INFECTION (late lat. infectio infection) — implementation and reproduction of microorganisms in a macro-organism with the subsequent development of a difficult complex of their interaction — from a carriage of activators to the expressed disease.
The term «infectio» is entered by K. Gufeland in 1841, however it was applied generally at the description of venereal diseases in the beginning. The sense of the concept «infection» is insufficiently strictly defined in medical literature. So, under And. often mean disease-producing factors or an infectious disease as nozol, a form, a condition of infectiousness of an organism, the fact of implementation in an organism of the pathogenic agent, location (localization) of a microbe in an organism etc. The listed definitions which are widely applied not only in practice, but also in scientific literature, not fully reflect characterized above biol, essence of the concept «infection», a cut is not equivalent to the concept «infectious disease».
And. — the phenomenon observed among the live organisms which are at different stages of organic evolution. So, the bacteriophagia also is And., connected with penetration of a phage (its nucleinic to - you) in a bacterial cell.
The doctrine about And. considers properties of causative agents of infectious diseases and fiziol, defense reactions of a human body (animal) which define the nature of their interaction: from an asymptomatic carriage of activators to manifestly proceeding infectious disease and even death of a macroorganism. From this it follows that the main maintenance of the concept «infection» is the process developing in a macroorganism as a result of implementation in it a pathogenic microbe i.e. infectious process. The creating influence on process of interaction micro and macroorganisms and, naturally, on its wedge, manifestations render conditions of the environment in which it proceeds. In relation to the person, unlike animals, conditions of the environment first of all are considered as social conditions.
Evolution of the relations between pathogenic microbes and high-organized animals among which there were also ancestors of the person proceeded directionally. So, along with increase biol, activities and resistance of separate strains of this or that species of microorganisms to defensors of a macroorganism there was a constant selection of individuals in populations of the animals more successfully resisting to action of aggressive factors of microorganisms. It in the course of long evolutionary development also led as to improvement of system of specific and nonspecific immune responses from a macroorganism, and the device of defensors and reactions at this species of microbes. The last also caused its formation as pathogenic for the person (animal).
Initial (starting) phase of the infection defining development of the subsequent to it of various forms of interaction between micro and macroorganism, implementation of pathogenic parasites in internal environment of a human body (animal) is.
In particular, the sequence and coherence of cellular and humoral reactions of an organism in reply and and influence of alien (heterological) antigens in the course of formation of immunity is established. At the same time at various infectious diseases so difficult mechanism of formation of specific immunity is rather stereotypic. Therefore, the mechanism of implementation various on biol, to properties of pathogenic parasites in a macroorganism though it and is provided with a big set of the devices allowing to overcome external (skin and mucous covers) and internal (normal antibodies, phagocytes, a complement, interferon etc.) shall be not less universal also protective barriers of an organism from contagiums. So, despite essential distinctions in a complex of reactions of an organism to implementation of the causative agents of flu, smallpox, measles, same on the mechanism of transfer, or epid, parotitis, the corresponding viruses shall have the general for them the devices providing their passing through a mucous membrane of upper respiratory tracts, achievement and penetration into cells of fabrics and bodies where they vegetirut.
Genetic researches showed that for development And. the descended polymorphism of antigenic properties of different cellular and fabric structures of an organism is important eurysynusic among people and different types of the highest animals genetically caused and, therefore, (blood groups, proteins of plasma, antigens of fabrics, etc.). Existence of almost infinite number of systems of the balanced hereditary polymorphism is characteristic of the person and the highest animals.
In special literature the provision that specific immunity, apparently, forms at molecular level is discussed: the microbe, its enzymes, endo-and exotoxins or do not find in a macroorganism of the corresponding so-called substrate receptor molecules at all, or meet the molecules blocking their activity.
Existence of these or those antigenic features of a structure of fabrics in the higher organism, obviously, can be considered among the factors defining emergence and I. Predpolagayut's development that availability of the general antigens at the person (or a high-organized animal) and a pathogenic microbe promotes developing of an infectious disease since at the same time immune responses of a microorganism are weakened. E.g., antigen A of the AB0 system of blood of the person has the general structure with antigens of a virus of natural smallpox, and O-antigen — with antigens of a stick of plague.
the Doctrine about And. has long history of development: from vitalistic interpretation of essence of this process to materialistic. Antiquities
the opinion on miazmatichesky causality of infectious diseases would be eurysynusic, the infectious nature of «general» diseases was denied. For the first time the thought of the live causative agent of an infectious disease occurs at the Roman writers. So, in 1 century BC Terentsy Varron in the treatise «About the Nature of Things» emphasized wildlife of «the sticking beginning». The term «contagium vivum» occurs at A. Kircher who in 1659 called so causative agents of plague (in his opinion, small worms).
In the Middle Ages when often there were cruel epidemics owing to considerable accumulation of people in limited territories as a result of an urbanization, conviction in existence of causative agents of infectious diseases took roots finally. Rather accurately original positions of the kontagionistsky doctrine were formulated in 16 century by the ital. doctor D. Frakastoro who specified a pas the next ways of spread of infectious diseases: through contact, by means of various objects, at distance, through air. At this D. Frakastoro not only suggested about wildlife of a contagion, but for the first time discussed a problem of specificity of the activator. D. Frakastoro was a pronounced kontagionist, but his views quite often intertwined with representations of the miazmatichesky direction.
Only at the end of 16 century by means of the magnifying lenses made by A. Levenguk there was a technical basis for opening of microbes. It was a starting point of development of the so-called morphological period in microbiology. L. Pasteur laid the foundation for studying of physiology and biochemistry of microbes (to the physiological period in microbiology), to clarification of a role of microbes in the nature and in life of mankind. On the basis of its works the doctrine about And. gained further development. At the end of 19 century it was proved that infectious diseases, are caused by microorganisms not only vegetable, but also animal origin.
The classical pathology and immunology created by R. Virkhov, R. Koch, P. Ehrlich, etc. exerted exclusive impact on understanding of essence And. also recognized as the only origin of epidemics microorganisms. At the same time in the beginning development of a disease in the person or an animal rather fondly was explained by pressure of the breeding pathogenic microbes upon cells of Pi starvation of the last." Then a nek-swarm time the view of effect of toxins of microorganisms as the main reason for a course of a disease dominated.
I. I. Mechnikov was the first researcher who experimentally and theoretically established a role of a makroooganizm in I. V the subsequent his pupil G. N. Gabrichevsky also repeatedly pointed to the leading role of a macroorganism in emergence and development of infectious process. At all its forms I. from materialistic positions can be considered as interaction micro and a macroorganism in the conditions of the environment. And features of this interaction define the main peculiar and individual traits of infectious process and the possibility of its emergence.
Modern views on And. developed under the influence of materialistic philosophy. K. A. Timiryazev and other researchers developed the doctrine about unity of an organism and Wednesday. I. P. Pavlov formulated the main patterns of relationship of an organism with the environment, one of factors a cut are microorganisms (so-called extraordinary irritants). Significant contribution to studying And. D. K. Zabolotny brought.
Its works on an etiology and a pathogeny of a number of infectious diseases (1956 — 1957) are classical. P.F. Zdrodovsky's researches, L. A. Zilbera expanded ideas of specific reactive factors of an organism. L. V. Gromashevsky created the doctrine about mechanisms of transfer And. Besides, the doctrine about And. domestic pathologists, parasitologists, microbiologists and immunologists developed: A. I. Abrikosov, N. F. Gamaley, I. V. Davydovsky, E. I. Martsinovsky, E. N. Pavlovsky, I. G. Savchenko, A. D. Speransky, L. A. Tarasevich, etc.
the ROLE of MICROORGANISMS IN DEVELOPMENT of the INFECTION
Causative agents of infectious diseases are microorganisms of plant and animal origin: bacteria, spirochetes, the lowest fungi, protozoa, viruses and rickettsiae.
Pathogenic microorganisms came from the saprophytes which adapted in the course of long evolutionary development to parasitic type of food in various fabrics and bodies of an animal organism (see. Parasitism , Parasites , Parasitic system ).
In the course of adaptation to living conditions a number of microbes gained ability to affect only a human body (see. Antroponoza ) or certain animal species (see. Zoonoza ), from which at a number of diseases also the person can catch. However many pathogenic microorganisms adapted to parasitizing in an organism of many animal species (e.g., causative agents of plague, a tularemia, rage, leptospirosis, etc.). Ability to parasitizing in an organism of the owner is caused limited, and is frequent also specific fitness to dwelling in certain bodies or fabrics of its organism (organotropy, or fabric tropism). So, the causative agent of trachoma parasitizes on a mucous membrane of an eye, the causative agent of whooping cough — in a mucous membrane of respiratory tracts (a trachea, bronchial tubes); cholera vibrio — in intestines etc. Hit of a pathogenic microbe in an organism, but not that Wednesday, to a cut it is adapted, is not followed by development of typically proceeding infectious process. E.g., for the purpose of immunoprevention of cholera live, cholera vibrioes were used; hypodermic introduction to their large number of people was not followed by development of a symptom complex, typical for this disease.
Ability of microorganisms to get accustomed in body tissues, to breed in it and to cause patol. changes is called pathogenicity (see) it is also subject to big fluctuations in various conditions. Degree of pathogenesity of a pathogenic microbe is called virulence (see).
If pathogenicity of a microorganism — its constant species character, then virulence is highly dynamic individual property of this strain of a microbe. About virulence of pathogenic microbes under natural conditions judge by weight and an outcome of the disease caused by them, in laboratory — in size of the dose causing death or development of infectious process in experimental animals. Degree of virulence is measured by conditionally accepted units — the infecting dose and the lethal dose defined in an experiment. The infecting dose (ID 50 ) — the quantity of microorganisms, a cut causes development of infectious process in 50% of the infected animals. The dose causing death of 50% of animals — a lethal dose (LD 50 ).
The most essential factors defining virulence are specific components of a cellular surface of pathogenic microbes among which the important place is taken by capsules. The microorganisms forming capsules (the activator of a malignant anthrax, a pneumococcus, etc.), as a rule, cause more hard proceeding disease, than their acapsular options. Are of great importance for virulence of bacteria about l ochechny (To) the antigens located on a surface of a cell. According to numerous experiments, carry «antigen of virulence» to them — Vi-antigen (see), received such name because the cultures supporting him were more virulent and steady against phagocytosis, than the cultures deprived of this antigen. Superficial structures of microorganisms are the main carriers of the antigenic properties defining their specificity; education and accumulation of specific antibodies in the infected organism, formation of the phenomena immunol, paralysis, the general and local allergy are connected with them. Distinctions in virulence of the activator are connected with distinctions in a combination of a number of genetically caused factors most of which is controlled by episomes or plasmids (extra chromosomal factors of heredity — ekstrakhromosomny DNA). Episomes (plasmid) can be transferred from a cell to a cell, and irrespective of other cellular genome. It creates huge advantage in selection of the factors knowing pathogenicity in the presence of the genes controlling their synthesis in an episome, but not in bacterial chromosomes. The fact of a possibility of transfer of extra chromosomal factors of heredity of pathogenic microbes to saprophytes determined by a large number of special observations speaks about quite admissible theoretical possibility of formation from among saprophytes of individuals, pathogenic for the person.
Pathogenicity of microbes is connected from them invasiveness (see). Invasiveness is understood as ability of microbes to get under natural conditions infections through integuments and mucous membranes, and also in bodies and fabrics, to breed in them and to resist to protective forces of an organism. This property of microbes is associated also with a concept about their aggression. It is established that invasiveness is connected with certain superficial structures — capsules, surface antigens, flagellums protecting microbes from phagocytes and action of antibacterial factors of blood serum and also with features of the metabolism causing ability of microbes to survive at change of conditions of internal environment of the struck macroorganism.
A number of pathogenic microbes possesses mechanisms of overcoming natural barriers. At the same time, according to L. V. Gromashevsky (1965), a part is played by the device providing mobility of parasites.
One of ways of overcoming by microbes of an epithelial barrier of mucous membranes is the so-called chreskletochny way. E.g., the possibility of transfer of microbes through mucous membranes is described by phagocytes then they are implemented into cells of bodies and fabrics. It is known that implementation of viruses in cells is preceded by a phase of adsorption of viruses a cell and allocation by viruses of so-called entrance enzymes. At an influenza virus — it is a neuraminidase, edges, working on mukoproteid cell membranes, chips off neuraminic to - that that does this mukoproteid permeable for a virus particle; parainfluenza viruses have still the second enzyme destroying a cell wall.
The products of the fermental nature developed by microbes are of great importance for overcoming protective barriers of connecting fabric. So, streptococci, causative agents of gas gangrene (mephitic gangrene) and many other types of pathogenic bacteriums develop hyaluronidase (see), destroying hyaluronic to - that is the main intercellular substance of connecting fabric that promotes penetration of microbes into depth of body tissues. Are close to hyaluronidase of a neuraminidase, mucinase, allocated by a cholera vibrio, shigellas, an influenza virus etc.
It is established also that these enzymes strengthen effect of bacterial and virus toxins, than burden the course of an infection and intoxication.
It is possible to carry to the substances increasing virulence of bacteria and, in particular, their invasive ability also fibrinolysin. This enzyme turns plasmogene of blood into proteolytic enzyme which dissolves clots of the turned fibrin which is formed in the course of an inflammation and interfering advance of microbes in depth of bodies and fabrics. Fibrinolysin streptococci, staphylococcus form, causative agents of plague and other microorganisms. The enzyme a collagenase produced by activators mephitic gangrene (see), also plays a part in ensuring invasive properties of microorganisms. Under the influence of a collagenase the intensive fusion of muscular tissue connected with destruction of fabric proteins, collagenic structures that, undoubtedly, promotes distribution of microbes on an organism is observed. The decrease in viscosity of liquids of an organism and its fabrics promoting distribution of microbes is defined also by enzymes, napr, the deoxyribonuclease depolymerizing deoxyribonucleic to - that.
Also endotoxins have pathogenic effect ekzo-. The majority developing patol, symptoms (up to death of the struck organism) is connected with their action. The products of exchange of microbic cells allocated to the environment — exotoxins have the dominating value in a pathogeny of diphtheria, tetanus, botulism, wound fevers. Bacterial exotoxins have sharp selectivity of action that causes specifics a wedge, manifestations. So, diphtheritic toxin affects a muscle of heart, a liver, kidneys, adrenal glands, increases reflex irritability of spinal ganglions. Toxin of botulism selectively affects peripheral cholinergic nerve terminations. Tetanins affect neurons of a spinal cord (tetanospasmins) and cause hemolysis of erythrocytes (tetanohemolysin). Hemolysins of a streptococcus and staphylococcus dissolve erythrocytes, and leukocidins of the same bacteria damage only leukocytes. Endotoxins are stronger connected with a body of a microbic cell and collect in a large number preferential after their death and disintegration (lysis), having the general, less specific effect on an organism (see. Toxaemia ). Action of identical amounts of endotoxins millions of times is less expressed, than effect of exotoxins. Endotoxins are emitted preferential at destruction of causative agents of a typhoid, paratyphus, dysentery, gonorrhoeas, a spotted fever, etc. Some microbes along with endotoxic action have ability to produce at the same time and exotoxins, napr, a cholera vibrio. Despite independence of each of the listed factors, pathogenic action of microbes on an organism of the person (animal) infected with them it is shown in a complex. So, toxicants like hyaluronidase can participate in process of implementation both primary invasion of the activator (infektivnost), and its reproduction and distribution on an organism (invazionnost), and factors stimulating reproduction of microbes will increase their toxic effect in connection with accumulation of toxin in an organism.
The MACROORGANISM AND the INFECTION
For fight against causative agents of infections a human body (animal) will mobilize all complex hereditarily (specific) and individually acquired mechanisms and devices interfering penetration and reproduction in its internal environment of pathogenic microorganisms received and to effect of the substances emitted by them. So, skin is impenetrable for the majority of microbes. However it is not only a mechanical barrier, but also has bactericidal properties (see. Bacterial action ), causing death of the microbes which got on its surface. Bactericidal properties of skin are caused by contents in separated sweat and sebaceous glands milk and fat to - t.
Mucous membranes are also an outside protective barrier of a macroorganism, and and in this case protective function is not only mechanical. E.g., reproduction of microbes in a stomach is interfered by high acidity and the expressed euzymatic activity of a gastric juice, and also bacterial action of the saliva and bile getting here. Bactericidal action of mucous membranes is connected also with existence in their separated special substance — lysozyme (see) which contains in the lacrimal liquid, a phlegm, saliva, peritoneal liquid, plasma and blood serum, leukocytes, in a cartilage, in women's milk. In the highest concentration the lysozyme contains in the lacrimal liquid and a cartilage.
A powerful factor of natural resistance to various viruses is the interferon produced by the cells struck with them.
An important role in overcoming ability of microorganisms to get through mucous membranes is played immunoglobulins (see), constantly present at these or those quantities in saliva and intestinal juice, etc. Being adsorbed on bacteria and viruses with formation of coarse and immobilny antigen — complexes an antibody, immunoglobulins thereby interfere with an invasion of microorganisms.
It is necessary to carry microflora to one of the factors which are constantly influencing processes of permeability of mucous membranes as it is regular, and accidentally present at pneumatic ways and a digestive tract. It is known that lactobacilli, actinomycetes, fuzobakteriya and other microbes and products of their life activity interfere with survival of the pathogenic microbes which got to an organism.
A considerable part of the main substance of connecting fabric contains polysaccharide — hyaluronic to - that, edges are raised by resistance of fabric to penetration of various foreign substances, including and pathogenic microbes. The huge role in ensuring protection of an organism belongs to cells of a mesodermal origin — to the phagocytes absorbing and digesting microbes. Microphages (granular leucocytes of blood, lymphocytes) and macrophages treat them (monocytes, histiocytes, pulpar cells, marrow, limf, fabrics, an endothelium of blood vessels). Process phagocytosis (see), for the first time, comprehensively studied it is also estimated-. ny I. I. Mechnikov, formed a basis for creation of the doctrine about immunity.
It is established that even if pathogenic microflora and gets to a macroorganism, infectious process develops not always since a state it susceptibilities (see) is one of the major factors defining a possibility of manifestation of pathogenic action of a microbe.
Along with the phenomena of specific immunity of a macroorganism the great influence on development of infectious process is rendered also by its so-called infectious sensitivity. So, some animal species (water rats, hares, house mice, hamsters, etc.) are susceptible and highly sensitive to a tularemia: they get sick and perish from the minimum doses of its activators. Unlike them gophers, groundhogs, hedgehogs, field mice and other animals, though are susceptible to a tularemia, but are much less sensitive to it: they though get sick after infection with small doses of activators, but do not perish. There is also the third group of animals (cats, foxes, polecats, etc.), not enough susceptible and almost not sensitive to a tularemia at which and at infection with massive doses of activators the disease can proceed easily and quickly terminate in recovery.
Emergence And. and features a wedge, manifestations and courses of infectious process depend on the general fiziol, reactivity of a macroorganism, on its ability to enter interaction with microorganisms, to counteract microbes activators. Also character of food, overfatigue, a sex, age and so forth belong to number of the factors influencing reactivity of a macroorganism.
Disturbance of food can exert adverse impact on any mechanism which in usual conditions of life activity of an organism interferes with reproduction and distribution of pathogenic microbes in its internal environment. Many types of insufficiency of food, including proteinaceous and triptofanovy, and also a vitamin deficiency — Retinolum, calciferols, ascorbic to - you, thiamin, Riboflavinum, Niacinum, a pyridoxine, pantothenic to - you, folic to - you, cyanocobalamine, etc. (see. Vitamin deficiency , Vitamins ) inhibit process of antibody formation and, therefore, reduce resistance to And. At heavy proteinaceous insufficiency and insufficiency folic to - you are sharply oppressed phagocytal reaction and activity of phagocytes. At alimentary insufficiency there are patol, changes weakening barrier function of the unimpaired integuments and mucous membranes: change of composition of interstitial substance; decrease or complete cessation of secretion of slime, increase in permeability of mucous membranes of intestines, and also other mucous membranes, the accumulation of a cellular detritis and slime creating a favorable environment for reproduction of activators, keratinizations and a metaplasia of a superficial epithelium, loss of a ciliary epithelium of respiratory tracts, the alimentary hypostasis resulting in the increased water content in fabrics, decrease fibroblastichesky! reactions, disturbance of process of an angenesis. The disturbance of integrity of fabrics arising at insufficiency of Retinolum and ascorbic to - you, as a rule, is followed by decrease in resistance of an organism. It is known that riboflavinovy and tiaminovy insufficiency promotes penetration of bacteria through a mucous membrane of intestines.
Character of a susceptibility to And. depends also on age and a floor. It is known that children up to 6 months are unreceptive to measles, diphtheria, etc. that is connected with passive transfer of specific antibodies from mother to a fruit in embryonal (through a placenta) and post-natal (during the feeding by breast milk) the periods, and are highly susceptible to the diseases caused by enteropathogenic strains of colibacilli or shigellas. Especially striking facts testimonial of jump of a susceptibility depending on age, are received during the studying of oncogenic viruses. It is established that are susceptible to a virus of a breast cancer only mice of certain lines are not more senior 2 — 3-not-efficient age. The virus which got to an organism of a mouse at later age gets accustomed, but does not lead to development of a tumor.
During periods, pregnancy and childbirth the female body is especially susceptible to causative agents of tuberculosis, streptococcal and staphylococcal infections.
Connect easing of phagocytal activity of leukocytes with overfatigue that also leads to decrease resistance of an organism (see).
Especially sharply influence of exhaustion in an incubation interval or at the beginning of a disease affects. Physical and mental injuries too quite often serve as the reason of decrease in body resistance. Hron, a drunkenness is followed by decrease in stability to a nek-eye to infectious diseases and promotes their heavier current. In formation of individual reactivity of an organism the significant role is played by the phenomena of genetic polymorphism. It is established, e.g., that genetically determined and, therefore, the descended availability of normal polypeptide of a chain (3 hemoglobin the susceptibility to malaria defines, and its absence — resistance to a plasmodium. It is established also that persons with a blood group of A and AB by 2,5 times more often than persons with a blood group About and In, hard react to introduction of a variolovaccine, at them the disease of smallpox proceeds heavier and more often there comes death. On the contrary, more intense postvaccinal immunity forms at persons with a blood group more often About and V. Chastota was much higher than a typroid carriage at persons with a blood group And, than among persons with other blood group. It is explained by a community of Vi-antigen of typroid microbes and antigen A of erythrocytes of the person. Due to stated the hypothesis is also formulated, according to a cut in the presence of the general antigens at the person and a microbe activator expressiveness of reactions of immunity significantly decreases. A powerful selective factor, creating hereditary polymorphism, microorganisms are. Earlier immunity of the person to a number of infectious diseases, and including to infectious diseases of animals, was connected, in particular, with inability of the corresponding microorganisms to get through mucous membranes and integuments. It is established that such microorganisms are capable to be implemented into a macroorganism, and in large quantities, at constantly available microtraumas of skin and mucous membranes. However they cannot breed because of the absence of necessary biochemical, Wednesdays, the structure a cut is controlled by genes.
The provided data confirm essential value reactivity of an organism (see) in emergence I. Tak, long since there was an idea that the expressed wedge, polymorphism such monoetiol. diseases, as, e.g., meningococcal and streptococcal infections — a consequence of distinctions in biol, features of their activators. However along with it it is not excluded that in many respects essential distinctions in a wedge, manifestations of process of interaction of streptococci and meningokokk decide on the organism struck with them by features of its individual reactivity.
INFLUENCE of the ENVIRONMENT ON CAUSATIVE AGENTS of INFECTIOUS DISEASES AND REACTIVITY of the MACROORGANISM
Development and an outcome And. from the moment of infection before completion of infectious process in many respects are defined by conditions of the environment, in a cut there is an interaction of a microbe to a susceptible organism.
Pathogenic microbes in the course of evolution adapted to existence in an organism of the main owner, being for them the habitat. However the organism infected with them as a result of development immunity (see) it is most often exempted from microbes. Therefore for preservation at the level of a look microbes shall pass from one organism occupied by them into another that also this or that term of stay in it (is impossible without their hit to the environment (including an organism of carriers) see. Mechanism of transmission of infection ).
Disease-producing microbes, being brought to the environment out of an organism of the sick person or the carrier with secrets, excretes, a fabric detritis from the centers of an inflammation, etc., get to various conditions which owing to the parasitic nature of microorganisms always in a varying degree act on them adversely. Therefore the pathogenic microorganisms especially incapable of sporogenesis, through this or that time slice inevitably shall die. Duration of their survival in the environment depends on degree of resistance to adverse action various physical., chemical and biol, factors of the environment, and also from features of biology and a structure of the microbes defining their resistance to action of these factors.
One of the major physical. factors ambient temperature is. At an optimum temperature (35 — 39 °) that corresponds to the body temperature of the person or hematothermal animals, life activity of pathogenic microbes is most intensive. At approach to extreme (extreme) minimum and maximum values of temperature processes of life activity of microbes die away. Upon transition out of extreme temperature limits their life activity stops that is followed by death or transition to an anabiotic state (disputes). Sporogenesis at bacilli happens at their hit in unfavorable conditions of the environment and is means of preservation of a look in conditions under which reproduction is impossible. At the same time spore-forming ability is inherent in not all microorganisms, pathogenic for the person.
While life activity of vegetative forms stops and they perish, disputes (the based stages) are especially steady against unfavorable conditions. So, the vast majority of pathogenic microbes has vegetative forms, as well as all nesporo-nosny bacteria, perish usually at t ° 50 — 70 ° in 5 — 10 min., and at 100 ° — is instant. Disputes have much bigger stability. E.g., disputes of an anthracic stick transfer boiling within 45 — 60 min., and disputes of causative agents of tetanus, botulism maintain effect of fluid steam (100 °) to the 3rd hour. Only heating under the pressure of 2 atm (121 °) within 30 min., as a rule, kills also high-steady disputes.
Perniciously drying, however, as well as to other adverse effects of the environment works on microbes, disputes are steadier against drying, than vegetative forms of microorganisms. Direct sunshine kill the majority of bacteria in several hours. The tubercular stick, e.g., for months remaining in the dried phlegm of patients, perishes under beams of the sun within several hours.
Microbes are much less sensitive to low temperatures, than to high. Even in liquid hydrogen, practically at — 253 °, many bacteria keep viability during the long period.
Many chemical connections possess the expressed bactericidal action; e.g., such widely common disinfecting substances as corrosive sublimate, phenol or carbolic to - that, formaldehyde, chlorine, alcohol, acids, alkalis and some other connections. However disputes of bacteria in comparison with vegetative forms highly rezistentna to chemical poisons (see. Desinfectants ).
Among biol, the factors influencing life activity of microbes first of all it should be noted action of microbes at each other. The disease-producing microbes getting with allocations of the person infected with them or an animal to the soil, water not can is long to coexist with the numerous intensively breeding saprophytes and rather quickly perish. The phenomenon biol, the competition (see. Antagonism of microbes ) generally also provides processes of so-called self-cleaning of the environment.
In researches on model of a keratoconjunctivitis at Guinea pigs at simultaneous introduction to a conjunctiva of an eye of obviously virulent dysenteric strain and one of strains E. coli is established oppression of an experimental infection up to impossibility of its reproduction.
In addition to trans-species microbic antagonism, also intraspecific antagonism is of great importance. So, during the studying of the associated action virulent and and virulent strains of shigellas it is established that avirulent strains suppressed an invasion not only a virulent parent strain of the same antigenic structure, but also other dysenteric strains.
To number powerful biol, the factors which are perniciously operating on pathogenic microorganisms belongs also bacteriophage (see), influencing microbes not only in the organism struck with them, but, probably, more during their stay in the environment. Were long since undertaken attempt to use drugs from so-called virulent phages as agents of sterilization of various objects of the environment contaminated by pathogenic microbes, in particular numerous representatives of intestinal group.
The environment exerts impact and on resistance of a macro-organism. L. Pasteur's experience which proved a possibility of infection of a chicken with a malignant anthrax at fall of temperature of his body immersion of extremities in a cold water served as a starting point for numerous works by means of which it is established that body temperature significantly influences reactivity of a macroorganism. So, in an experiment it is possible to overcome even mechanisms of specific immunity and to infect frogs with a stick of a malignant anthrax, and lizards — plague microbes if to support these animals respectively at 35 ° and 26 °. The susceptibility of hens to a malignant anthrax can achieve not only immersion of their extremities in a cold water, but also febrifugal medicines. P.F. Zdrodovsky (1929) observed deadly enterita at the Guinea pigs and rabbits who were exposed to overheating. Armstrong (S. Armstrong, 1950), having noted communication between an absolute humidity and incidence of poliomyelitis, came to conclusion that the increased air humidity increases a susceptibility of an organism owing to decrease in baryerfiksiruyushchy function of tissues of nasopharynx.
Seasonal rises in incidence of various infectious diseases of respiratory tracts most defiantly illustrate temperature effect and humidity of the environment on a susceptibility to infectious diseases. The low temperature and high relative humidity which are observed during the autumn and winter period adversely affect reactivity of a macroorganism and, in particular, a condition of a nasopharynx that is followed by the raised susceptibility to various causative agents of acute diseases of upper respiratory tracts.
By numerous researches it is established that temperature effect on resilience a macro-shouting of hashish is in many respects connected with decrease of the activity of phagocytal reaction.
A. L. Chizhevsky's works (1965) established connection between activity of space factors and a developmental character of epidemics. In his opinion, numerous functional and organic disturbances in life activity and development biol, systems are a consequence of a complex of electromagnetic indignations in the environment which cornerstone physical are. processes in the sun. The numerous materials testimonial of influence of space factors on function of cardiovascular system and psychological activity of an organism of people and animals are published. There are bases to allow existence of a feedforward between solar activity and a susceptibility of a human body (animal) to pathogenic microbes.
Connect with changes of solar activity also the phenomena biol, a rhythm — change of functional activity of organisms within terrestrial days. Seasonal and daily fluctuations in a condition of a susceptibility (immunity) of a human body to pathogenic microbes are not excluded.
FORMS of DISPLAY of the INFECTION
High specificity of action of pathogenic microbes on a macroorganism owing to specific features of their exchange and products of biologically active metabolites, distinction in virulence of strains, the size of the infecting dose, a state immunol. reactivity of the person (animal) at the time of infection and character of conditions of the environment in which it occurs make that complex of factors which various combination causes variety of forms of infectious process. Therefore infection with the same activator in one cases is followed by development is clinically expressed to the proceeding disease with a symptom complex, typical for it (see. Infectious diseases ), in others — only formation of an asymptomatic carriage (see. Carriage of contagiums ).
In process of development and use highly sensitive laboratornoinstrumentalny and immunol, methods of a research it is established that in an organism of so-called healthy carriers in the absence of the expressed disturbances in the state of health come to light typical for the corresponding disease funkts, and morfol. changes. At the same time the quantitative characteristic of the last is so small that they are not followed by clinically expressed displays of a disease. Therefore, about a healthy carriage the clinical, but not pathogenetic sense knows more. The essence of a concept about inaparantny also testifies to legitimacy of such interpretation of a healthy carriage And. (proceeding it is hidden, without external symptoms), (1925) formulated by Sh. Nikoll on the basis of studying of an experimental sapropyra at Guinea pigs.
In case of infection with two and more activators from among representatives of different types of microbes development of multi-infection is possible. Wedge, manifestation of the last is peculiar since it is not expressed by the sum of the symptoms characteristic of each of the diseases making it. Emergence secondary And. it is connected with accession to a basic disease of other infectious disease caused by often opportunistic microbes. So, secondary staphylococcal or pneumococcal And. quite often joins flu, measles, diphtheria etc.
At some infectious diseases the disease proceeds, as a rule, with manifestation of accurately expressed symptoms (smallpox, plague, measles, etc.) whereas for a number of infectious diseases (diphtheria, flu, scarlet fever, etc.) a large number of the erased and asymptomatic forms is characteristic. In these cases because of insufficiently expressed symptomatology the diagnosis and, therefore, early detection and isolation of patients — sources of contagiums is complicated.
It is known that formation of a massive immune layer among the population against the background of epid, wellbeing also is a consequence of a wide spread occurance of an asymptomatic carriage. The ratio of asymptomatic and manifest forms of infectious process characterizes degree of resistance of the person to them: the more often infectious process is shown in the latent form, the organism is less susceptible. It is known that the phenomenon of recurrence of level of spread of infectious diseases — alternation in time of rises and recessions of incidence by them is connected with the size of an immune layer also. Believe that asymptomatic forms often develop at reinfections (see), i.e. repeated infection after the postponed disease.
Understand infection of the patient with an additional dose of the activator which caused a disease in the conditions of unfinished infectious process as superinfection. Significantly without influencing character of a course of sharply proceeding infectious diseases, superinfection can aggravate hron, processes (e.g., the course of tuberculosis).
From asymptomatic And. latent differs — it is hidden proceeding And., characteristic for hron, diseases, with typical change of the periods (phases) a wedge, manifestations the periods a wedge, wellbeing — remissions (syphilis, malaria). Therefore without knowledge of the anamnesis inspection of the patient during remission can lead to wrong representation about his health. Serious value latent And. in epidemiology is confirmed by a large number of messages on a wide spread occurance of various so-called latent viruses. It is known that the activator of a herpes infection it is long it is hidden exists in an organism, showing pathogenetic action only against the background of decrease in reactivity owing to overcooling, a disease, the increased insolation, periods, emotional shocks, etc.
The concept which is found in literature on the mute and dozing infection is closely connected with a concept about latent infection, cover discussion of essence inseparably from so-called endogenous And. or autoinfections (see). In turn the concept about autoinfection is associated with a concept of fr. authors about microbes de sortie (the microbes ready to an exit). However if first of all connect generalization and acute disease with the dozing infection, napr, the streptococcal sepsis caused by the pathogenic streptococci which are earlier localized in almonds or on wound surfaces, then actually autoinfection contacts the microbes commensals which are constantly living in an organism (e.g., a colisepsis, a colienteritis). The majority epidemic extending And. are exogenous; diseases arise in these cases at infection with the microbes getting to an organism from the environment.
The EXPERIMENTAL INFECTION
the Main method of studying of infectious process is a complex research of functions of bodies and systems of sick people during development, currents and permissions of an infectious disease.
During the carrying out these researches are used fiziol., gistol., biochemical, gematol., mikrobiol., immunol., tool and other techniques and receptions.
Along with it the valuable data for clarification of a number of aspects of a pathogeny and immunity is received as a result of infection and a research of experimental animals. The main objectives of experimental reproduction of an infection at animals are: interpretation of origins of infectious process; studying of ways of implementation and distribution of activators in an organism, and also the factors defining their specific localization; studying of specifics fiziol. and morfol, changes of fabrics and bodies in the course of reproduction of microbes and action of their biologically active metabolites (toxins and enzymes); studying of features of formation of immunity (duration and tension) and its character (cellular, humoral); clarification of the mechanism of action pharmakol, and biol, drugs for the purpose of the choice of the most effective to lay down. and prophylactics.
At experimental reproduction of infectious diseases of the person the great value gets the choice of a species of laboratory animals and methods of their infection. Infectious process is characterized by a cycling current, and its experimental reproduction at animals shall be followed more or less expressed a wedge. - fiziol. the symptoms and anatomic defeats characteristic of the modelled infection. The model of an experimental infection in the pathogenetic relation shall recreate a picture of defeats, the closest to the corresponding disease of the person and be characterized by high reproducibility of results at infection of animals of this look, weight and a floor. Such modeling not always is successful. At animals in the kliniko-functional and anatomic plan the disease reminding the corresponding suffering of the person quite often develops. So, the paratyphoid infection of the mice, rats, rabbits and monkeys infected enterally has rather expressed looking alike typhus forms of salmonelloses of the person. Rabbits, Guinea pigs easily get sick at experimental infection with causative agents of a typhus, a malignant anthrax and tuberculosis. Naturally, at animals a row successfully is reproduced zoonoz (see), dangerous to the person (plague, tularemia, leptospirosis, listeriosis, brucellosis). However much more often at animals it is possible to cause only separate phase manifestations a wedge, and morfol, the pictures typical for infectious process in the person, or their various combinations. Therefore about a pathogeny of a disease are often applied to a better understanding as various methods of introduction of its activator by an animal of one look, and infection of the laboratory animals belonging to several types. E.g., during the modeling of a shigellezny infection Guinea pigs, cats, mice and rabbits are used. Infection is carried out on mucous membranes of a conjunctiva, a bladder, enterally, intranazalno or in loops of guts. biol, monkeys who get sick not only at enteral experimental infection are recognized natural model, but also it is spontaneous in the conditions of bondage.
By search of ways of creation of models of an experimental infection the great value belongs to studying of so-called spontaneous and negative models. Spontaneous models of some diseases of the person are chosen from among known in interdisciplinary sciences — zoology, biology, veterinary science. So, dysentery at bears, salmonellosises and flu at pigs, hron, a pyocyanic infection of urinogenital ways at bulls, hron, tuberculosis at voles and monkeys, leprosy at rats are described. They it is long exist as «experiments in the nature», accidentally gaining scientific value. During the studying of influence on a macroorganism of corticosteroids, immunodepressants at rats the hematogenous staphylococcal infection with the ascending pyelonephritis is constantly observed. Under the influence of antibiotics at Guinea pigs, hamsters enterita develop. At the rats infected with tumor cells tetanus easily is reproduced. Laboratory animals against the background of a burn disease spontaneously have an infectious process caused by staphylococcus, a pyocyanic stick, escherichias and Proteus.
Sometimes introduction of microorganisms an animal is not followed by I. Okazalos's development, such modeling has scientific value too; such «negative» models can be used for studying of mechanisms of elimination of the activator, areactivity to effect of toxins and other phenomena of natural (specific) immunity. It is established that not only specific resistance, but also ability to formation of active immunity is genetically determined. The relevant data were for the first time obtained in overseeing mono - and dizygotic twins; however this situation is significantly specified during the modeling of processes of an infection and immunity on animals of pure lines, especially on mice.
Reproduction of an experimental infection is important and for assessment to lay down. - professional, drugs. In experiences of so-called active (vaccine) and passive (immune serums) protection of laboratory animals harmlessness, antigenicity and an immunogenicity of drugs is studied. At the same time assessment of harmlessness is conducted not only on effect of death or survival of animals; also the complex of disturbances of their general state (body weight, temperature reaction, a wedge, displays of intoxication or infection) and changes on site administrations of drugs (hypostasis, a hyperemia, infiltrates, necroses), and also development of the phenomena of a sensitization and autoimmune processes is registered.
At approbation of preventive drugs, especially live vaccines, carry surely out studying patomorfol. changes at the animals imparted by them. In particular, define distribution of vaccinal strains and their antigens in various bodies, and also existence specific, typical for this infectious process at the person and nonspecific disturbances in morphology of bodies and fabrics.
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A. A. Sumarokov, 3. M. Andreyeva, H. M. Nikityuk, L. I. Pavlova, R. G. Shepilova.