Plasmid content in Yersinia pestis strains of different origin

Plasmid content in 242 Yersinia pestis strains from various natural plague foci of the U.S.S.R. and other countries was studied. Of these strains, 172 (71%) were shown to carry three plasmids described previously of about 6, 45-50 and 60 MDa, respectively. Twenty strains (8%) from different foci harboured additional cryptic plasmids, most often of about 20 mDa in size. Plasmid pPst displayed considerable constancy of its molecular mass. On the contrary, size variations of pCad (45-49 MDa) and, especially, pFra (60-190 MDa) were found. Molecular mass of these plasmids correlated with the host strain origin.     

Conditions and factors determining the etiological structure of dysentery and its changes. Report 1. Epidemiological theory of etiological selectivity of the main (primary) pathways of infection and their differences in various nosological forms of dysentery]

The authors present the elaborated and formed epidemiological theory ("conformity theory") according to which the etiological structure of dysentery is determined by the etiological selectivity of the main (primary) waves of transmission of the infection differing in various nosological forms of dysentery. In Grigoriev-Shiga dysentery the domestic way of the spread of infection plays the main role, in Flexner and Newcastle dysentery--the water way, and in Sonne dysentery--the food way (particularly through the milk). Evolution of the etiological structure of dysentery serves as the reflection of evolution of the principal ways of transmission. The complex of prophylactic and antiepidemic measures in individual noslogical forms of dysentery should be differentiated and be directed in epidemiological sense to the neutralization of the corresponding main (primary) way of transmission of the infection.     

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.     

Shigellosis in the USSR: the etiological role of Shigella dysenteriae

The etiological role of S. dysenteriae in Shigella infections at different territories of the USSR in 1983-1987 is analyzed. The study shows that S. dysenteriae pertain to territories with unfavorable water supply of the population. At some of these territories, in particular the Uzbek SSR, Grigor'ev-Shiga dysentery seems to gain ground and the restoration of the area of its spread occurs. In recent years the penetration of Grigor'ev-Shiga dysentery from abroad became more frequent in the presence of the pandemic of this dysentery in the world, which caused the appearance of the disease in 17 out of 27 basic territories of the All-Union Center of Shigella Infections. The ways for increasing the control of this infection are outlined.     

Spread of salmonellosis in Moscow and the ways of its prophylaxis

The article deals with the results of the epidemiological analysis of the spread of salmonellosis in Moscow. During the last 15 years the proportion of Salmonella enteritidis was about 80% and more. After salmonellosis morbidity decreased to 19.9 per 100,000 of the population (the minimum level) in 1985 its sharp rise was noted. Morbidity rate increased from 31.7 in 1987 to 55.1 per 100,000 in 1988, then to 93.9 per 100,000 of the population in 1989 (the maximum level). In the subsequent years up to 1996 a decrease in morbidity rate was observed, but in 1997-2002 morbidity rate stabilized within 29.8-35.7 per 100,000 of the population without a perceptible tendency towards decrease. The sharp increase of the etiological role of S. enteritidis which led to a wide spread of Salmonella infections was caused by the "chicken-egg" factor of their transmission. High morbidity rate among children and adults, registered all the year round, is the consequence of the constant epidemic activity of this factor.