy in target populations. Recent studies have shown that bacterial ghosts, produced by the expression of cloned lysis gene E, possess adjuvant properties and are immunogenic. In this study, ghosts were prepared from V. cholerae O1 or O139 and evaluated as vaccines in the reversible intestinal tie adult rabbit diarrhea (RITARD) model. Rabbits were orally immunized with different doses of V. cholerae ghost (VCG) formulations. The vaccine formulations elicited high levels of serum vibriocidal titers against indicator strains. The magnitude of the response was measured as the geometric mean titer (GMT) increase for all rabbits in relation to prevaccination titers. The induction of cross protection was evidenced by the ability of serum from VCG-immunized rabbits to mediate complement-dependent killing of both the homologous and the heterologous strains. Immunized rabbits were protected against intraduodenal challenge 30 days after primary immunization. Protective immunity against challenge appeared to be dose dependent and was associated with marked inhibition of colonization. These results indicate that VCGs represent a novel approach to cholera vaccine development and constitute an effective vaccine delivery vehicle.