Reduction of the biological activity of Vibrio cholerae culture filtrates exposed to neuraminidase inhibitors]

Experiments were conducted on a model of edema of albino mouse paws; a study was made of the effect of neuraminidase inhibitors on the cholerogenic effect of a filtrate of cholera vibrio culture. It appeared that addition to the filtrate of inhibitors depressed its biological activity. Since no cholerogenic action was possessed by the purified neuraminidase preparations from the cholera vibrios it was suggested that there existed a chemical affinity between the region of cholerogen responsible for fixation on the cell membranes and the active neuraminidase centre.     

Houseflies (M. domestica L.) as transmitters of the agent of cholera

The authors present the experimental results of study of the role played by domestic flies in the spread of cholera causative agents. It was found that cholera microbes survived on the external surface of flies for 5 to 7 days, and in the insect organism--in the course of their whole life. Cholera vibrios underwent no sharp changes in the organism of flies. By means of individual infection method and keeping of flies excluding a possibility. By means of individual infection method and keeping of flies excluding a possibility of repeated autoinfection it was revealed that cholera vibrios could multiply in the organism of domestic flies. The infected insects can discharge cholera vibrios for a long time into the external environment and contaminate food.     

Electron microscopy of cholera vibrios from the intestinal contents of infected suckling rabbits]

Electron microscopic study of the cells of classic, El Tor and NAG-vibrios showed them to be no different by the structure type from the cells of ofter Gram-negative bacteria. A characteristic peculiarity of the cholera vibrios revealed after their passage through the intestine of nursling rabbits was the presence of microcapsules and protrusions of the areas of the wall membranous apparatus.     

Cholera vibrios lectins as main pathogenicity and persistence factors (biotechnological aspects of use)

Literature data and results of our studies of lectins are analyzed in the review. All the leading pathogenicity factors of cholera vibrios that possess enzymatic activity--cholera toxin, hemolysin, neuraminidase, chitinase have several lectin domains, that determine not only their pathogenetic role but also open perspectives for their use in medical practice. At the same time the variable receptor profile of cholera vibrios cells of various biovars and epidemical significance established with hemagglutination inhibition reaction by carbohydrates could be used to develop new principles of testing and typing of cholera vibrios.     

The agglutinability of cholera O-monoclonal immunoglobulins]

A set of 10 monoclonal antibodies specific for vibrio species and of 5 monoclonal antibodies specific for serovar (Ogawa) was studied. These monoclonal antibodies were directed toward V. cholerae O1 antigen in agglutination reaction and on slide plates. Monoclonal antibodies agglutinating typical strains of cholera vibrios with titration range from 1: 6000 to 1: 25,000 were selected. MA were revealed to interact with cholera vibrio strains with reduced agglutinability. The set of agglutinating O monoclonal immunoglobulins was developed for laboratory identification of cholera O1 vibrios.     

Phage typing of cholera vibrios with different sets of phages]

A comparative study was made of two sets of Mukerjee and Drozhevkina-Arutyunova's bacteriophages in typing 514 strains of the El Tor vibrios and 45 strains of clasic biotype. It was shown that the Mukerjee or Drozhevkina-Arutyunova's phages could be used for the typing of cholera vibrios. The phages of the latter set prove to detect more phage types (18 against 11); they determine both the phage type and the biotype at the same time. The typing of cholera vibrios of both biotypes is possible, and the percentage of nontyping strains left is comparatively low (5.2 against 23.5 after Mukerjee). A table of the phage correspondence was made; it permits to obtain comparable data in using any set of the typing phages.     

The use of a CHO cell culture in studying Vibrio cholerae grown under different conditions]

Studies of biological activity of cholera vibrios in cultures of chinese hamster ovary cells (CHO) have revealed their strong dependence on culture conditions. Elongation of CHO cells is caused only by choleragenic strains. Under stationary conditions of culture the vibrios were found to release haemolisin into the medium and had a cytotoxic effect. Most of cytotoxic supernatants exhibited a neuraminidase activity. Proteolytic activity was less dependent on the vibrio culture conditions. Strains with a high proteolytic activity caused rounding of the CHO cells.     

Evolution of the epidemiology of cholera

The problems of the evolution of cholera at the stages of its pandemic spread are described. A short characterization of endemic zones in the countries of Asia, Africa and Latin America, stipulating the preservation of infection and the appearance of periodic epidemics in the world, is presented. Special attention is paid to the genesis of epidemic outbreaks in endemic and introduced foci of cholera, differing in the specific features of their formation and the accumulation of the epidemic variant of the infective agent in aqueous habitat. The role of the ecosystem of surface water reservoirs in the prolonged survival of cholera vibrios is evaluated. The necessity of the detailed study of the mechanisms and forms of existence of serogroup 0139 vibrio in open water reservoirs is substantiated. In the system of epidemiological surveillance on cholera the microbiological monitoring of environmental objects assumes the leading importance.     

Systemic immunity of experimental animals immunized with cholera vaccines

The levels of antitoxic and vibriocidal antibodies in the sera of suckling rabbits after their parenteral immunization with cholera vaccine, cholera toxoid and a combination of cholera vaccine and toxoid were examined. Cholera vaccine induces intensive production of vibriocidal antibodies, and cholera toxoid, of antitoxic antibodies. The parenteral administration of the serum of rabbits immunized with cholera toxoid neutralized the action of cholera toxin in the small intestine of suckling rabbits. The complex preparation combines the properties of the corpuscular vaccine and the toxoid, inducing the production of both vibriocidal and antitoxic antibodies.     

The use of the gene hybridization method for the identification of epidemiologically dangerous strains of cholera vibrios

Using the labeled DNA fragments containing the genes for cholera toxin the strains of cholera vibrios were studied for the presence of cholera toxin genes. Vibrio cholerae strains isolated from natural water reservoirs under the favourable epidemic situation do not contain the cholera toxin genes. The DNA hybridization method was compared with other methods used in research and practical work for estimation of epidemic importance of cholera vibrios.     

Specificity of lectin receptors of cholera vibrios

Spectrum of carbohydrate specificity of lectin receptors of epidemically significant cholera vibrios (ctx(+) tcp(+) Hly(-)) as well as non epidemic hemolytic variants with or without tcp A gene (ctx(-) tcp(-) Hly(+), ctx(-) tcp(+) Hly(+)) was studied under the carbohydrates-mediated inhibition of hemagglutination between human erythrocytes of four blood groups and sheep erythrocytes. It was demonstrated that in toxigenic cultures lectin receptors specific for glucose, mannose, sacharose, lactose dominate whereas receptors specific for aminosugars are virtually absent. The latter are detected in hemolytic vibrios that can explain their ecologic flexibility.     

Epidemiological patterns of the import and spread of El Tor cholera]

The paper is a response to the paper by A. K. Akiev published in 1974 in the "Journal of Microbiology Epidemiology and Immunobiology": "Concerning the Epidemiology of El Tor cholera Abroad". The opinion of the author concerning the origin of El Tor infection in 1970, the sources of infection, and the factors of its transmission is critisized. Literature data and personal observations explaining the regularities of importation and spread of El Tor cholera as an intestinal infection are presented; these data are against the view of Akiev on El Tor cholera as a disease with a natural nidality caused by freely living vibrios.     

Determination of the degree of similarity of cholera and NAG vibrios

The numeric taxonomy taking into account 80 signs has demonstrated the similarity of NAG and cholera vibrios, the average similarity coefficient exceeding 80 %. Among NAG vibrios, 53 % of the strains have been found to deviate from the central strain of V. cholerae mainly with regard to their utilization of the sources of carbon. The use of the citrate sign for the study of the biological properties of NAG vibrios is proposed.     

Toxins of Vibrio cholerae

Surveyed in the paper are published data on properties, biological activity, genetic determinants and action mechanisms of recently known toxins produced by different strains of Vibrio cholerae irrespectively of their capacity for the synthesis of choleric toxin--the main virulence factor. Their possible importance both for the general clinical pattern of cholera provoked by cholerogenic agents and as independent virulence factors causing diarrhea without cholera is elucidated. The sets and levels of expression of additional toxins can differ for different pathogenic clones and they can correspondingly condition degrees of their epidemic and etiological safety.     

Long-term survival of E1 Tor cholera vibrios in naturally contaminated sewage]

El Tor cholera vibrios of Ogava serological type were revealed in the sewage of the locomotive shed for 15 months. In experiment with an oil catcher in naturally infected sewage El Tor vibrios survived 36 days, in storage of this sewage at the laboratory--39 days, in the artificially infected sewage of a settlement and of a milk plant--2 and 11 days, respectively, in the oil and disel fuel--14 months. Consequently, El Tor vibrio can survive in the sewage with a high oil product content for a long time.     

Morphological changes caused by the dermonecrosis factor of the causative agents of cholera and various other intestinal infections

Intra- or subepithelial focal purulent inflammation with necrosis of exudating leucocytes during 1-2 days is developed in consequence of intradermal injection of the living cholera vibrios, cultured on membrane agar, or their supernatants. Sometimes coagulative necrosis of cover epithelium arises without preliminary purulent inflammation stage from the very beginning. Intradermal injection of living cholera vibrios leads to the development of coagulative necrotic foci in derma too. The vascular genesis of alterations mentioned above is supposed.     

Comparative evaluation of the functional activity of different immunoglobulin classes in cholera]

The immunological activity of specific immunoglobulins in different forms of cholera infection was studied with the use of the indirect immunofluorescent method. The forms of cholera infection were shown to be related to the physico-chemical spectrum of antibodies: patients with the pronounced clinical symptoms of cholera produced serum IgM, including antigen -- antibody complex, more actively and in a greater amount; patients with faintly pronounced and asymptomatic infection produce highly active IgG. The competitive action of immunoglobulins of different classes in their simultaneous reaction with O antigen of Vibrio cholerae is shown. The mechanism of the competitive action of different immunoglobulin classes is supposed to play some role in the process of the sanation (with highly active IgM) or detoxication (with highly active IgG) of the organism.     

Pathogenicity of nonagglutinating vibrios]

In studying the pathogenicity of nonagglutinating vibrios it was established that the majority of the strains isolated from the patients suffering from enteritis possessed enteropathogenic properties which were revealed in the trials on nursling rabbits and on the isolated intestinal loop a of an adult rabbit. In difference to the cholera vibryos, these microorganisms produced no typical cholerogenicity syndrome expressing, however, a number of enteropathogenic properties: caused diarrhea, overfilling of the intestine with fluid, etc. Autopsy showed a typical enterocolitis picture, confirmed by histological studies. Nonagglutinating vibrio cultures isolated from the water and from healthy persons possessed no enteropathogenic properties. An isolated intestinal loop of an adult rabbit proved to be the most sensitive experimental model.     

Inhibiting effect of cholera vibrio neuraminidase in Rauscher mouse leukemia]

A study was made of the inhibitory effect of neuraminidase of cholera vibrio in mouse Rauscher leukemia. It was shown that the processing of cells of the spleen of mice suffering from leukemia with neuraminidase (in a dose of 50 units/ml and more) significantly inhibited the capacity of these cells to induce leukemia in their injection to BALB/c mice. In the mentioned concentration neuraminidase injected repeatedly parenterally produced no therapeutic effect in Rauscher leukemia.