Ways of determination of the intensity of the epidemic process in Shigella sonnei dysentery]

Proper view on the true prevalence of Sonne dysentery characterised by polymorphous clinical picture in which many cases coursed in subclinical form could be reached only by using additional active methods for detecting the infection rate of the population. For this purpose the authors applied passive hemagglutination test which permitted to reveal the response of the organism to the antigenic stimulation in the course of two months after the sustained sickness. Over 12 000 persons were examined. According to the results of passive hemagglutination test seasonal activization of the epidemic process occurred one month earlier than it was revealed by recording of the incidence of the disease. The results of the mentioned test also showed infection rate of the population with Sonne dysentery to be as a rule greater than established by the official statistics.     

Soluble surface antigens of virulent Sh. sonnei]

The authors conducted an immunochemical analysis of the surface soluble antigen preparations (SSAP) obtained by extraction with physiological saline of the virulent Sh. sonnei microbes killed with acetone. Immunochemical studies by the immunoelectrophoresis and immunodiffusion methods in agar gel, separation on sepharose 4B and in polyacrylamide gel showed the presence of 3 groups of the antigens in the SSAP composition: 1) protein antigens, determining the commonness with the Sonne microbes of the II phase and intergenera associations with typhoid and enteropathogenic E. coli; 2) specific somatic antigen of the Boiven type present in small amounts in the SSAP; 3) specific antigens differing by specificity from the Boiven antigen detected in the microbes of the I phase only and possibly playing a role in the virulent and immunogenic properties of the causative agent.     

Use of data on Shigella contamination and immunity indices for studying the activity of the epidemic process in dysentery

The comparative study of the monthly distribution of characteristics indicating the levels of contamination with Sh. sonnei and Sh. flexneri separately, as well as the seasonal dynamics of the corresponding antibodies, in the years with high and low morbidity levels has been made with the use the indirect hemagglutination test. The possibility of using these characteristics for the evaluation of the activity of the epidemic process in dysentery caused by Sh. sonnei is shown.     

Antigenic composition of different forms of Sh. sonnei]

Data are presented on the study, with the aid of immunophoresis, of the antigenic composition of the I, II phases and R-forms of Sh. sonnei. From 5 to 7 antigens differing by thermoresistance, electrophoretic and diffuse mobility were found in the composition of microbial cells of various forms Sh. sonnei. Differences between the I phase on the one hand and cells of the II phase and R-form, on the other hand, consisted both in the quantitative composition of components of their thermostable O-antigens and in the structure of specific lipopolysaccharides of the forms.     

Immunoelectrophoretic analysis of the antigenic structure of Sh. sonnei]

The authors studied the antigenic composition of 105 Sh. sonnei strains freshly isolated from patients suffering from acute dysentery and carriers. Immunophoregrams of pure S-and R-forms species were obtained. Up to 13 antigens differing by electrophoretic and diffusion mobility and immunological specificity were revealed among soluble Sh. sonnei antigens The position of common and specific antigens was determined on the immunophoregram. Along with the thermostable somatic O-antigen detected at the I phase of the S-forms, and two thermolabile O-antigen components at the II phase, and the R-forms, there was revealed a surface, relatively thermolabile, K-antigen of A-type capable of agglutinating live bacteria in the O-antiserum; position of the latter on the immunophoregram was also determined.     

Immunogenic complexes of the soluble surface antigens of Sh. sonnei]

The comparative study of the immunogenic properties of Sh. sonnei (phases I and II) soluble surface antigens obtained by the modified method of aqueous-saline extraction and Sh. sonnei (phase I) antigen obtained by Boivin's method was made with the use of the keratoconjunctival test in guinea pigs. The protective activity of a high molecular fraction obtained by the fractionation of phase I soluble surface antigens in Sepharose 4B was studied. Boivin's antigen, when used for immunization in optimum doses, was found to have pronounced protective properties, whereas phase II soluble surface antigens showed no protective activity. A high molecular fraction obtained from phase I soluble surface antigen was found to be the most immunogenic. Protective activity was largely connected with protein antigen. The question whether protein antigen was an independent protective antigen or whether it constituted a part of a complex which determined the protective activity of a high molecular fraction remained unsolved.     

Formation of the dysentery epidemic process in three small towns]

Data are presented concerning the epidemiological analysis of Sonnei dysentery outbreaks in three towns connected by common nutrition and water supply. The epidemic processes in these populated localites were strongly interrelated. Possibilities of the effect of the water factor on the extent of Sonnei dysentery incidence were studied as well. The results of studies led to the conclusion on the presence of numerous action forms of the water factor which should be taken into consideration in carrying out prophylactic and antiepidemic measures in Sonnei dysentery.     

Use of a cryoultramicrotomy method for the purpose of studying chlamydial ultrastructure]

The method of cryoultramicrotomy was adapted for the study of the ultrastructure of HeLa and McCoy cells in monolayer cultures infected with Chlamydia, obligatory intracellular procaryotic parasites, the causative agents of ornithosis (strain Loth) and paratrachoma (strain LB 1). The cryosections were obtained by the fixation of the monolayer with 2.5% glutaraldehyde, by the gradual infiltration of precipitated cells with sucrose (0.6--1.2--1.8--2.3 M) prior to freezing in liquid nitrogen, and by the treatment of sections with 1% aqueous methyl cellulose solution before drying. This method ensured good preservation of both Chlamydia, in intracytoplasmic inclusions and host cells, as well as regular reproducibility of the results. Ultrathin sections showed a considerable polymorphism in the vegetative forms of Chlamydia, which was probably due to the structure of their cell walls. Chlamydia, were found to form small vesicle-like structures in the cavities of inclusions. The cell walls and granules inside the elementary bodies of the causative agent of ornithosis were stained with the use of phosphotungstic acid--HCl, pH 0.5.     

Differential characteristics of the I and II phases and R-form of Sh. sonnei]

Characteristics of various phases of Sh. sonnei were determined on the standard strains of Sh. sonnei of phases I and II and R-form used for the industrial production of agglutinating monoreceptor sera. Bacteria of phase I displayed a distinct morphological, cultural and serological differences. For the differentiation of Sh. sonnei of the II phase and R-form, representing the greatest difficulty in this respect, it is recommended to use phages RFfm and 6-SR, and also indirect immunofluorescence method with the application of agglutinating monophasic serum against the II phase of Sh. sonnei. In addition, a study was made of over 20 various Sh. sonnei strains at different dissociative process phases. Verification data completely confirmed the specificity of phages RFfm and 6-SR for Sh. sonnei in the II phase. The efficacy of the immunofluorescence method was confirmed on 6 strains.     

Tendencies in the epidemic process of dysentery in Ryazan

In shigellosis caused by Sh. sonnei and Sh. flexneri the epidemic process was found to have considerable difference in the tendencies and pace of its development. Shigellosis which dominated in the etiological structure at the period following 1966 was dysentery caused by Sh. sonnei; it showed the tendency towards a decrease in morbidity rate. Dysentery caused by Sh. flexneri was second in respect to the frequency of its occurrence after 1966 and showed the tendency towards increase. The simultaneous circulation of Sh. sonnei and Sh. flexneri, the differences in the epidemiology of these types of shigellosis make it imperative that they be studied separately, taking into ccount their etiological selectivity to the main routes of transmitting the infection.     

An analysis of the dysentery epidemic process in Blagoveshchensk

The retrospective analysis of dysentery morbidity in Blagoveshchensk for the period of 1960-1987 was made. The regularities linking general natural and biological factors triggering the epidemic process with dysentery morbidity among the population are emphasized. The study revealed that under the conditions of Blagoveshchensk dairy products were of major epidemic importance among factors contributing to the transmission of dysentery. Such a factor as flies also had a definite influence on the epidemic process of dysentery. Another risk factor was drinking water which influenced the epidemic process both directly and indirectly through dairy products and, probably, other foodstuffs. Reliable correlation between dysentery morbidity among the population and the quality of dairy products, tap water and the number of flies was established.     

Electron microscopic study of the I, II phases and R-forms of Sh. sonnei]

Electron microscopic study of the microbial cells of the I, II phases and the R-form was carried out. Intact cells were examined by negative contrasting, and morphological differences of various bacterial phases were shown: cells of the I phase had a relatively smooth surface, bacteria of the II phase had a smooth surface, but many cell wall fragments were split from them; the surface of the R-form cells was coarse, folded, and cell wall fragments were split from the majority of bacteria. Antigenic determinants responsible for phasic specificity in bacteria of the I and II phases were located at some distance from the external membrane of the cell wall; as to the R-form cells--they were localized on the wall.     

Latex test used for diagnosis of dysentery caused by Shigella sonnei]

The aim of this study was to evaluate the usefulness of latex reagent coated with immunoglobulins specific for antigens of phase I and II of S. sonnei for detection of these antigens in primary, mixed bacterial cultures. The study was performed on 919 fecal samples from individuals with clinical symptoms of dysentery, convalescents and from contact individuals. Material used for the test was bacterial suspension collected from McConkey or SS agars and a culture from selenite F broth heated at 100C. The results of the latex test were compared with the results of isolation of S. sonnei from the same cultures. S. sonnei was isolated from feces of 140 individuals (15.2%), while the latex test was positive in 215 cases (23.4%). The highest testing effectiveness , significantly higher than when isolation of pathogen was performed, was obtained only when 18-20 hr culture on Selenite F medium was used for latex test. The correlation between efficacy of testing for S. sonnei and phosphate content of Selenite F and a mode of its preparation was found. The latex test allows to eliminate from further bacteriological studies cultures free of S. sonnei thus it gives measurable economical profits and it shortens significantly time period of bacteriological examination.     

Manifestations of the cyclic nature of the epidemic process in dysentery

Different forms of dysentery, especially those caused by Sh. sonnei and Sh. flexneri, have been found to differ considerably in their cyclic recurrence. The development cycles of the epidemic processes of dysentery have an objective character, occur in the presence of any tendencies in the morbidity rate, and depend on the natural factors. Thus, the cycles of increase and decrease in morbidity are 3, 6, 9, 12 years for dysentery caused by Sh. sonnei and 6, 7, 8 years for dysentery caused by Sh. flexneri.     

The mechanism of the development of the epidemic process in Sonne dysentery

An epidemic outbreak of Sonne dysentery has been studied. The data of epidemiological monitoring before and after the epidemic have been analyzed. The real prognostication value of controlling the biological properties of Shigella sonnei and the increase of their intrapopulation heterogeneity at the period of the activation of the epidemic process of Sonne dysentery has been established.