Experimental study of the pulmonary form of plague, tularemia and pseudotuberculosis]

There was revealed a regular reduction of plague, tularemia and pseudotuberculosis bacteria count in the lungs of guinea pigs the first 12 hours after aerosol infection. Generalization of the infectious process and associated septicemia occurred in pulmonary plague and pulmonary tularemia on the 1st-2nd day, and in pulmonary pseudotuberculosis - on the 4th-5th day. Limits of accumulation of the causative agents in the organs and the blood at various stages of the infectious process were established.     

Immunogenicity of B-antigen in experimental plague and pseudotuberculosis

The results of the evaluation of the immunogenic properties of B-antigen, earlier identified in the culture fluid of Yersinia pseudotuberculosis submerged culture, with respect to experimental plague and pseudotuberculosis are presented. B-antigen has been shown to produce protective effect in guinea pigs and, probably, hamadryas baboons, but not in white mice infected with the causative agent of plague. Immunizaton with B-antigen protects guinea pigs from primary pneumonic plague caused by both capsule-forming and noncapsular Y. pestis virulent strains. Passive immunization with antibodies to B-antigen induces limitedly pronounced protective effect in guinea pigs and is not effective for white mice with respect to experimental plague. No active or passive protection of white mice or guinea pigs, infected with Y. pseudotuberculosis cultures, has been achieved by the injection of B-antigen or antibodies to it.     

Role of antibodies in protection from pseudotuberculous infection and intoxication]

Lethal doses of virulent pseudotuberculosis bacilli and antipseudotuberculosis sera of different specificity were injected to albino mice simultaneously. A high neutralizing activity of antibodies against pseudotuberculosis intoxication was demonstrated. The type-specific antibodies proved to protect the mice from the toxins of the homologous types of the microbe only. Group antibodies of plaque antiserum and serum procured from the pseudoteburculosis convalescent produced a cross antitoxic action. The antiinfectious effect from the antibody administration was weak. Apparently in pseudotuberculosis the antibodies were the principal factor of the toxin neutralization and were of auxiliary significance in the protection from the developing infection. Neutralization of pseudotuberculosis toxins with plague antiserum served as an additional confirmation of cross immunity between plague and pseudotuberculosis.     

Yersinia--flea interactions and the evolution of the arthropod-borne transmission route of plague

Yersinia pestis, the causative agent of plague, is unique among the enteric group of Gram-negative bacteria in relying on a blood-feeding insect for transmission. The Yersinia-flea interactions that enable plague transmission cycles have had profound historical consequences as manifested by human plague pandemics. The arthropod-borne transmission route was a radical ecologic change from the food-borne and water-borne transmission route of Yersinia pseudotuberculosis, from which Y. pestis diverged only within the last 20000 years. Thus, the interactions of Y. pestis with its flea vector that lead to colonization and successful transmission are the result of a recent evolutionary adaptation that required relatively few genetic changes. These changes from the Y. pseudotuberculosis progenitor included loss of insecticidal activity, increased resistance to antibacterial factors in the flea midgut, and extending Yersinia biofilm-forming ability to the flea host environment.     

Host Aspect of Territorial Expansion of the Plague Microbe Yersinia pestis from the Populations of the Tarbagan Marmot (Marmota sibirica)

Biology Bulletin - Based on ecological studies, the concept of synchronous polytopic speciation of the plague microbe Yersinia pestis from the psychrophilic saprobiontic pseudotuberculosis microbe,...     

环介导等温扩增技术检测鼠疫耶尔森菌的敏感性和特异性研究

为观察环介导等温扩增(loop-mediated isothermal amplification,LAMP)技术能否适用于我国不同疫源地鼠疫耶尔森菌所有基因组型的检测,本研究建立了一种基于3a靶序列设计特异性引物快速检测鼠疫耶尔森菌的LAMP方法.选择分离自我国11个鼠疫自然疫源地的65株野生代表性鼠疫耶尔森菌株,同...     

The yersiniae--a model genus to study the rapid evolution of bacterial pathogens

Yersinia pestis, the causative agent of plague, seems to have evolved from a gastrointestinal pathogen, Yersinia pseudotuberculosis, in just 1,500-20,000 years--an 'eye blink' in evolutionary time. The third pathogenic Yersinia, Yersinia enterocolitica, also causes gastroenteritis but is distantly related to Y. pestis and Y. pseudotuberculosis. Why do the two closely related species cause remarkably different diseases, whereas the distantly related enteropathogens cause similar symptoms? The recent availability of whole-genome sequences and information on the biology of the pathogenic yersiniae have shed light on this paradox, and revealed ways in which new, highly virulent pathogens can evolve.     

Characterization of the O-antigen gene clusters of Yersinia pseudotuberculosis and the cryptic O-antigen gene cluster of Yersinia pestis shows that the plague bacillus is most closely related to and has evolved from Y. pseudotuberculosis serotype O:1b

One of the most virulent and feared bacterial pathogens is Yersinia pestis, the aetiologic agent of bubonic plague. Characterization of the O-antigen gene clusters of 21 serotypes of Yersinia pseudotuberculosis and the cryptic O-antigen gene cluster of Y. pestis showed that the plague bacillus is most closely related to and has evolved from Y. pseudotuberculosis serotype O:1b. The nucleotide sequences of both gene clusters (about 20.5 kb each) were determined and compared to identify the differences that caused the silencing of the Y. pestis gene cluster. At the nucleotide sequence level, the loci were 98.9% identical and, of the 17 biosynthetic genes identified from the O:1b gene cluster, five were inactivated in the Y. pestis cluster, four by insertions or deletions of one nucleotide and one by a deletion of 62 nucleotides. Apparently, the expression of the O-antigen is not beneficial for the virulence or to the lifestyle of Y. pestis and, therefore, as one step in the evolution of Y. pestis, the O-antigen gene cluster was inactivated.     

The lytic activity of Yersinia pestis phage P 3d serovar

The lytic activity of plague phage II, serovar 3, with respect to 1,800 bacterial strains has been studied: 760 Yersinia pestis strains, 262 Y. pseudotuberculosis strains, 252 Y. enterocolitica strains, 166 Escherichia coli strains, 90 Shigella strains and 270 strains of other species. The phage has been found to lyse 81.8% of Y. pestis strains, 1 Y. pseudotuberculosis strain and 1 Y. enterocolitica strain. The representatives of other 19 bacterial species have proved to be resistant to the phage. Though having a wide range of action within Y. pestis, the phage does not lyse most of the strains of the causative agent of plague, isolated in certain natural foci. This fact offers promise for using the phage for the differentiation of Y. pestis.     

DNA probe for detecting Yersinia pestis and serovariant I of Yersinia pseudotuberculosis by detecting specific DNA repeating sequences]

In order to construct a DNA probe for the plague pathogen detection, we have obtained the recombinant plasmid pRD100 carrying an EcoRI-flanked 140 bp fragment from the genetically silent region of Yersinia pestis species-specific plasmid pYP1. When used as a DNA probe for hybridization of DNA from various strains of 25 bacterial species, this DNA fragment was shown to have the complementary sequences in all investigated Yersinia pestis strains (200), including the plasmid pYP1 lacking ones, and in all the studied Yersinia pseudotuberculosis serotype I strains (80). The search for the probe target in these species has led us to conclusion that it is a specific repeated DNA sequence present in more copies in Yersinia pestis than in Yersinia pseudotuberculosis serotype I. The hybridization of these sequences with the radioactive probe and 24 hours autography makes possible the detection of 1.3 x 10(5) cells of Yersinia pestis and 3 x 10(6) cells of Yersinia pseudotuberculosis serotype I immobilized on the nitrocellulose membranes. Use of the probe for analysis of the nitrocellulose membrane fixed spleen smears from animals that died of experimental plague made possible the detection of Yersinia pestis cells within 48 h.     

The sensitivity of Yersinia to bacteriophage Mu

Various representatives of the genus Yersinia were found to differ in their sensitivity to the lytic action of bacteriophage Mu cts62, which could serve as an auxiliary test for the differentiation of Y. pestis and Y. pseudotuberculosis. Among the strains under study, the causative agents of plague (34 strains) were sensitive to phage Mu cts62, while the causative agents of enteric yersiniosis (42 strains) and pseudotuberculosis (73 strains), except 3 strains with the properties of Y. pestis, were resistant to this phage.     

Enzymatic inactivation of levomycetin and penicillin by cells of the plague and pseudotuberculosis microbes that contain R plasmid depending on cultivation conditions]

The activity of enzymes, inactivating levomycetin and penicillin in the cells of plague and pseudotuberculosis microbes bearing extrachromosomal determinants resistant to a number of antibiotics was studied as dependent on some cultivation parameters: population age, aeration rate and temperature. It was shown that the highest capacity for levomycetin acetylation was characteristic of the cells in the late logarithmic and early stationary growth phages. Accumulation of levomycetin O-acetothers in the incubation medium markedly increased, when the cells were grown under the conditions of intensive aeration. An increase in the cultivation temperature up to 37 degrees C was accompanied by a reliable decrease in the activity of levomycetin acetylase in the transconjugant plague and pseudotuberculosis microbes though no correlation with the resistance levels in the same strains to the above antibiotics was observed. Optimal conditions for penicillinase production were determined. The maximum levels of penicillinase were found in the cells of Y. pestis 556/106 Rn with the episotic resistance type in the early exponential developmental phase under the aeration conditions and the temperature of 28 degrees C.     

Identification of Yersinia pestis with varied plasmid composition using monoclonal and polyclonal fluorescent immunoglobulins

Abstract The efficiency of serological identification of Yersinia pestis strains which contain different plasmids was assessed with polyclonal and monoclonal immunoglobulin preparations in the direct fluorescent antibody method. Plague polyclonal luminescent immunoglobulins recognize only those Y. pestis strains which contain pPst, pFra plasmids or both. Anticapsular plague monoclonal antibodies interact only with capsule-forming plague agent strains (pFra+) grown at 37°C. With plague monoclonal lipopolysaccharide antibodies one can identify all Y. pestis strains irrespective of their plasmid content and cultivation temperature. However, these antibodies cross-react with Yersinia pseudotuberculosis bacteria in 60% of cases. The problem of laboratory diagnosis of the plague organism, whatever its plasmid profile, can be solved through the development of a test kit involving two preparations such as plague lipopolysaccharide monoclonal luminescent antibodies and pseudotuberculosisspecific luminescent adsorbed immunoglobulins.     

Serotype differences and lack of biofilm formation characterize Yersinia pseudotuberculosis infection of the Xenopsylla cheopis flea vector of Yersinia pestis

Yersinia pestis, the agent of plague, is usually transmitted by fleas. To produce a transmissible infection, Y. pestis colonizes the flea midgut and forms a biofilm in the proventricular valve, which blocks normal blood feeding. The enteropathogen Yersinia pseudotuberculosis, from which Y. pestis recently evolved, is not transmitted by fleas. However, both Y. pestis and Y. pseudotuberculosis form biofilms that adhere to the external mouthparts and block feeding of Caenorhabditis elegans nematodes, which has been proposed as a model of Y. pestis-flea interactions. We compared the ability of Y. pestis and Y. pseudotuberculosis to infect the rat flea Xenopsylla cheopis and to produce biofilms in the flea and in vitro. Five of 18 Y. pseudotuberculosis strains, encompassing seven serotypes, including all three serotype O3 strains tested, were unable to stably colonize the flea midgut. The other strains persisted in the flea midgut for 4 weeks but did not increase in numbers, and none of the 18 strains colonized the proventriculus or produced a biofilm in the flea. Y. pseudotuberculosis strains also varied greatly in their ability to produce biofilms in vitro, but there was no correlation between biofilm phenotype in vitro or on the surface of C. elegans and the ability to colonize or block fleas. Our results support a model in which a genetic change in the Y. pseudotuberculosis progenitor of Y. pestis extended its pre-existing ex vivo biofilm-forming ability to the flea gut environment, thus enabling proventricular blockage and efficient flea-borne transmission.     

Analysis of insect toxin complex gene variability of Yersinia pestis and Yersinia pseudotuberculosis strains

The nucleotide sequences of the Tc's insect toxin complex genes have been analyzed in 18 natural strains of the main and non-main subspecies of Yersinia pestis isolated in different natural foci in the Russian Federation, as well as neighboring and more remote countries, as compared to the data on Y. pestis and Y. pseudotuberculosis strains stored in the NCBI GenBank database. The nucleotide sequences of these genes in plague agent strains have been found to be highly conserved, in contrast to those of the pseudotuberculosis agent. The sequences of two genes, tcaC and tccC2, have been found to be almost identical in Y. pestis strains, whereas other three genes (tcaA, tcaB, and tccC1) contain a few mutations, which, however, are not common for all strains of the plague agent. Exceptions are only strains of the Y. pestis biovar orientalis, whose tcaB gene is in a nonfunctional state due to a nucleotide deletion. The results suggest that the formation of the species Y. pestis as an agent of a natural focal infection with a transmissive mechanism has not resulted in degradation of the Tc's complex genes. Instead, these genes are likely to have been altered as the plague agent have been adapting to the new environment.     

Ecological aspects of the origin of Yersinia pestis,causative agent of the plague: Concept of intermediate environment

Modern phylogenies of Yersinia pestis (Logh.), causative agent of the plague, constructed using molecular-genetic methods, do not receive a satisfactory functional and adaptive interpretation and are far from being ecologically valid. We have presented an ecological scenario of the origin of the causative agent of the plague through the transition of the initial pseudotuberculosis microbe Yersinia pseudotuberculosis O:1b to a free hostal ecological niche (and a new adaptive zone) under ultracontinental climatic conditions of the Late Pleistocene (Sartan time, 22000–15000 years ago) in southern Siberia and Central Asia. An intermediate environment, i.e., the “Mongolian marmot Marmota sibirica-flea Oropsylla silatiewi” parasitic system, where the process of adaptation development of the plague microbe took place, has been characterized. A scenario based on the major principles of the modern synthetic theory of evolution opens the way to an ecological-genetic synthesis of the problem of plague origin and is an appropriate model for developing a theory of molecular evolution of pathogenic (plaguelike) microorganisms.     

Loss of a biofilm-inhibiting glycosyl hydrolase during the emergence of Yersinia pestis

Yersinia pestis, the bacterial agent of plague, forms a biofilm in the foregut of its flea vector to produce a transmissible infection. The closely related Yersinia pseudotuberculosis, from which Y. pestis recently evolved, can colonize the flea midgut but does not form a biofilm in the foregut. Y. pestis biofilm in the flea and in vitro is dependent on an extracellular matrix synthesized by products of the hms genes; identical genes are present in Y. pseudotuberculosis. The Yersinia Hms proteins contain functional domains present in Escherichia coli and Staphylococcus proteins known to synthesize a poly-beta-1,6-N-acetyl-D-glucosamine biofilm matrix. In this study, we show that the extracellular matrices (ECM) of Y. pestis and staphylococcal biofilms are antigenically related, indicating a similar biochemical structure. We also characterized a glycosyl hydrolase (NghA) of Y. pseudotuberculosis that cleaved beta-linked N-acetylglucosamine residues and reduced biofilm formation by staphylococci and Y. pestis in vitro. The Y. pestis nghA ortholog is a pseudogene, and overexpression of functional nghA reduced ECM surface accumulation and inhibited the ability of Y. pestis to produce biofilm in the flea foregut. Mutational loss of this glycosidase activity in Y. pestis may have contributed to the recent evolution of flea-borne transmission.     

Biological and physico-chemical properties of Yersinia pseudotuberculosis bacterial culture having the fra-operon Yersinia pestis

The biological and physico-chemical properties of cultures of two isogenous recombinant variants of Yersinia pseudotuberculosis were studied. The cell genomes of the cultures are distinguished from one another only by the presence or by the absence of the fra-operon, which is a determined attribute of the plague microbe capsule-forming process. The expression of the attribute is amplified by rising the microbial biomass cultivation temperature and stimulates the decrease in the viability of the bacteria and adaptation potential in vitro. In the warm-blooded owner organism the microbes of the capsule-forming recombinant variant are characterized by the greater residual pathogenicity and immunogenic ability to the experimental plague of the laboratory animals as compared to the reference-variant cells. These specific features could be explained by more expressed colonizing ability of the capsule-forming microbes provided by owner cells' stability to the phagocyte process.     

Seasonal patterns of rodents, fleas and plague status in the Western Usambara Mountains, Tanzania

Field and commensal rodents were live-trapped at three villages in an active focus of plague (Yersinia pseudotuberculosis pestis) in Lushoto District, Western Usambara Mountains, Tanga Region, Tanzania, from December 1983 to November 1984. Their flea ectoparasites were collected, identified and counted. The rodent carcasses were serologically examined for specific plague antibodies and antigens, and bacteriologically examined for bipolar staining bacilli. A total of 1758 traps were set during the 12-month period and 924 animals were caught. From these, 1037 fleas were collected. Rattus rattus (L.), Praomys natalensis (Smith) and Lophuromys flavopunctatus Thomas comprised the largest proportions of the rodent population, while Dinopsyllus lypusus Jordan & Rothschild, Ctenophthalmus calceatus Waterston and Xenopsylla brasiliensis (Baker) were the dominant flea species. Rodents were most abundantly trapped during December and January. Flea indices were highest from December to May. Human plague was most active from November to March. Rodents contained plague antibodies every month except May and July, with a peak in September. Plague antigens and bipolar bacilli were detected in rodent organs during January-April. From the product of abundance and infection rate, the most prevalent rodent hosts of plague appeared to be R. rattus, Otomys angoniensis Wroughton, P. natalensis and Pelomys fallax (Peters). Continuous integrated control of rodents and fleas was recommended, reinforced by quarantine and maintenance of a surveillance service for clinical detection, diagnosis and treatment of patients in the plague endemic area.     

Principles of speciation of the plague causative agent <Emphasis Type="Italic">Versinia pestis</Emphasis>: Gradualism or saltation?

The saltation origin of the causative agent of the plague Yersinia pestis from the pseudotuberculosis microbe Y. pseudotuberculosis O:1b has been proclaimed in recent investigations on molecular genetics. The speciation process in this case is proposed to be connected with horizontal transfer of exogenous genetic structures (such as specific plasmids pFra and pPst) into the genome of the ancestral form. The alternative “Darwinian” model of the gradual origin of the plague agent is proposed based on ecological factors. The comparison of two evolutionary scenarios, saltation and gradual, is performed; the latter seems more likely.