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1.
Relationships between Vibrio cholerae of different origin and some serogroups with green algae Scenedesmus quadricauda in mineral medium at two temperatures have been experimentally studied. Differences in the relationships of various strains with green algae under the above-mentioned experimental conditions have been established. The study has shown that a decrease in the concentration and the death of vct+ and vct- vibrios of all strains under study occur in the linear phase of the development of algae. 3 V. cholerae strains, serogroups O139 (vct+) and O50 (vct-), have been shown to be capable of survival under the conditions mix cultivation with algae for 50-100 days. The perish of green algae is supposed to increase the survival time and multiplication of V. cholerae under experimental conditions.  相似文献   

2.
Experimental data on the comparative evaluation of the hemolytic activity of ctx+ Hly- and ctx- Hly+ V. cholerae, serogroups O1 and O139, in the process of their cultivation in different nutrient media are presented. The capacity of ctx+ V. cholerae of both serogroups cultivated under the conditions of iron deficiency, for the production of hemolysin capable of lyzing sheep red blood cells was shown. Hemolysin produced by ctx- strains of V. cholerae was synthesized under any conditions. The study of hemolysin preparations obtained from ctx- and ctx+ strains of V. cholerae, serogroups O1 and O139, revealed that they were biologically and immunologically similar.  相似文献   

3.
V. cholerae strains of different origin have been studied for the presence of cholera toxin genes (vct), the proximal part of the virulence cassette including genes zot, ace and orfU, as well as neuraminidase genes (neu), in their genomes with the use of molecular DNA probes. The possibility, in principle, for some strains to lose only a part of their virulence cassette (gene vct), while retaining its proximal part has been shown. In most cases such strains are isolated from patients with diarrhea of different severity and may probably play some etiological role, provided that the expression of the genes of additional toxins of the virulence cassette occurs. The gene expressing neuraminidase which facilitates the penetration of cholera toxin into the epithelial cells of the intestine is always present in vct+ strains and may be absent in vct- strains. The absence of genetic relationship between neuraminidases in V. cholerae O139 and V. cholerae O1 and non-O1 (non-O139) has been confirmed. The problems in connection with the integration and deletion of genetic determinants of V. cholerae virulence factors are discussed.  相似文献   

4.
非01群0139型霍乱弧菌是近年引起南亚次大陆霍乱流行的新型病原体,将其与01群霍乱弧菌的毒力特性进行对比研究对于了解其特性及研制相关的菌苗具有重要意义。本文报告了4株0139型霍乱弧菌与01群霍乱弧菌菌株的对比测定结果。发现0139型霍乱弧菌与01群霍乱弧菌有所不同,呈不透明的菌落形态,光学显微镜及电子显微镜检显示有荚膜的表型,在体内具有较高的繁殖能力并产生肠毒素,体内侵袭试验结果表明所有4株0  相似文献   

5.
The Hly region from the chromosome of Vibrio cholerae El Tor strain RV79(Hly-) and the nonhemolytic classical strain 569B were cloned into plasmid vector pBR322. Escherichia coli K-12 transformants possessing these recombinant plasmids were nonhemolytic and were detected with a 32P-labeled hly-specific DNA probe. Restriction endonuclease Sau3AI digestions of the cloned hly loci of two independently obtained RV79(Hly+) convertants, when compared with the digests of cloned RV79(Hly-) loci, revealed that an apparent alteration (10 to 15 base pairs) had occurred. In contrast, an apparent 20-base-pair deletion was present in the cloned hly locus of the classical biotype V. cholerae strain 569B. Maxicell analysis and immunoprecipitation of labeled proteins of E. coli which are encoded by the cloned hly loci of RV79(Hly+) and from nuclease BAL 31-deleted plasmids, as well as immunoprecipitation of [35S]methionine-labeled V. cholerae proteins, suggest that the hemolysin is an 84,000-dalton polypeptide.  相似文献   

6.
The dynamics of the isolation of V. cholerae cultures from various water objects on the territory of Rostov-on-Don during the period of 1994-2001 was analyzed and biological properties of 14 such cultures were studied. In the absence of epidemic complications during the above-mentioned period, a growth in the amount of V. cholerae isolates, serogroups 01 and 0139, including toxigenic V. cholerae 01, was registered. The microbiological and epidemiological aspects of the monitoring of surface reservoirs and sewage were considered and the expediency of the profound and systematic study of its results for epidemiological surveillance on cholera was emphasized.  相似文献   

7.
Filtrates from strains of Escherichia coli possessing plasmid-cloned haemolysin (Hly) genes and from strains possessing 'wild' Hly plasmids were lethal for mice on intravenous inoculation; similar doses of preparations from derivatives of these strains in which the Hly genes had been rendered non-functional or which did not possess the 'wild' plasmids were not. Live cultures of both kinds of Hly+ strain usually had a lower lethal dose for mice on intraperitoneal inoculation than the corresponding Hly- forms. Mice that had been inoculated with Hly+ forms had shorter survival times and lower numbers of organisms in peritoneal washings, lungs and blood at point of death than mice that had been inoculated with the corresponding Hly- forms; this was also so for mice pre-treated with FeSO4, a procedure which rendered mice equally susceptible to the lethal effects of the Hly+ and Hly- forms of a strain. In FeSO4-treated mice the numbers of organisms in the tissues of those dying from infection with Hly+ organisms were no higher than they were at the same time after inoculation in others given the corresponding Hly- forms; before mice of the latter category died the numbers of organisms in their tissues increased greatly. The clinical and pathological signs exhibited by mice inoculated with Hly+ organisms, but not with Hly- organisms, resembled those exhibited by mice inoculated with bacteria-free haemolysin preparations. These results suggest that haemolysin played a significant role in the pathogenesis of the disease produced by the Hly+ organisms by having a direct toxic action on the host.  相似文献   

8.
Molecular ecology of toxigenic Vibrio cholerae   总被引:7,自引:0,他引:7  
Toxigenic Vibrio cholerae is the etiological agent of cholera, an acute dehydrating diarrhea that occurs in epidemic form in many developing countries. Although V. cholerae is a human pathogen, aquatic ecosystems are major habitats of Vibrio species, which includes both pathogenic and nonpathogenic strains that vary in their virulence gene content. V. cholerae belonging to the 01 and 0139 serogroups is commonly known to carry a set of virulence genes necessary for pathogenesis in humans. Recent studies have indicated that virulence genes or their homologues are also dispersed among environmental strains of V. cholerae belonging to diverse serogroups, which appear to constitute an environmental reservoir of virulence genes. Although the definitive roles of the virulence-associated factors in the environment, and the environmental selection pressures for V. cholerae-carrying virulence genes or their homologues is not clear, the potential for origination of new epidemic strains from environmental progenitors seems real. It is likely that the aquatic environment harbors different virulence-associated genes scattered among environmental vibrios, which possess a lower virulence potential than the epidemic strains. The ecosystem comprising the aquatic environment, V. cholerae, genetic elements mediating gene transfer, and the mammalian host appears to support the clustering of critical virulence genes in a proper combination leading to the origination of new V. cholerae strains with epidemic potential.  相似文献   

9.
The recombinant plasmid RP4 omega elt carrying Escherichia coli heat-labile enterotoxin elt genes with 70-80% homology with genes vct of Vibrio cholerae has been constructed. We used this plasmid to determine localization of the cholerae toxin genes vct on the map of Vibrio cholerae cholerae. Two types of the donors were revealed in matings of 10 strains of V. cholerae cholerae 569B/RP4 omega elt with the polyauxotrophic recipients RV31 and RV175: some strains had enhanced frequency of mobilization of ilv-1 and lys-6 markers, the others--of trp-1. Our data suggest that structural vct genes are located within two regions of V. cholerae cholerae 569B chromosome: trp-1 and ilv-1--lys-6.  相似文献   

10.
Abstract The extent of contamination of a freshwater lake with Vibrio cholerae 0139 Bengal and the toxigenicity of all the V. cholerae isolates recovered during the period of the study were examined during and after an explosive outbreak of 0139 cholera in Calcutta. Strains biochemically characterized as V. cholerae could be isolated throughout the period of study examined from the freshwater lake samples. Most probable number of V. cholerae belonging to the 0139 serogroup in surface waters was 3 to 4 per 100 ml during major part of the study but isolation of this serogroup from sediment and plankton samples was infrequent. Of the total of 150 strains recovered, 23 (15.3%) agglutinated with the 0139 antiserum while the remaining belonged to the non-O1 non-O139 serogroups. None of the strains agglutinated with the O1 antiserum. All the 23 strains of V. cholerae O139 produced cholera toxin while 7.9% of the 127 non-O1 non-O139 strains also produced cholera toxin. Resistance to ampilicillin, furazolidone and streptomycin was encountered among strains belonging to both V. cholerae O139 and V. cholerae non-O1 non-O139 strains, but the percentage of resistant strains in the former was much higher than in the latter. During this cholera epidemic, possibly due to the introduction of large numbers of toxigenic V. cholerae such as the O139 serogroup, there was an increase in the number of toxigenic vibrios among the innocuous aquatic residents. This presumably occured through genetic exchange and, if substantiated, could play an important role in the re-emergence of epidemics.  相似文献   

11.
Abstract Vibrio cholerae belonging to the recently described serogroup 0139, which are responsible for the current cholera epidemics in India and Bangladesh, were shown to express pilus-like structures partially cross-reacting with the toxin-coregulated pilus of V. cholerae strain (0395) belonging to the 01 serogroup and classical biotype. The 0139 pili were composed of 20 kDa subunit proteins which were antigenically related to the 20 kDa pilus protein of another diarrhoeagenic non-01 V. cholerae strain (serogroup 034) isolated earlier. The pili described in this study were found to be involved in the intestinal colonization process and, therefore, may contribute towards the virulence of the 0139 epidemic isolates.  相似文献   

12.
T lymphocytes and macrophages from Listeria-infected mice were used to evaluate the processing and presentation of live Listeria monocytogenes in vitro. Antigen presentation to T cells was quantitated by interleukin-2 production. In contrast to inert antigens such as heat-killed Listeria, live bacteria were processed and presented poorly. To evaluate the role of hemolysin (Hly), we used isogenic pairs of Hly+ and Hly- Listeria as antigens. In contrast to live Hly- bacteria, which were presented as well as heat-killed Listeria, live Hly+ bacteria were presented poorly. Hly+ bacteria also inhibited the presentation of heat-killed Listeria. This effect was apparent with as few as 10 bacteria/macrophage and was not due to loss of macrophage viability or decreased Ia expression after exposure to the live bacteria. With respect to murine listeriosis, the LD50 values for the Hly- strains were at least 1000 times higher than those for the Hly+ strains. These results suggest that the ability of Hly+ bacteria to inhibit antigen processing and presentation may be an important determining factor in Listeria infection and immunity.  相似文献   

13.
霍乱弧菌和副溶血弧菌分离株的gyrB基因系统发育分析   总被引:1,自引:0,他引:1  
依据gyrB基因部分编码序列构建系统发育树以分类和鉴别霍乱弧菌和副溶血弧菌,并探讨其种系发生关系。扩增并测序13株霍乱弧菌、8株副溶血弧菌、2株嗜水气单胞菌及1株类志贺邻单胞菌的gyrB基因(编码DNA促旋酶B亚单位)序列,并采用距离法与最大似然法构建系统发育树。两种方法所构建的树结构完全一致,霍乱弧菌、副溶血弧菌、嗜水气单胞菌及类志贺邻单胞菌各自形成一个独立的簇。其中,霍乱肠毒素基因(ctxA)阳性的霍乱弧菌(8株O139群与2株O1群ElTor型)聚类成一分枝;3株副溶血弧菌临床株(1株2002年流行株,2株2004年分离株)与1日本菌株及2001年1株自环境分离的毒力株聚类。系统发育分析靶分子gyrB基因可以良好区分上述4种常见病原菌。产毒O139群霍乱弧菌与产毒O1群ElTor型霍乱弧菌关系密切。副溶血弧菌环境毒力株与本地区临床主要流行株在系统发育关系上较为接近,可能是潜在的致病菌。  相似文献   

14.
Vibrio cholerae is a waterborne bacterium native to the aquatic environment. There are over 200 known serogroups yet only two cause cholera pandemics in humans. Direct contact of human sewage with drinking water, sea-born currents and marine transportation, represent modes of dissemination of the bacteria and thus the disease. The simultaneous cholera outbreaks that occur sometimes in distant localities within continental landmasses are puzzling. Here we present evidence that flying, non-biting midges (Diptera; Chironomidae), collected in the air, carry viable non-O1 non-O139 serogroups of V. cholerae. The association of V. cholerae with chironomid egg masses, which serve as a V. cholerae reservoir, was further confirmed. In simulated field experiments, we recorded the transfer of environmental V. cholerae by adult midges from the aquatic environment into bacteria-free water-pools. In laboratory experiments, flying adult midges that emerged from V. cholerae (O1 or O139) contaminated water transferred the green fluorescent protein (GFP)-tagged pathogenic bacteria from one laboratory flasks to another. Our findings show that aerial transfer by flying chironomids may play a role in the dissemination of V. cholerae in nature.  相似文献   

15.
The hemolytic activity of ctx- and ctx+ V. cholerae, serogroups eltor and O39, in a medium free of FeCl3 was studied. During the cultivation in this medium, the strains of both V. cholerae serogroups proved to be capable of lysing sheep red blood cells in the Graig test, irrespective of the presence of ctx genes. The cultivation of V. cholerae ctx+ strains of both serogroups under such conditions facilitated the production of hemolysin with the same spectrum of lytic activity as hemolysin produced by ctx- strains.  相似文献   

16.
Infection of V. cholerae 01 (classical and eltor biovars) cells with the temperate cholera phage 139 derived from V. cholerae serogroup 0139 followed by integration of the phage genome into the bacterial chromosome significantly increased the production of cholera toxin, the main virulence factor. The level of toxin biosynthesis in the lysogenic V. cholerae classical strain increased 3-fold and that in V. eltor thirty times in comparison with the parental strains. Increased production of cholera toxin was not associated with an increase in the number of copies of genes involved in its biosynthesis but seemed to be due to changes in toxinogenesis regulation.  相似文献   

17.
Vibrio cholerae El Tor RV79 is phenotypically nonhemolytic; however, strongly hemolytic convertants are occasionally observed on blood agar plates. We have cloned DNA sequences corresponding to the hemolysin determinant from RV79 (Hly+) in the lambda L47.1 and pBR322 vectors. A 2.3-kilobase fragment of V. cholerae DNA was found to be necessary for hemolytic activity. This cloned DNA sequence was used as a probe in Southern blot hybridization analysis of chromosomal restriction digests of a variety of El Tor and classical biotype V. cholerae strains. In all cases, DNA fragments with the same electrophoretic mobilities hybridized to the Hly probe. The results presented demonstrate that the cloned hemolysin determinant is the hly locus. By using mutator vibriophage VcA-3 insertion to promote high-frequency transfer, the hly locus was mapped between arg and ilv on the V. cholerae RV79 chromosome.  相似文献   

18.
A total of 20 ctx- and 16 ctx+ V. cholerae eltor strains, 20 ctx- and 22 ctx+ V. cholerae O139 strains were under study. Hemolytic activity was tested in modified Greig test with sheep, guinea pig and rabbit red blood cells. The comparative study of the hemolytic properties of V. cholerae O1 and O139 under different conditions of cultivation demonstrated their capacity of lysing sheep red blood cells (SRBC) irrespective of the presence of toxigenic properties. A wider spectrum of lytic activity of ctx- strains in Greig test with respect to red blood cells of different animals and the capacity of lysing SRBC, most resistant to the action of toxin, may be due to a considerably greater content of Hly+ clones in their population.  相似文献   

19.
The analysis of the data on the isolation of V. cholerae from different ecological systems indicates that V. eltor do not constantly inhibit the rivers and sea at the territory under control. Hemolytically active V. cholerae without the vct gene, found to be faintly virulent and avirulent when studied on suckling rabbits used as a model and when evaluated by the complex method, show no tendency towards epidemic spread in the presence of conditions for the realization of the transmission of vibrios by the water route.  相似文献   

20.
GA Price  RK Holmes 《PloS one》2012,7(8):e42434
The secreted colonization factor, TcpF, which is produced by Vibrio cholerae 01 and 0139, has generated interest as a potential protective antigen in the development of a subunit vaccine against cholera. This study evaluated immunogenicity/protective efficacy of a TcpF holotoxin-like chimera (TcpF-A2-CTB) following intraperitoneal immunization compared to TcpF alone, a TcpF+CTB mixture, or CTB alone. Immunization with the TcpF-A2-CTB chimera elicited significantly greater amounts of anti-TcpF IgG than immunization with the other antigens (P<0.05). Protective efficacy was measured using 6-day-old pups reared from immunized dams and orogastrically challenged with a lethal dose of El Tor V. cholerae 01 Inaba strain N16961. Protection from death, and weight loss analysis at 24 and 48 hours post-infection demonstrated that immunization with TcpF alone was poorly protective. However, immunization with TcpF+CTB was highly protective and showed a trend toward greater protection than immunization with CTB alone (82% vs 64% survival). Immunization with the TcpF-A2-CTB chimera demonstrated less protection (50% survival) than immunization with the TcpF+CTB mixture. The TcpF-A2-CTB chimera used for this study contained the heterologous classical CTB variant whereas the El Tor CTB variant (expressed by the challenge strain) was used in the other immunization groups. For all immunization groups that received CTB, quantitative ELISA data demonstrated that the amounts of serum IgG directed against the homologous immunizing CTB antigen was statistically greater than the amount to the heterologous CTB antigen (P≤0.003). This finding provides a likely explanation for the poorer protection observed following immunization with the TcpF-A2-CTB chimera and the relatively high level of protection seen after immunization with homologous CTB alone. Though immunization with TcpF alone provided no protection, the additive protective effect when TcpF was combined with CTB demonstrates its possible value as a component of a multivalent subunit vaccine against Vibrio cholerae 01 and 0139.  相似文献   

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