Bacterial Dysentery

Bacterial dysentery is an acute anthroponotic infectious disease with a fecal-oral transmission mechanism. Characterized by general intoxication and predominant damage to the mucous membrane of the distal colon, cramping abdominal pain, frequent loose stools mixed with mucus and blood, tenesmus.

Brief historical information

Clinical descriptions of the disease were first given in the writings of the Syrian physician Areteus of Cappadocia (1st century BC) under the name “bloody or strained diarrhea” and in ancient Russian manuscripts (“bloody womb”, “washed”).

In the medical literature of the 17th – 19th centuries, the tendency of the disease to spread widely in the form of epidemics and pandemics was emphasized. The properties of the main causative agents of dysentery were described at the end of the 19th century (Raevsky A.S., 1875; Chantemess D., Vidal F., 1888; Kubasov P.I., 1889; Grigoriev A.V., 1891; Shiga K., 1898), later, some other types of pathogens were discovered and described.


The causative agents are Gram-positive non-motile bacteria of the genus Shigella of the Enterobacteriaceae family. According to the modern classification, shigellas are divided into 4 groups (A, B, C, D) and, accordingly, into 4 species – S. dysenteriae, S. flexneri, S. boydii, S. sonnei. Each of the species, except Shigella Sonne, includes several serovars. Among S. dysenteriae, 12 independent serovars (1 – 12) are distinguished, including Grigoriev-Shigi (S. dysenteriae 1), Stutzer-Schmitz (S. dysenteriae 2) and Large-Sachs (S. dysenteriae 3-7). S.flexneri includes 8 serovars (1-6, X and Y), including Newcastle (S.flexneri 6). S. boydii includes 18 serovars (1 – 18). S. sonnei is not differentiated serologically. In total, there are about 50 Shigella serovars. The etiological role of different shigella is not the same. Shigella Sonne and Shigella Flexner, the causative agents of the so-called large nosological forms, are of the greatest importance in almost all countries. The etiological significance of individual shigella serovars is not the same. Among S. flexneri, subserovars 2a, lb, and serovar 6 dominate; among S. boydii, serovars 4 and 2;

The causative agents of bacillary dysentery are distinguished by enzymatic activity, pathogenicity and virulence. All shigella grow well on differential diagnostic media; temperature optimum 37 °C, Sonne bacteria can multiply at 10-15 °C.

Shigella is not very stable outside the human body. The virulence of bacteria is quite variable. The virulence of Shigella Flexner, especially Podserovar 2a, is quite high. Shigella Sonne are the least virulent. They are distinguished by high enzymatic activity, unpretentiousness to the composition of nutrient media. They multiply intensively in milk and dairy products. At the same time, the time of their preservation exceeds the terms of the sale of products. The pronounced deficiency of virulence in Shigella Sonne is fully compensated by their high biochemical activity and reproduction rate in the infected substrate. It takes 8 to 24 hours to accumulate a dose of S. sonnei infecting adults in milk at room temperature. The reproduction of Shigella Sonne in contaminated products accumulates a thermostable endotoxin that can cause severe lesions in case of negative results of bacteriological examination of infected foods. S. sonnei is also distinguished by high antagonistic activity against saprophytic and lactic acid microflora.

An important feature of Sonne shigella is their resistance to antibacterial drugs. Outside the body, the resistance of shigella of different species is not the same. Shigella Sonne and Flexner can survive in water for a long time. When heated, shigella quickly die: at 60 ° C – within 10 minutes, when boiled – instantly. The least resistant are S.flexneri. In recent years, heat-resistant (able to survive at 59 ° C) strains of Shigella Sonne and Flexner are often isolated. Disinfectants in normal concentrations are detrimental to Shigella.


The reservoir and source of infection is a person (patient with acute or chronic form of dysentery, carrier, convalescent or transient carrier). The greatest danger is presented by patients with mild and erased forms of dysentery, especially persons of certain professions (working in the food industry and persons equated to them). From the human body, Shigella begin to stand out at the first symptoms of the disease; the duration of the discharge is 7-10 days plus the convalescence period (average 2-3 weeks). Sometimes the isolation of bacteria is delayed up to several weeks or months. The tendency to chronicize the infectious process is most characteristic of Flexner’s dysentery, and the least of Sonne’s dysentery.

The mechanism of transmission of infection is fecal-oral, the routes of transmission are water, food and contact-household. With Grigoriev-Shiga dysentery, the main route of transmission is contact-household, which ensures the transmission of highly virulent pathogens. With Flexner’s dysentery, the main route of transmission is water, with Sonne’s dysentery, food. Sonne bacteria have biological advantages over other Shigella species. Yielding to them in virulence, they are more stable in the external environment, under favorable conditions they can even multiply in milk and dairy products, which increases their danger. The predominant action of certain factors and routes of transmission determines the etiological structure of the disease with dysentery. In turn, the presence or predominance of different ways of transmission depends on the social environment, living conditions of the population. The range of Flexner’s dysentery basically corresponds to the territories where the population still consumes epidemiologically unsafe water.

The natural susceptibility of people is high. Post-infection immunity is unstable, species-specific and type-specific, repeated diseases are possible, especially with Sonne dysentery. The immunity of the population does not serve as a factor regulating the development of the epidemic process. At the same time, it has been shown that post-infection immunity is formed after Flexner’s dysentery, which can protect against recurrent disease for several years.

Main epidemiological signs. Bacterial dysentery (shigellosis) is a widespread disease. Constituting the bulk of the so-called acute intestinal infections (or diarrheal diseases, in WHO terminology), shigellosis poses a serious public health problem, especially in developing countries. The wide spread of intestinal infections in developing countries causes a miserable level of existence of people in unsanitary living conditions, customs and prejudices that contradict elementary sanitary standards, poor-quality water supply, malnutrition against the background of an extremely low level of general and sanitary culture and medical care for the population. Conflict situations of various kinds, migration processes and natural disasters also contribute to the spread of intestinal infections. The development of the epidemic process of dysentery is determined by the activity of the transmission mechanism of infectious agents, the intensity of which directly depends on social (the level of sanitary and communal improvement of settlements and the sanitary culture of the population) and natural and climatic conditions. Within the framework of a single fecal-oral transmission mechanism, the activity of individual pathways (water, household and food) in different types of shigellosis is different. According to the developed by V.I. Pokrovsky and Yu.P. Solodovnikov (1980) of the theory of etiological selectivity of the main (main) ways of transmission of shigellosis, the spread of Grigoriev-Shiga dysentery is carried out mainly by contact-household, Flexner’s dysentery – by water, Sonne’s dysentery – by food. From the standpoint of the theory of correspondence, the transmission routes become the main ones, ensuring not only wide distribution, but also the preservation of the corresponding pathogen in nature as a species. The cessation of the activity of the main transmission route ensures the attenuation of the epidemic process, which is unable to be constantly maintained only by the activity of additional routes.

Characterizing the epidemic process in shigellosis, it should be emphasized that these infections include a large group of epidemiologically independent diseases, including the so-called large (Sonne, Flexner, Newcastle, Grigoriev-Shigi shigellosis) and small (Boyd, Stutzer-Schmitz, Large shigellosis). -Saksa and others) nosological forms. Large nosological forms constantly remain widespread, the epidemiological significance of small forms is small. At the same time, it should be mentioned that over the past century, the significance of individual shigellosis in human pathology has changed. So, at the beginning of the 20th century, during the years of the civil war and intervention, famine and poor sanitary conditions, high morbidity, severe forms and mortality were associated with the spread of Grigoriev-Shiga dysentery. In the 1940s and 1950s, up to 90% of diseases were caused by Flexner’s shigella, while the second half of the century was marked by the prevalence of Sonne’s dysentery. This pattern determined the biological properties of the pathogen and socio-economic changes in human society at different stages of its development. Thus, the change in the social environment and living conditions of the population turned out to be the main regulator of the etiology of dysentery. In recent years, Grigoriev-Shiga’s dysentery has again attracted attention. Three major foci of this infection have formed in the world (Central America, Southeast Asia and Central Africa) and cases of its importation to other countries have become more frequent. However, for its rooting, certain conditions are needed that are available on the territory of the states of Central Asia. World experience indicates the possibility of the spread of shigellosis and secondary ways. Thus, large waterborne outbreaks of Grigoriev-Shiga dysentery are known, which arose in many developing countries during the late 60-80s against the background of its global spread. However, this does not change the essence of the epidemiological patterns of individual shigellosis. As the situation normalized, Grigoriev-Shiga’s dysentery again became predominantly spread in the domestic way.