Risk factors and transmission routes of the causative agents of campylobacteriosis in commercial poultry plants]

The study, carried out in two regions of the USSR and aimed at estimation of the contamination of products supplied by industrial poultry complexes (IPC), revealed that the contamination of these products was closely related to the Campylobacter contamination of the personnel of IPC. The causes of high Campylobacter contamination of the products of IPC at all technological stages of their production are described. The species, serovars and biovars of Campylobacter strains isolated from different sources were determined, which made it possible to carry out the specific and intraspecific differentiation of these strains.     

The glycolipids of the causative agent of tularemia]

Up to 10 glycolipids were detected in F. tularensis with the use of thin-layer chromatographic techniques. These glycolipids were slime antigens of F. tularensis membrane. Attenuated F. tularensis strains were found to have defects in their glycolipid composition: in the vaccine strain glycolipid 8 was replaced by more polar lipid 8-a; the avirulent strain had only two glycolipids, and one of them was not typical for virulent strains. Considering that glycolipids differed from entero-bacterial Vi-antigen in their physical-chemical and biological properties, the suggestion was made that the use of the symbol "Vi" to denote the surface substances of F. tularensis should be abolished.     

The taxonomic aspects of the transmission of the causative agent of Lyme disease

According to world literature data 17 species of ixodid ticks have been studied for natural infection with the Lyme disease agent. Analysis of the data on the level of the infection, transovarial and transphase transmission has shown that main biological vectors of Borrelia burgdorferi are the species of the subgenus Ixodes s. str. - I. ricinus, I. persulcatus (Eurasia), I. dammini, I. pacificus (North America). Potential vectors are I. scapularis, I. dentatus, Amblyomma americanum, Dermacentor variabilis. Single isolations were registered for I. neotomae, Haemaphysalis leporispalustris, D. occidentalis. Nonidentified spirocheta was isolated from A. americanum, D. variabilis, D. parumapertum, Rhipicephalus sanguineus. No agent was isolated from I. cookey, D. albipictus, R. reticulatus, H. concinna. On the basis of comparative and ontogenetic data the species from a group of main vectors: I. ricinus, I. persulcatus, I. pacificus had been attributed by me to the phyletic group persulcatus before Lyme disease was discovered and its causative agent isolated. The question whether I. scapularis belongs to the group persulcatus was also discussed at that time but left open due to somewhat aberrant structure of gnathosoma at preimaginal phases (Filippova, 1969, 1971, 1973). 6 Palaearctic, 2 Indomalayan and 3 Nearctic species were referred to the group persulcatus at the time. I. dammini was described later, in 1979. Gnathosoma of its preimaginal phases has an intermediate structure between I. scapularis and other species of the group persulcatus. Sexually mature phase and nymph of I. dentatus have much in common with Palaearctic members of the group, I. pavlovskyi, I. kazakstani, I. kashmicus. Preimaginal phases of I. scapularis and nymph of I. dentatus were studied by me on the collection material. Thus, it is possible to speak of the belonging of main vectors of B. burgdorferi to a common phyletic group within the subgenus Ixodes s. str. and, therefore, of common origin of ecological medium for the agent. At the same time each species of the vector is an evolutionally developed difference of ecological medium for B. burgdorferi. Roots of the group persulcatus could originate as far as in Paleocene before the land connection between North America and Europe disappeared. Conditions for the existence of recent species, however, appeared considerably later and their flourishing is dated by Pliocene. The main epidemiological role belongs now to I. ricinus, I. persulcatus, I. dammini, I. pacificus.(ABSTRACT TRUNCATED AT 400 WORDS)     

The parasitism characteristics of the causative agent of melioidosis in the host cells]

The electron microscopic study of the damaged areas of the lungs, liver, spleen and lymph nodes of guinea pigs infected with two P. pseudomallei virulent strains C-141 and 100 has revealed that this organism is a facultative intracellular parasite and exhibits tropism to reticuloendothelial cells of the body, parasitizing both in "professional" phagocytes (mononuclear, phagocytes, polymorphonuclear leukocytes) and "nonprofessional" phagocytes (capillary endotheliocytes, splenic and lymph-node reticulocytes). In the course of their intracellular development P. pseudomallei have been shown to form capsules protecting the pathogens from the unfavorable action of the protective mechanisms of the host cells.     

The interaction of the causative agent of melioidosis with the host's alveolar macrophages]

Studies were carried out on guinea pigs and albino rats, intranasally infected with P. pseudomallei C-141. The cells of bronchovesicular exudate were obtained from animals 1, 4 and 24 hours after infection. Electron microscopy was applied to study the process of interaction of the agent and alveolar macrophages. Bacteria were shown to form a capsule which permitted avoiding phagocytosis, when entering the host respiratory system. Microbes that failed to form a capsule were absorbed by macrophages and enclosed in a phagosome. Then some bacteria were destroyed by the lysosomal enzymes, the other synthesized a capsule, which protected them against the effect of phagolysosome content. There were also such microbes which escaped from a phagosome prior to fusion with lysosomes and parasitized in phagocytic cytoplasma forming a capsule there. By the end of the first 24 hours of observation the intact encapsulated microbe species were found to prevail in the host cells.     

The properties of the extracellular alkaline phosphatase of the causative agent of melioidosis]

After growing P. pseudomallei VPA on solid medium extracellular alkaline phosphatase with a molecular weight of 93,000 AMU was isolated, and practically purified from the extract of this medium by precipitation with ammonium sulfate, subsequent gel chromatography and concentration on membrane filters. The optimum conditions for enzymatic reaction were found to be pH 9.0 and a temperature of 50 degrees C. The enzyme was resistant to freezing and to heating at a temperature of up 60 degrees C for 30 minutes, as well as to the action of pH 3.0-10.5, but became completely inactivated after heating at 90 degrees C for 10 minutes and incubation at pH 2.0 for 20 hours.     

Geographical race typing of the causative agent of tularemia using antibiotics]

Reaction of the strains of the tularemia causative agent to erythromycin (100 gamma/ml) or oleandomycin (400 gamma/ml) is one of the taxonomic tests. The study of 82 strains of the holarctic race and 63 strains of the Central Asiatic race according to this test showed that the strains of the holarctic race were divided with respect to these macrolides into sensitive (biotype I) and resistant (biotype II). The strains of the both races were isolated at the territory of the Kazakh SSR. Such a reaction of the strains of the holarctic race is a stable feature and is not connected with virulence, the isolation source and the biochemical properties of the strains. Division of the holarctic race into the biotypes (I and II) with respect to erythromycin and oleandomycin may be of definite significance in epidemiological and epizootological examination for tularemia with a purpose of determining the source of the infection, as well as in defining the borders of the infection focus area with circulation of this or that biotype of the holarctic race of the tularemia causative agent.     

Problems of resistance of the causative agent of melioidosis to antibiotics]

It was shown that the pathogen causing melioidosis was highly resistant to antibiotics including beta-lactams. Antibiotic sensitive mutants of P. pseudomallei were isolated after mutagenesis induced by nitrosoguanidine. Permeability for 3H-tetracycline and tetracycline sensitivity of the mutant cells was respectively 3 and 20 times as high as those of the initial parent strain. Gas liquid chromatography revealed quantitative and qualitative changes in separate sugars of the lipopolysaccharide structure in antibiotic sensitive mutants as compared to the initial strain.     

Preservation of the causative agent of tularemia in the external environment in eastern Taimyr]

Strains of the causative agent of tularemia were for the first time isolated by the authors from the objects of the external environment in the tundra zone of Eastern Taimir; this indicates a possibility of preservation of the microbe under conditions of the extreme north.     

Crayfish population size under different routes of pathogen transmission

We present an epidemiological model for the crayfish plague, a disease caused by an invasive oomycete Aphanomyces astaci, and its general susceptible freshwater crayfish host. The pathogen shows high virulence with resulting high mortality rates in freshwater crayfishes native to Europe, Asia, Australia, and South America. The crayfish plague occurrence shows complicated dynamics due to the several types of possible infection routes, which include cannibalism and necrophagy. We explore this complexity by addressing the roles of host cannibalism and the multiple routes of transmission through (1) environment, (2) contact, (3) cannibalism, and (4) scavenging of infected carcasses. We describe a compartment model having six classes of crayfish and a pool of crayfish plague spores from a single nonevolving strain. We show that environmental transmission is the decisive factor in the development of epidemics. Compared with a pathogen-free crayfish population, the presence of the pathogen with a low environmental transmission rate, regardless of the contact transmission rate, decreases the crayfish population size with a low risk of extinction. Conversely, a high transmission rate could drive both the crayfish and pathogen populations to extinction. High contact transmission rate with a low but nonzero environmental transmission rate can have mixed outcomes from extinction to large healthy population, depending on the initial values. Scavenging and cannibalism have a relevant role only when the environmental transmission rate is low, but scavenging can destabilize the system by transmitting the pathogen from a dead to a susceptible host. To the contrary, cannibalism stabilizes the dynamics by decreasing the proportion of infected population. Our model provides a simple tool for further analysis of complex host parasite dynamics and for the general understanding of crayfish disease dynamics in the wild.     

Isolation of the causative agent of tularemia from Siberian lemmings in Eastern Taymyr]

The authors present the results of bacteriological and serological study for tularemia of 498 lemmings caught in Taimyr. Positive results were revealed in 4 out of 98 sera examined in the indirect hemagglutination test. In carrying out 67 biological tests on albino mice there were isolated for the first time in the Soviet Union 6 cultures of the causative agent of tularemia from the spleen of lemmings. By morphological, cultural and virulent properties the cultures obtained failed to differ from those isolated in other regions of the Soviet Union, and, consequently, we referred to the holoarctic race. Thus, it was established by the authors (both serologically and bacteriologically) that there existed tundra foci of tularemia.     

The epidemiological aspects of campylobacteriosis in children in arid area]

Specific epidemiological features of Campylobacter infection in children in Samarkand Province during the period of 1987-1990 are discussed. The specific proportion of this infection in the total structure of acute enteric infections was, on the average, 8.5%, and Campylobacter carriership among healthy children, 7.0%. Among children with Campylobacter infection, children aged up to 1 year constituted 71.5%. The results of the study of the biological properties of Campylobacter strains isolated from sick and healthy children and their difference from strains isolated in other regions are discussed.     

Sensitivity of different strains of the causative agent of plague to disinfectants]

Various strains of the plague microbe was found to have statistically significant differences in their sensitivity to phenol, formaldehyde and chloramine. These differences did not correlate with the origin, virulence and nutritional requirements of the plague strains. The sensitivity of the plague microbe to formaldehyde and phenol was found to be related to the permeability of its cell wall.