[Vibrio cholerae serogroups O1 and O139: susceptibility to antibiotics during 7th cholera pandemic].

The review presents data on circulation of antibiotic resistant and susceptible strains of Vibrio cholerae serogroups O1 and O139 isolated from cholera patients and healthy persons as well as from the environment, in Asia, Africa, Australia, and Europe (including New Independent States) during 7th cholera pandemic.

[Cholera caused by Vibrio cholerae O1 ctxAB- tcpA+].

Results of analysis of cholera outbreak during which V. cholerae O1 biovar El-Tor ctxAB- tcpA+ was isolated from 2 patients and 30 carriers are presented. Epidemic was caused by contamination of water source and water route of transmission. Strains identical to ones detected in humans were isolated from water of surface well in zone of water intake. Genome and VNTR-analysis of ctxAB- tcpA+ vibrios that caused outbreak in Rostov region in 2005 showed that they differed from ctxAB- tcpA- and ctxAB- tcpA+ vibrios isolated previously during and beyond of outbreaks from patients, carriers and environment and formed separate group with certain genotype. These results confirms conclusions of epidemiological analysis about imported cause of recent outbreak.

[Comparative characteristics of the preparations of hemolysin of ctx+ and ctx- Vibrio cholerae eltor and Vibrio cholerae O139 strains].

Hemolysin of ctx+ Vibrio cholerae strains was obtained and studied. Ctx+ Vibrio cholerae O1 and O139 strains produced the hemolysin during cultivation in triptone medium without FeCl3. Mol.wt. and the spectrum of lytic activities of hemolysins of ctx+ Vibrio cholerae did not differ from hemolysins of ctx- strains.

[Testing the biological activity of Vibrio cholerae on cell subcultures].

Testing the supernatants of ctx(+) strains of V. cholerae eltor and V. cholerae O139 on cell subcultures confirmed the possibility of the synthesis of hemolysin by V. cholerae under the condition of growing them in tripton medium lacking FeCl3. At the same time ctx(+) strains of V. cholerae of both serogroups retained, simultaneously with hemolysin production, their capacity for the synthesis of cholera toxin.

[Cholera at the beginning of the XXI century. Prognosis].

The worldwide epidemiological situation in cholera El Tor at the beginning of this century is presented; among its characteristic features are continued extensive epidemics and outbreaks in African and Asian countries with cases of import of this infection to other continents. Outbreaks caused by a new variant of the infective agent of cholera, Vibrio cholerae O139, are still registered at limited territories in the countries of South-East Asia. In some CIS countries (Azerbaijan, Kazakhstan and Russia) unstable situation in cholera is still preserved due to cases of infection import mainly from Asian countries, as well as to the isolation of epidemically insignificant haemolysin-positive and haemolysin-negative V. cholerae O1 and O139, containing no ctx and tcpA genes, from surface water reservoirs and other environmental objects. In Russia prognosis for cholera is still unfavorable.

[Hemolytic activity of Vibrio cholerae eltor and V. cholerae O139 toxigenic and nontoxigenic strains]. / Gemoliticheskaia aktivnost' toksikogennykh i netoksikogennykh shtammov Vibrio cholerae eltor i V.cholerae O139 serogruppy.

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.

[Role of iron ions in the production of hemolysin by toxigenic and nontoxigenic Vibrio cholerae of different serogroups]. / Rol' ionov zheleza v produktsii gemolizina toksigennymi i netoksigennymi kholernymi vibrionami razlichnykh serogrupp.

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.

[Characterization of Vibrio cholerae eltor in the city of Kazan in 2001]. / Kharakteristika kholernykh vibrionov él'tor, vydelennykh v g. Kazan' v 2001 g.

Information on V. cholerae eltor isolated in the focus of cholera in Kazan in 2001 at different periods of the outbreak is presented. The identity of strains isolated from patients, vibriocarriers and environmental objects, including their antibioticograms (sensitivity to cyprofloxacin and resistance to trimethoprim--sulfamethoxazole, streptomycin, furazolidone and nalidixic acid, which may be regarded as markers), is shown. Variable tandem repetitions in the DNA of 30 isolates strains of different origin have been determined. The results of this determination make it possible to classify all these strains as one genotype, which confirms the suggestion on the circulation of one subclone of the infective agent of cholera in the focus. As revealed in this investigation, the isolated strains are labile with respect to diagnostic phage eltor, while ctx+ strains are resistant to phage eltor ctx+.

[Hemolytic activity and toxigenicity of Vibrio cholerae of different serogroups]. / Gemoliticheskaia aktivnost' i toksigennost' Vibrio cholerae razlichnykh serogrupp.

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.

[The evaluation of the virulent properties of Vibrio cholerae O1 by using in-vitro methods]. / Otsenka virulentnykh svoistv Vibrio cholerae O1 s pomoshch'iu metodov in vitro.

The virulent properties of V. cholerae O1 (more than 1000 strains) were studied. For this purpose the following methods were used: the determination of hemolytic activity, the express method based on the determination of the speed of mannite oxidation, complex analysis and polymerase chain reaction (PCR). The comparative analysis of the results of the in vitro determination of virulence revealed that the most frequently occurring strains among the strains isolated from humans were vct+ strains (80.5%), hemolysis-negative strains (83.9%) which were virulent (faintly virulent) as determined by complex analysis (38.2%), cholerogenic as determined by the express method (60.2%). Among the strains isolated from the environment were vct- strains (87.4%), hemolysis-negative strains (63.2%) which were virulent as determined by complex (13.1%), as well as by the express method (74.3%). The data of the determination of the vct gene did not correlate with the results obtained by complex analysis. The use of complex analysis was expedient only in the detection of strains sensitive to eltor phage in the dilution routine test of V. eltor strains. The methods for the determination of virulence, available for practical laboratories, were Grieg's method for the determination of hemolytic activity and express method. PCR proved to reliable in vitro method for the determination of the vct gene.

[The characteristics of the current stage in the development of the 7th cholera pandemic]. / Kharakteristika sovremennogo étapa v razvitii 7 pandemii kholery.

The state and tendencies in the development of the epidemiological situation in cholera in the world (1961-1996) are evaluated. As revealed in this investigation, at the modern stage the development of the 7th pandemic characterized by the formation of stable and temporary endemic foci in a number of countries of Asia, Africa, Central and South America and by the import of cholera from these foci to different countries of the world, including the CIS countries and Russia. The "trigger mechanism" of epidemic manifestations in Russia is discussed, in particular the epidemic of 1994 in Dagestan used as an example. Prognostication is made on the basis of the analysis of the epidemiological situation.

[The characteristics of Vibrio cholerae isolated in Dagestan in 1994]. / Nekotorye osobennosti Vibrio cholerae, vydelennykh v Dagestane v 1994 g.

A high degree of resistance to cholera diagnostic phages and carriership of prophages characteristic of V. cholerae eltor strains vct+ were shown to be the specific features V. cholerae isolated in Daghestan during the period of June-October 1994. Among the strains under study, isolated respectively in 12 and 18 out of 19 regions of Daghestan, a high proportion was found to have resistance to tetracycline (65%) and chloramphenicol (28.6%). Moreover, some strains were found to be resistant to furagin and erythromycin. Out of 242 strains resistant to antibacterial preparations, 163 strains were found to have multiple resistance. Gentamicin, cipropfloxacin and doxicycline were shown to have high in vitro activity with respect to the strains under study.

[The virulence of Vibrio cholerae isolated under different epidemiological situations]. / O virulentnosti Vibrio cholerae, vydelennykh v razlichnykh épidemiologicheskikh situatsiiakh.

The virulence of V. cholerae isolated on the territory of Russia and other CIS countries from environmental objects and from humans in different epidemic situations during the period of 1987-1991 was studied. The analysis of the data obtained in this study revealed that intensive epidemic complications were linked with the realization of the pathogenic properties of strains, characterized by the presence of the ctx gene and the absence of hemolytic activity. As a rule, in single cases or in isolated group cases of cholera V. cholerae hemolysin-negative strains without the cholera toxin gene were isolated.

[Cholera in Ukraine and Moldova during the 7th pandemic]. / Kholera na Ukraine i v Moldove v period sed'moi pandemii.

The epidemic manifestations of cholera in the Ukraine and Moldova in 1970-1991 are analyzed. In the Ukraine the peak of cholera morbidity in 1970 was caused by infection brought to the ports of Odessa and Kerch with its subsequent spread to other territories. This infection was characterized by outbreaks transmitted through water, mainly sea water, with the isolation of Vibrio eltor toxigenic virulent strains and outbreaks of vibrio carriership of alimentary (dairy) origin with the isolation of avirulent strains. In Moldova local outbreaks of water origin were registered in 1970-1972. In both territories prolonged (up to 16 years and even longer) circulation of cholera vibrios, mainly nontoxigenic and avirulent, were registered. The retrospective epidemiological analysis and the epidemiological situation in some regions of the Ukraine in 1991 completely confirmed the prognostic importance of the division of territories into regions according to the type of epidemiological manifestations and the necessity of differentiating the measures to be taken in the system of epidemiological surveillance.

The seventh pandemic of cholera in the USSR, 1961-89.

Over the period 1961-89 a total of 1,713,057 cases of cholera were reported to WHO from 117 countries in all continents. The course of the epidemic fell into three periods: in period I (1961 to 1969), 24 countries (predominantly in Asia) reported about 419,968 cholera cases; in period II (1970 to 1977), 73 countries from Asia, Africa, Europe, and the Americas reported 706,261 cases; and in period III (1978 to 1989), 83 countries reported 586,828 cases. The global epidemic was at its most severe in 1967-74. Subsequently morbidity declined and up to 1989 had remained high and stable, with 44,000-52,000 cases per annum. In the USSR 10,723 cholera cases and carriers were reported between 1965 and 1989 from 11 republics (but not Latvia, Lithuania, Estonia, or Armenia). In 1965 and 1970-74 large-scale outbreaks of imported cholera were characteristic of the epidemic in the USSR. Thereafter morbidity declined, and sporadic cases were reported along with environmental, predominantly nontoxigenic strains of cholera vibrio. Most of the outbreaks in the 1970s were waterborne, and virulent strains containing the vct-gene were isolated from samples of water. Large-scale outbreaks continued that were associated with seafood and dairy produce that were contaminated with cholera vibrio. Clinical cases of cholera as well as a considerable number of carriers of avirulent nontoxigenic strains were reported. The epidemiological situation in the USSR is unstable, with cases of cholera and virulent strains from surface water being reported every year.(ABSTRACT TRUNCATED AT 250 WORDS)