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D Postic

Publications and source records attributed to D Postic.

62 records · Page 4Linked to original sources
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Antigenic variation of Borrelia turicatae Vsp surface lipoproteins occurs in vitro and generates novel serotypes.

As a means of avoiding the host immune response, the tick-borne relapsing fever spirochete Borrelia turicatae undergoes antigenic variation in its abundant surface lipoproteins. In this study, B. turicatae strain Oz1, serotype B, was subcultured in vitro and cloned by limited dilutions after 50 passages. Four different serotypes (serotypes A, B, E, and F) differing by their expressed Vsp lipoproteins were isolated. Using pulsed-field gel electrophoresis, we showed that the variability in surface-exposed proteins is correlated with rearrangement between different linear plasmids, defining serotype-specific plasmid profiles. Moreover, we determined the nucleotide sequence of genes encoding the VspE and VspF lipoproteins, corresponding to the two novel serotypes E and F, respectively. Our results showed that antigenic variation in B. turicatae occurs spontaneously in vitro, in the absence of immune selection.

Antigenic Variation↗
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[Borrelia species new to Russia--possible causative agents of ixodid tick-borne borreliosis].

18 Borrelia isolates, obtained in 1996-1997 from adult Ixodes ricinus collected from plants in the environs of Stavropol', were identified with the use of the polymerase chain reaction and the analysis of the polymorphism of the length of restriction fragments. Among them, in addition to B. garinii and B. afzelii, widely spread in Eurasia, 2 recently described species, B. valaisiana and B. lusitaniae, were found in Russia for the first time. Their possible spread and their importance in infectious pathology are described.

Animals↗
PubMedDate not supplied

[The first isolation of Borrelia burgdorferi sensu stricto in Russia].

18 Borrelia isolates obtained from adult ticks of the Ixodes ricinus species, collected from different plants in April 2000 in the Khostinsk region of the Krasnodar Territory in the vicinity of the health resort of Matsesta not far from Sochi, were identified by means of PCR and the analysis of polymorphism of the restriction fragments of ribosomal rrf-rrl spacer amplicon. Among them, in addition to Borrelia species, found in Russia earlier (B. garinii, B. afzelii, B. valaisiana and B. lusitaniae), the classical causative agent of Lyme borreliosis (B. burgdorferi sensu stricto) was detected for the first time. The isolated strain (lr-4721) is now kept in the collection of the Borreliosis Center of the Ministry of Health of Russia (the Laboratory of Infections Vectors at the Gamaleya Research Institute of Epidemiology and Microbiology). The probable role of this infective agent in infectious pathology in Russia is discussed.

Animals↗
PubMedDate not supplied

[The isolation of Borrelia from the tick Ixodes trianguliceps (Ixodidae) and the possible significance of this species in the epizootiology of ixodid tick-borne borrelioses].

Ixodes trianguliceps is a common tick species of the Eurasian forest zone. These ticks live probably in natural foci of ixodid tick-borne borrelioses (ITBB) from Western Europe to Transbaikalia, but their role in circulation of corresponding pathogens remains unclear. This study was performed in a natural ITBB focus located in the Perm region of Russia (near the Urals), where Borrelia garinii and B. afzelii circulate and I. persulcatus serves as their main vector. In July-August of 1994, 296 small mammals (mostly Clethrionomys glareolus) were tested for tick infestation. From these mammals, 49 I. trianguliceps and 252 I. persulcatus ticks were collected (16.3 and 83.7%, respectively). I. trianguliceps ticks were found on 33 rodents of three species: Cl. glareolus, Cl. rutilus, and Microtus oeconomus. The abundance of I. trianguliceps (on average, less than 0.2 ticks per animal) was approximately five times lower than that of I. persulcatus. I. trianguliceps larvae, nymphs, and adults (22, 15, and 5 specimens, respectively) were analyzed for Borrelia infection by plating their internal organs on the BSK-2 medium. Spirochete isolates were obtained from four nymphs. Three infected nymphs were collected from different Cl. glareolus specimens, and one was found on Cl. rutilus. According to the results of RFLP analysis, all four isolates were classified as B. garinii. This experiment is the first successful attempt to isolate one of ITBB pathogens from I. trianguliceps ticks. These ticks do not attack people, and their role in ITBB foci should be analyzed only in terms of epizootiology. The results of previous zoological-parasitological and bacteriological studies performed in the Ural region suggest that I. trianguliceps and I. persulcatus populations are maintained there by the same species of small rodents and insectivores, which mostly belong to the genera. Clethrionomys and Sorex. Many of them were identified as the reservoir hosts of Borrelia. These data, in complex with the fact of B. garinii isolation from I. trianguliceps, suggest that I. trianguliceps ticks are involved in the maintenance of Borrelia circulation in natural ITBB foci. Taking into account the low abundance of these ticks in the Ural forests, they should be regarded as an important but not principal component of the epizootic process. It is suggested that such a conclusion about the significance of I. trianguliceps ticks also pertains to ITBB foci of other regions.

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PubMedDate not supplied

[Spontaneous mixed infection in rodents with Borrelia and Leptospira].

This study was performed in a natural ITBB focus located in Perm' region of Russia. In 1993-1995, 73 root voles (Microtus oeconomus), collected in the forests, were examined by means of inoculation of internal organs on BSK-II medium. Borrelia were found in 13 animals (17.8%). According to the results in RLFP analysis 11 isolates were classified as B. garinii, 1 as B. afzelii and 1 as mixture of B. garinii and B. afzelii. In one case Leptospira, which was identified by PFGE analysis as grippotyphosa serovar, was found simultaneously with B. garinii in the BSK-II culture from urinary bladder. Our data testify to the fact of existence of mixed foci of leptospirosis and borreliosis. Moreover, one animal may serve as a reservoir host simultaneously of two different spirochetal agents.

Animals↗
PubMedDate not supplied

[The reservoir hosts and vectors of Borrelia--the causative organisms of ixodid tick-borne borrelioses in Russia].

327 Borrelia isolates from ixodid ticks of 3 species from 12 major administrative territories of Russia (from Leningrad Province in the west to Sakhalin Province in the east), as well as from forest myomorph rodents of 6 species and from skin biopsies of borreliosis patents, were identified by the PRC and RFLP methods. B. afzelii, B. garinii and B. garinii NT29 were shown to be widespread in Russia. No other Borrelia genospecies were found. The main vectors of B. afzelii and B. garinii were ixodid ticks Ixodes persulcatus and I.ricinus and their main reservoir hosts were forest myomorph rodents. In natural foci Borrelia mixed infection was observed among reservoir hosts and vectors. This determines the possibility and considerable probability of human infection caused by several Borrelia genospecies simultaneously.

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