The adhesive activity of diphtheritic strains in relation to the characteristics of the infectious process they induce]

The degree of adhesiveness of 602 C. diphtheriae strains isolated from patients with different forms of diphtheria was studied on trypsinized sheep red blood cells (SRBC) used as an experimental model. The titer of bacterial suspension, i.e. its highest dilution ensuring the agglutination of 50% of SRBC, was assumed to be the index of adhesive activity. The toxigenic strains were more homogeneous with respect to the degree of their activity and proved to be moderately and highly adhesive, while among the nontoxigenic strains faintly and moderately adhesive ones prevailed. The degree of adhesiveness was not linked with the cultural biological strains variants, but depended on the form of C. diphtheriae infection. The toxigenic strains isolated from diphtheria patients were essentially more active than those isolated from carriers. Both toxigenic and nontoxigenic strains isolated in cases of prolonged carrier state (more than 4 weeks) did not differ in the degree of their adhesiveness and were essentially more active than the strains isolated from short-term carriers. The strains circulating in 10 closed groups with a high proportion of pronounced cases of carrier state (70.6% to 86.7%) were essentially more active than those circulating in 10 similar groups, but having a low proportion of pronounced cases of carrier state (6.7% to 23.8%). The conclusion was made that the degree of adhesiveness proved to be an important factor of C. diphtheriae pathogenicity, responsible for the formation of carrier state. Along with pathogenicity, this factor should be taken into consideration in the evaluation of the epidemiological importance of different sources of infection.     

Characteristics of the bacterial component in the dynamics of the infectious process in experimental pseudotuberculosis]

A model of experimental pseudotuberculosis caused by the administration to albino mice of virulent local pseudotuberculosis strains was used to study migration of the causative agent into the macroorganism and its tropism. Experimental results permitted to establish a number of regularities attending bacterial spread. The infectious process in pseudotuberculosis began from invasion of the causative agent into the intestinal wall and the subsequent initial bacterial reproduction at the site of invasion and penetration from the intestine into the regional mesenteric lymph nodes. This was followed by rapid reproduction of the microbes in these nodes and contamination of all the organs. With comparatively low doses of the causative agent administered and adequate resistance of mice the infectious process could either stop at the phase of regional infection with regression, or, following hematogenic dissemination, pass into the phase of decline and terminate by animal recovery. Administration of massive doses of the virulent culture led to a septicemic process and death. Experimental data concerning the localization of the microbe in the macroorganism at various phases of the infectious process confirmed the enterotropic character of the pseudotuberculosis causative agent.     

Enterotoxic properties of salmonellae and their neurotoxins

Most of live S. typhimurium cultures are capable of intraintestinal proliferation and possess enterotoxic activity. The capacity of S. typhimurium strains for producing enterotoxins is not connected with their origin. The parenteral immunization of rabbits with corpuscular vaccines prepared from S. typhimurium induced changes in the sensitivity of different sections of the small intestine of the animals to the enterotoxic action of live homologous cultures. Neurotoxin isolated from S. typhi was found to possess enterotoxic activity.     

Cytogenetic and immunological changes in the peripheral blood of measles patients in the dynamics of the infectious process

During the acute period of disease (2-5 days after infection) and later (one month after infection) the associative index of acrocentric chromosomes in T-lymphocytes was higher than in norm, whereas two weeks after infection it did not differ from that in norm. A correlation was found between the quantity of lymphocytes, having a certain number of associated acrocentric chromosomes, the quantity of sensibilized chromosomes, and the number of antibodies. Chromosome alterations in the lymphocytes of reconvalescents were recorded more often than at the start of the illness.     

Biological properties of salmonellae and local immunity in Salmonella infection

The comparative study of the biological properties of S. enteritidis and S. typhimuruim, isolated from patients and convalescent carriers, was carried out. Factors inactivating the components of the local immunity of the intestine (lysozyme, complement, lactoferrin, IgG, IgM and IgA) were detected in the causative agents of Salmonella infections. The spread and expression degree of properties of a causative agent were serovar-depended: high penetration characteristics and the expression of anti-lactoferrin and anti-immunoglobulin activity were characteristic of S. typhimurium. S. enteritidis strains isolated from patients with carrier state formed in the convalescence period were found to have higher persistence level. In co-profiltrates obtained from carriers at the peak of the disease and during convalescence lower levels of IgM, IgG, sIgA, complement and lactoferrin were determined in comparison with those in coprofiltrates obtained from patients in whom no subsequent carrier state was formed. These results indicate that an increase in the persistence of salmonellae, occurring simultaneously with the local immunodeficiency, contributes to the prolonged survival of bacteria in the intestine.     

Capturing escape in infectious disease dynamics

Identifying the causes of interannual variability in disease dynamics is important for understanding and managing epidemics. Traditionally, these causes have been classified as intrinsic (e.g. immunity fluctuations) or extrinsic (e.g. climate forcing); ecologists determine the relative contributions of these factors by applying statistical models to time series of cases. Here we address the problem of isolating the drivers of pathogen dynamics that are influenced by antigenic evolution. Recent findings indicate that many pathogens escape immunity in a punctuated manner; for them, we argue that time series of cases alone will be insufficient to isolate causal drivers. We detail observations that can reveal the presence of punctuated immune escape, and which can be used in new statistical approaches to identify extrinsic and intrinsic regulators of disease.     

The metapopulation dynamics of an infectious disease: tuberculosis in possums

An SEI metapopulation model is developed for the spread of an infectious agent by migration. The model portrays two age classes on a number of patches connected by migration routes which are used as host animals mature. A feature of this model is that the basic reproduction ratio may be computed directly, using a scheme that separates topography, demography, and epidemiology. We also provide formulas for individual patch basic reproduction numbers and discuss their connection with the basic reproduction ratio for the system. The model is applied to the problem of spatial spread of bovine tuberculosis in a possum population. The temporal dynamics of infection are investigated for some generic networks of migration links, and the basic reproduction ratio is computed-its value is not greatly different from that for a homogeneous model. Three scenarios are considered for the control of bovine tuberculosis in possums where the spatial aspect is shown to be crucial for the design of disease management operations.     

The effect of phospholipids on the adhesive properties of bacteria]

The present work shows that choline-containing phospholipids (lysophosphatidylcholine and lyso-1-alkyl-sn-glycerophosphocholine) inhibit the adhesion of some strains: Bacterium bifidum 1, B. adolescentis MC-42, B. longum B. 379M, Staphylococcus aureus P 209 and Klebsiella pneumoniae 52. Phosphatidylcholine produces no effect on the adhesiveness of these strains, while platelet activation factor stimulates adhesiveness only in strain S. aureus 209. The stimulating or inhibiting action of phospholipids on the adhesive process of microorganisms depends on the species of bacteria and on the concentration of reagents.     

The adhesive properties of bacteria of intestinal origin]

Differences between strains of nonpathogenic Escherichia and lactobacilli, as well as some pathogenic bacteria of enteric origin (Escherichia, Shigella, Campylobacter), in their capacity to adhesion to rat enteric and colonic cells have been shown in vitro. The strains under study have been found to possess more pronounced adhesiveness with respect to colonic cells, which is indicative of their higher receptive capacity in comparison with enteric cells. In the absence of normal microflora lactobacilli and Escherichia exhibit increased adhesiveness with respect to enteric cells. Escherichia enterotoxigenic strains, Yersinia enterocolitica and Salmonella typhimurium virulent strains, Campylobacter jejuni clinical isolates possess more pronounced capacity for adhesion to enteric cells of Peyer's plaques than to other types of epithelial cells, which may be of importance in the pathogenesis of these infections.     

The phenomenon of tachyphylaxis in the pathogenesis of an experimental infectious process]

Experiments on mice have revealed that the development of experimental purulent infection is accompanied by a considerable increase in the nonspecific resistance of the animals to additional infection with unrelated bacteria (the effect of tachyphylaxis). Morphologically, this is manifested by the rapid limitation of the focus of inflammation at the site of inoculation of the superinfecting agent. The state of the phagocytic apparatus is of great importance for this phenomenon as disturbances in the macrophage activity caused by the injection of carrageenan abolish the protective effect of primary infection. The phenomenon of tachyphylaxis has been shown to play a certain role in the prevention of the septic generalization of the process and in resistance to superinfection.     

Role of apoptosis in the regulation of the infectious process

Review on the influence of pathogenic bacteria on the apoptosis program of host cells. Many pathogenic bacteria posess mechanisms to control cell death, which makes it possible to maintain the optimum conditions for the development of infection. The mechanisms of the induction and suppression of apoptosis, worked out by bacteria, are very variable and realized as the result of complex interaction of biologically active bacterial molecules with concrete targets of signal paths leading to apoptosis. In case of intracellular parasitism the antiapoptosis activity of bacteria may be regarded as one of the mechanisms of the persistence of infective agents, ensuring the development of chronic infections.     

The antimicrobial activity of nitric oxide and its role in the infectious process

In this article information on an important role of nitric oxide (NO) in inhibiting the growth of a number of pathogenic microorganisms, including intracellular parasites, and their elimination from the host body is presented. Differences between the mechanisms of the production of NO and free-radical compounds having antimicrobial action are given. The regulation of the activity of constitutive NO-synthase and inducible NO-synthase and the relationship between the latter and the phagocytic activity and production of anti-inflammatory cytokines are described. An important role of NO in the development of the nonspecific resistance of the body is mentioned.     

The adhesive and colonizing properties of Aerococcus viridans]

On the basis of experiments carried out in the course of this study the conclusion can be made that one of the mechanisms of the preventive effect of aerococci, the representatives of the indigenous microflora of the gastrointestinal tract, lies in their capacity for adhesion to and colonization of the mucous membrane, this enhancing the resistance of the enteric tract to infections. These properties of anterococci substantiate good prospects of using M-bacterin (live lyophilized aerococcal culture) for the control of enteric infections and dysbacteriosis.     

The effect of heterologous bacilli on the infectious process in anthrax in an experiment

The possibility of the survival of guinea pigs after the simultaneous administration of different doses of Bacillus anthracis virulent strain 81/1 in combination with both B. anthracis vaccine strain STI and heterologous bacilli (B. subtilis strain PAC) has been experimentally shown. On the basis of the results of these experiments suggestion has been made that the "survival phenomenon" is the process involving the lysosomal systems of polymorphonuclear and mononuclear phagocytes.     

The dynamics of detecting group-A streptococci in an infectious disease clinic]

The study revealed that the isolation rate of group A streptococci in scarlet fever patients at the time of hospitalization did not exceed 68%. The isolation rate of these streptococci was greatly influenced by antibacterial therapy carried out before hospitalization. Under clinical conditions with intensive penicillin therapy group A streptococci were eliminated from the larynx on days 3-4. In 13% of children repeated streptococcal infection was observed 0.5-3 months after discharge from hospital.     

The effect of trace elements on the infectious process in plague in an experiment

The influence of Mn, Fe, Co, Ni, Cu and Zn on experimental Yersinia pestis infection in three species of gerbils (Rhombomys opimus, Meriones meridianus, M. tamariscinus) under conditions, imitating natural biogeochemical anomalies, was studied. The addition of Co and Ni to the fodder given to the animals for the period of 2-4 weeks prior to infection aggravated the course of infection. In similar experiments Cu, Fe and Mn aggravated or, on the contrary, inhibited the development of infection, depending on the environmental conditions. The addition of Zn produced practically no effect on the course of the disease, but its use in combination with Cu, depending on the dose, inhibited or enhanced the action of this element. The addition of Cu, Fe and Mn to fodder made it possible to reproduce the effect of protection from plague, observed in nature in the presence of some biogeochemical anomalies. This result may serve as an argument in support of the concept stating that the chemical composition of the environment is a factor capable of regulating the infectious process in animals in nature.