The world-wide pandemic and drug resistance of the causative agent of Grigor'ev-Shiga dysentery

One of the factors facilitating the global pandemic of Grigor'ev-Shiga dysentery is considered in detail. All Shigella dysenteriae 1 strains, irrespective of the geographical zone of their spread, showed medicinal resistance. As pandemic developed, the spectrum of medicinal resistance constantly increased in all hyperendemic foci. The presence of pronounced relationships between the strains circulating in each of three hyperendemic foci and the strains circulating in different hyperendemic foci could be observed. The necessity of paying greater attention to this dangerous infectious disease, and especially to the problems related to the medicinal resistance of its causative agents, is emphasized.     

Some controversial questions on the epidemiology of intestinal infections. Report I. Significance of the dose and the biological properties of the causative agent in the epidemiology and the clinical picture of salmonelloses and dysentery]

On the basis of analysis of literature and personal observations and studies the authors explain a number of epidemiological and clinical peculiarities of intestinal infections with various pathogenic doses of the causative agents; under the term pathogenic dose is understood the minimal amount of microbes necessary for the onset of the disease with the natural mechanism of transmission of the infection. Regularities of the effect of the pathogenic dose of the causative agent on the epidemic process common for intestinal infections were formulated.     

Immunotropic properties of the causative agent of viral hepatitis C

In this review the immunomodulating properties of the causative agent of viral hepatitis C are characterized on the basis of experimental data, obtained by Russian and foreign researchers during recent 3-5 years. The short characterization of the causative agent is presented and a number of adaptation mechanisms making it possible for hepatitis C virus to resist the action of the immune protective system of the host are considered. The role of individual protein products of the virus in the immunopathogenesis of the disease and the mechanisms of their action on the molecular level are discussed in detail on the basis of the results of mouse and in vitro experiments.     

Dynamics of bacterial polysensitization in acute dysentery in children depending on the species of the causative agent

Studies on polysensitization, evaluated by the neutrophil damage index, have been made with the use of dysenterin and the allergens of hemolytic staphylococci, enterococci and Escherichia coli. The studies have revealed that both specific and nonspecific sensitization to hemolytic staphylococci and enterococci is higher in dysentery caused by Shigella flexneri than in dysentery caused by S. sonnei and has the tendency to increase in the course of the disease.     

Relation of the epidemiological characteristics of dysentery to the biological properties of the causative agents

The main forms of the epidemic manifestation of dysentery induced by different causative agents in 1975-1980 were revealed. During these years the cases of dysentery induced by Shigella sonnei, biovar II, were found to prevail (82.0-90.1%) both at the periods between epidemics and at the periods of the seasonal rise of morbidity. The experimental infection of white mice by intraperitoneal inoculation revealed no relationship between the seasonal rise of morbidity in dysentery and the virulence of its causative agents.     

Drug resistance of the causative agent of Grigo'rev-Shiga dysentery (Shigella dysenteriae 1)isolated in the USSR

Forty strains of S. dysenteriae 1 isolated in the USSR within 1986-1988 were tested for their resistance to 11 antibacterial drugs. It was shown that 92.5-97.5 per cent of the isolates were resistant to chloramphenicol (Cm) and tetracycline (Tc), 22.5 per cent to streptomycin (Sm), 17.5 per cent to nalidixic acid (Nal) and 10 per cent to ampicillin (Ap) and polymyxin (Pm). Resistance to Cm Tc (51.4 per cent) and Cm Tc Nal (13.5 per cent) represented the predominating phenotype. 35 per cent of the strains carried conjugative R plasmids. In the majority of the cases, the determinants of resistance to Cm and Tc were transferred, which must define the high frequency of the strains resistant to Cm and Tc. All the tested strains were sensitive to gentamicin, neomycin, rifampicin, cefamezin and ciprofloxacin. Since the strains of S. dysenteriae 1 proved to be highly sensitive to the tested drugs it appeared possible to consider them as the drugs of choice in etiotropic therapy of patients with dysentery caused by the pathogens of the Grigoryev-Shiga group.     

Seeding efficiency of the causative agent of dysentery as an index of the intensity of the epidemiologic process]

A study was made of the character and extent of interrelationship between the indices of dysentery morbidity and the indices of the seeding efficiency of dysentery bacilli persons who did not apply for medical aid. Establishment of such interrelationship permitted the authors to suggest the use of a more objective index of the seeding efficiency of dysentery bacilli, along with morbidity indices, for the assessment of the intensity of the epidemic process in this infection. On the basis of investigations carried out the authors came to the conclusion that a tendency to the increase of dysentery incidence the last few years chiefly bore a "statistical" character and was due to the improved detection of patients and carriers.     

Antigenic properties of the electrophoretic fractions of the causative agent of melioidosis

Antisera to the antigens of 5 fractions, isolated as the result of the separation of P. pseudomallei aqueous saline extract by continuous electrophoresis in the vertical block of granulated gel, have been obtained. Immunoelectrophoresis with the use of P. pseudomallei aqueous saline extract has revealed that antisera to electrophoretic fractions contain antibodies mainly to the antigens of the corresponding fractions, which shows that this technique ensures the effective separation of P. pseudomallei biopolymers by their electrophoretic motility and molecular weight. These antisera differ in their species specificity. Thus, antisera to antigens with anode motility have been found to contain antibodies mainly to P. pseudomallei antigens and antisera to electroneutral antigens or to those with cathode motility, to P. pseudomallei and P. mallei antigens.     

Adenylate cyclase of the causative agent of plague: its purification and properties

Three forms of adenylate cyclase have been detected in Y. pestis: membrane-bound, cytoplasmic and extracellular. Extracellular adenylate cyclase has been purified so as to achieve a homogeneous state, and some of its physicochemical parameters have been investigated. In the process of purification the initial preparation of this enzyme has been subjected to heating at 100 degrees C for 15 minutes, fractionation with ammonium sulfate, and gel filtration on Sephadex G-100. The homogeneity of adenylate cyclase has been confirmed by electrophoresis in 7.5% polyacrylamide gel and precipitation by the plague agglutinating serum. The enzyme has been found to have a molecular weight of 30,000 daltons and to show the optimum activity at pH 7.0-7.2 and at a temperature between 37 and 40 degrees C. Monospecific rabbit serum to the homogeneous preparation of adenylate cyclase has been obtained.     

Patterns determining the dynamics of the epidemic process in Sonne dysentery and its relation to the type of causative agent]

The results of studying the dynamics of the epidemic process of dysentery, based on the data from 3 districts of Moscow, are presented. The study revealed the periodicity of 3 years in the course of the epidemic process of dysentery, occurring against the background of a considerable predominance of Sh. sonnei, biochemical type 2. The use of the cohort method for analyzing the age structure of dysentery cases showed the possibility of using this method to find out to what extent the epidemic process repeatedly affected the same groups of population.     

Trends in the spread of Boyd 4 dysentery and the characteristics of its clinical picture and of the biology of its causative agent

The data on the proportion of S. boydii 4 in the general structure of the causative agents of dysentery, as well as in the intraspecific structure of S. boydii, in some areas of the USSR in 1977-1981 are presented. S. boydii strains 4, circulating in one of the areas where their proportion considerably increased in 1980-1981, corresponded to their taxonomic position in their biological properties, while forming a single biochemical variant according to the character of the fermentation of sorbitol, maltose and arabinose. These strains gave identical antibiotic sensitivity charts and showed pronounced multiple resistance to antibiotics, including ampicillin. The clinical features of the diseases caused by S. boydii 4 consisted in the sharply defined prodromal period and pronounced systemic toxicosis at the initial period of the disease, accompanied by the syndrome of moderate colitis localized mainly on the right side.