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BACTERIA - pathogens of diseases in humans and animals Completed by: Student of the 11th group Department: General Medicine Natalya Mikhalchenko

Pneumonia has long become one of the most common diseases among children and adults. And this is not strange, because every third person suffers from pneumonia at least once in his life. It is impossible to find a “mild form” of pneumonia, because each of its forms has its own characteristics and potential danger to human life. Some forms of inflammation are considered more dangerous in the severity of their complications. A big problem is establishing the exact cause of pneumonia, because each form requires individual treatment.

Streptococcal pneumonia is an inflammation of the lung tissue that is caused by bacteria of the genus streptococcus pneumoniae. Pneumonia caused by streptococcus pneumonia is relatively rare - in approximately 1/5 of all cases of pneumonia in children and adults. Due to the specificity of the pathogen, the disease begins acutely. Rapidly developing symptoms almost always force the patient to consult a doctor, which facilitates timely initiation of treatment. In very rare cases, streptococcal inflammation is asymptomatic, which is typical for latent pneumonia. Most often, the disease occurs against the background of measles, influenza, chicken pox, or whooping cough. Streptococcus often causes pneumonia in children. This is due to the anatomical and physiological structure of the lungs and airways.

The disease begins acutely with a rise in body temperature, severe chills, myalgia, arthralgia, shortness of breath, cough, hemoptysis, loss of performance, severe fatigue, and pain in the side. Intoxication of the body is rapidly developing. In severe cases, the patient develops symptoms of respiratory or cardiovascular failure, which can lead to serious consequences. In this case, acrocyanosis, memory loss, tachycardia, arrhythmias, and asthma attacks are noted. With the development of exudative pleurisy, the patient complains of pain in the side. In this case, there is a displacement of the mediastinal organs to the side. Exudative pleurisy develops in children very often - in 1/3 of cases. In some cases, the pathological process can lead to chronic abscesses in the lungs. Also, streptococcal pneumonia can lead to the development of purulent pericarditis, glomerulonephritis, and sepsis.

TREATMENT OF STREPTOCOCCAL PULMONARY With timely and correct treatment, recovery occurs in 6-10 days. It is very important that the patient remains in bed during treatment. After identifying the pathogen, the patient is prescribed specific antibiotics. To correct intoxication, a loading dose of diuretins is used and patients are given large amounts of water and tea. To correct dysbiosis, the patient is prescribed eubiotics. The use of multivitamin complexes also has a positive effect for treatment. In case of development of exudative pleurisy, drainage of the pleural cavity is indicated, followed by its washing with antiseptics or antibiotics. With adequate and timely treatment in children and adults, the chance of complications is significantly reduced, which will most likely save a person’s life.

The causative agent of anthrax is Bacilla anthracis (Cohn, 1872) - a typical representative of pathogenic bacilli. Belongs to the family Bacillaceae and the genus Bacilus. This microbe is often called the anthrax bacillus. Anthrax (Anthrax) is a zooanthroponosis. Animals of many species, especially herbivores, and humans are susceptible to it. The infectious process occurs predominantly acutely with symptoms of septicemia or with the formation of carbuncles of varying sizes. The disease is recorded in sporadic cases, enzootics and even epizootics are possible. The name of the disease “anthrax” was proposed in 1789 by S. Andrievsky, who studied it in the Urals and Siberia. Microscopically, the anthrax bacillus was discovered by Pollender in 1849. French researchers Daven and Reis (1850), and in Russia, Professor of the Dorpat Veterinary School Browell (1857) also noted the presence of thread-like immobile and non-branching bodies in the blood of sheep sick and dead from anthrax. Brauel was one of the first to identify bacilli in the blood of a person who died from anthrax, and experimentally reproduced a typical disease in animals when they were infected with blood containing microscopically visible bacilli. However, the significance of these rods remained unclear until 1863, when Daven finally established the role of these formations as pathogenic agents of anthrax. Pure cultures of the anthrax bacillus were isolated in 1876, first by R. Koch and then by L. Pasteur; Independently of one another, with the help of these cultures they reproduced the disease in animals.

The anthrax bacillus is a rather large (1 - Anthrax bacillus at 1.3 * 3.0 - 10.0 microns) rod, immobile, forms a capsule and spore under unfavorable conditions of existence. The microbe has the ability to form and occurs in three forms: in the form of a spore. In each vegetative cell, or vegetative sporangial cells of various sizes, only one is formed (capsular and acapsular), in the form of an endospore, often located spores, enclosed in a well-defined centrally, less often subterminally. exosporium, and in the form of isolated spores. The spores of the anthrax bacillus are oval, sometimes In colored preparations from blood and round, strongly refracting light from the tissues of patients or those who died from the formation. The sizes of mature spores of animal anthrax bacteria range from 1.2-1.5 microns and are located singly, in pairs and in the form of length and 0.8-1.0 microns in diameter, short chains (3-4 cells); ends immature spores (prospores) several rods facing each other, smaller. At temperatures below 12 and above, straight, sharply chopped, free - 42 0 C, as well as in a living organism or slightly rounded. Sometimes the chains in an unopened corpse, in blood and serum, have the shape of a bamboo cane; In this animal, spores are not formed. In this case, the microbial cells seem to be chopped off, partly pressed into the middle and symmetrically thickened at the joints. Such morphological forms are found in bacteria that have formed a capsule.

The anthrax bacillus is highly invasive and easily penetrates through scratches in the skin or mucous membranes. Infection of animals occurs mainly through nutrition. Through the damaged mucous membrane of the digestive tract, the microbe penetrates into the lymphatic system, and then into the blood, where it is phagocytosed and spread throughout the body, fixing itself in the elements of the lymphoid-macrophage system, after which it again migrates into the blood, causing septicemia. When multiplying in the body, the anthrax bacillus synthesizes a capsular polypeptide and releases an exotoxin. The capsular substance inhibits opsonization, while the exotoxin destroys phagocytes, affects the central nervous system, causes edema, hyperglycemia and increased alkaline phosphatase activity. In the terminal phase of the process, the oxygen content in the blood decreases to a level incompatible with life. Metabolism is sharply disrupted, secondary shock develops and the death of animals occurs. The causative agent of anthrax can be excreted from the body in bronchial mucus, saliva, milk, urine and feces.

All species of mammals are susceptible to anthrax. Under natural conditions, sheep, cattle and horses are more likely to get sick, and imula donkeys can become infected. Goats, buffalo, camels and reindeer are extremely susceptible. Pigs are less sensitive. Among wild animals, all herbivores are susceptible. There are known cases of the disease in dogs, wolves, foxes, arctic foxes, and among birds - ducks and ostriches.

V. cholerae was isolated by R. Koch in 1882, and V. eltor at the El Tor quarantine station also in Egypt. Other genera of this family contain opportunistic species (V. proteus, Vibrio Metchnikoff, V. plesiomonas, luminous vibrio), which can cause gastroenteritis.

Slightly curved gram-negative polymorphic rod. Monotrich. Does not form spores or capsules. Vibrios are chemoorganotrophs with oxidative and fermentative types of metabolism. Many carbohydrates are fermented: glucose, maltose, sucrose and others with the formation of acid. They liquefy gelatin, form indole, and reduce nitrates to nitrites. They produce enzymes such as lecithinase, lysine decarboxylase, ornithine decarboxylase, neuraminidase. The ability to reduce nitrates and form indole underlies the positive nitrosoindole test for the cholera mouth reaction. Vibrios grow well on simple media with an alkaline reaction. H = 8.5 9.0. On solid media they form small transparent round colonies, on liquid media they form a film with a slight turbidity of the medium. Vibrios are facultative anaerobes and form cytochrome oxidase. Vibrios cholerae have two antigens: O antigen, a type-specific thermolabile one, and H antigen, a flagellar species-specific thermostable one. The causative agents of cholera have 01 antigen. Vibrios belonging to serogroups 02, 03, 04 can cause enteritis and gastroenteritis. 01 antigen consists of three components A, B, C, different combinations of which form the serovars Ogawa (AB), Inaba (AS), Gikoshima (ABC). Vibrios that are not agglutinated by 01 antiserum are often isolated. They are called non-agglutinating NAG vibrios.

Plague bacillus (Yersinia pestis) is a gram-negative bacterium of the Enterobacteriaceae family. The shape of Yersinia pestis is bipolar cocobacillus. Just like other members of Enterobacteriaceae, they have enzymatic metabolism. Y. pestis produces antiphagocytic mucus. A bacterium moving in isolation becomes immobile once it enters the body of a mammal. Yersinia pestis is the infectious agent of bubonic plague and can also cause pneumonia and septicemic plague. All three forms are responsible for high mortality rates in epidemics that have occurred in human history, such as the Great Plague or the Black Death, the latter of which killed a third of the population of Europe between 1347 and 1353. However, the role of Yersinia pestis in the Black Death is controversial. Some argue that the Black Death spread too quickly to be caused by Helicobacter pylori. DNA from this bacterium, however, has been found in the teeth of people who died from the Black Death, while testing of medieval remains of people who died from other causes was not positive for Yersinia pestis. This proves that Yersinia pestis was at least a contributing factor in some (perhaps not all) European plague epidemics. It is possible that the selection effected by the plague could influence the pathogenicity of the bacterium, eliminating individuals who were most susceptible to it.

Typhoid fever, severe The causative agent of typhoid fever, Salmonella, is an acute infectious disease, typhi was discovered in 1880 by K. Ebert, characterized by deep general a, isolated in pure culture in 1884, K. intoxication, bacteremia and Haffka. Soon, the causative agents of paratyphoid A and B, S. paratyphi of the lymphatic apparatus of the small A and S. paratyphi B, were isolated and studied for specific lesions. The genus Salmonella includes the intestines. Intoxication manifests itself in a large group of bacteria, but only in severe headache, confusion (three of them S. typhi, S. paratyphi A and S. consciousness), delirium (typhoid from the Greek typhos paratyphi B causes disease in fog). Typhoid fever as an independent person with a clinical picture of a nosological unit for the first time of typhoid fever. Morphologically, they tried to isolate the Russian doctor A. G. indistinguishable short Pyatnitsky back in 1804, but finally gram-negative rods were done in 1822 by R. Bretonneau, who, with rounded ends, 1 3.5 long, differentiated this disease from µm in diameter 0.5 0.8 µm; spores and capsules of intestinal tuberculosis and do not form, they have an active assumption of the contagious nature of motility (peritrichous). Contents of typhoid fever. + C in DNA is 50 52 mol%.

The term “angina” has been known since the times of ancient medicine; most often this term refers to various painful conditions in the throat area, similar in their symptoms. However, in essence, the causes of sore throats can be completely different. In this regard, all sore throats can be divided into three categories: primary, specific and secondary (symptomatic). Primary sore throat is understood as an acute infectious disease of predominantly streptococcal etiology, with relatively short-term fever, general intoxication, inflammatory changes in the lymphoid tissues of the pharynx, most often in the palatine tonsils and the lymph nodes closest to them. Sore throat is dangerous due to the development of autoimmune processes, which without specific antistreptococcal treatment can lead to the development of acute glomerulonephritis and rheumatism, accompanied by serious damage to the kidneys and heart.

The most common causative agent of sore throat is beta hemolytic streptococcus (up to 90% of all cases). Less commonly (up to 8%), the cause of sore throat is Staphylococcus aureus, sometimes in combination with streptococcus. Very rarely, the causative agent is streptococcus pneumoniae, Haemophilus influenzae, and corynebacteria. The source of infection in sore throat is a patient with various forms of acute diseases and a carrier of pathogenic microorganisms. Patients with foci of infection in the upper respiratory tract are of greatest importance. The main route of infection for tonsillitis is through airborne droplets, which is easily carried out in large groups, in close contact with a sick person. Infection can occur by consuming foods contaminated with staphylococcus (salad, milk, minced meat, compote)

The incubation period for angina lasts 1-2 days. The disease begins acutely: in the midst of complete health, chills, headache, aching joints, general weakness, and sore throat when swallowing appear. Manifestations of the disease are most pronounced with lacunar angina: there is severe chills, body temperature can reach 40°, appetite and sleep are disturbed. The sore throat gradually intensifies, becomes constant, and reaches a maximum on the second day. Primary tonsillitis is characterized by the symptom of bilateral pain when swallowing. In the absence of pain at all or any vague sensations from the pharynx, the diagnosis of primary angina is doubtful. There is no rash with a sore throat. Mandatory for primary tonsillitis is enlargement and pain of the lymph nodes in the area of the angles of the lower jaw: when palpated, they are easily displaced. When examining the pharynx, you can see reddened (hyperemic), enlarged tonsils, with pinpoint yellowish formations (2-3 mm) with follicular and fibrinous purulent deposits of irregular shape in lacunar angina. In severe cases of tonsillitis, dark gray areas of necrosis (necrosis) may appear in the tonsils, which are then rejected, and in their place tissue defects up to 1 cm in size, often irregular in shape with an uneven bottom, form.

Single-celled microorganisms or bacteria (rods in Greek) are characterized by the presence of cytoplasm, a nucleus in which there is no nuclear envelope. They belong to prokaryotes. They, like other types of microorganisms, are widespread in watery soil and in the air, colonize the skin and colonize the mucous membranes of the human body and animals. Some of the bacteria are used in the food industry (for the purpose of preparing lactic acid products). Medicine uses them to restore the intestinal microflora through the use of drugs whose contents are filled with lyophilic bacteria. Their use in biotechnology is limited to the preparation of compounds. Bacteria are the causative agents of hepatitis scabies.

Saprophytic bacteria are more common than others. Dead organic residues are suitable for their nutrition, without which mineralization of organic elements - ammonification and nitrogen fixation - will not occur. This class of bacteria is represented by clostridia, azotobacter, mycobacteria, and blue-green algae. With the participation of saprophytes, a process associated with the circulation of carbon, oxygen, nitrogen, phosphorus, as well as sulfur and iron is carried out. Some of them are characterized by the ability to break down cellulose, keratin, oxidize and form hydrocarbons - methane, propane. It is possible to think about the use of some saprophytes for the purpose of carrying out wastewater treatment processes, and as destroyers that carry out the biodegradation of waste of various types. Saprophytes are also widely used in biotechnology. A small part of bacteria is divided into pathogenic and opportunistic bacteria. Pathogenic bacteria cause infectious diseases in humans and animals. If the body's resistance is weakened, opportunistic bacteria cause purulent-inflammatory processes.

Bacteria are most often characterized by the presence of a thin cell wall and are mainly Gram-negative types; Bacteria with thick cell walls are mostly gram-positive. There are those bacteria that do not have a cell wall at all, for example mycoplasmas. And there are archaebacteria, the difference of which is a defective cell wall, structural features of ribosomes, membranes, and also the dissimilarity of 16S- and 5S-ribosomal RNAs. Archaebacteria do not include pathogens of infectious diseases. Mainly, the division of bacteria occurs according to features associated with the structure of the cell wall and its connection with the possible variability of Gram staining of bacteria.

Coco-shaped bacteria are considered to be of the gram-positive type, as are rod-shaped bacteria. These include actinomycetes - branching, corynebacteria (club-shaped bacteria), as well as mycobacteria, presented in some cases in a branching model. Those bacteria that have lost their cell wall under the influence of antibacterial agents or due to the protective characteristics of the human or animal body are called L-forms. Next to them are mycoplasmas - bacteria that do not have a cell wall.

The main feature that distinguishes bacteria is a type of respiratory process. Molecular oxygen is what determines their division into main categories. Accordingly, bacteria can be obligate aerobes, obligate anaerobes and facultative anaerobes. Obligate aerobes spread due to the presence of oxygen, obligate anaerobes - in an environment that excludes the presence of oxygen, which is toxic to them. The development of facultative anaerobes can occur both in an oxygen environment and in the absence of it.

What bacteria are causative agents of diseases in plants, animals and humans?

Microorganisms are the most numerous inhabitants of the planet. Among them there are both beneficial for humans, plants and animals, as well as pathogenic bacteria and pathogens.

Due to the introduction of such pathogenic microbes into living organisms, infectious diseases develop.

In order for bacteria that cause diseases in plants, animals, and humans to cause infection, they must have certain properties:

pathogenicity (the ability of pathogens to invade a living organism, multiply and provoke the development of pathologies);

virulence (the ability of pathogens to overcome the resistance of a living organism); the higher the virulence, the fewer bacteria can cause damage;

toxicity (the ability of pathogens to produce biological poison);

contagiousness (the ability of pathogenic bacteria to be transmitted from a patient to a healthy body).

A significant factor in the characteristics of bacteria that cause infectious lesions is the degree of their resistance to external factors. High and low temperatures, solar radiation and humidity levels have a depressing effect on the activity of bacteria to varying degrees.

For example, the ultraviolet component of sunlight is a powerful bactericidal agent. A similar effect on pathogens of infectious diseases is exerted by various chemical disinfectants (chloramine, formalin), which can quickly lead to the complete death of pathogenic microflora.

Based on the type of toxins they produce, all bacteria belong to one of two types:

releasing exotoxins (toxic waste products of bacteria);

sources of endotoxins (toxic substances are formed during the destruction of bacterial bodies).

The most well-known bacteria that produce exotoxins are the causative agents of tetanus, botulism and diphtheria, and those producing endotoxins are pathogenic agents, the causative agents of typhoid fever, dysentery and cholera.

A characteristic feature of infectious lesions of a living organism by bacteria, pathogens, is the incubation period.

The incubation period for a disease caused by bacteria is the time interval from the moment of infection by the pathogen until the manifestation of characteristic symptoms of the lesion. The duration of the incubation (latent) period for each disease is different; the numerical value and degree of activity of the pathogenic bacteria that enter the living organism also matter.

Main types of disease classifications

There are various classifications of lesions caused by pathogenic microorganisms.

1. Infectious diseases are divided into two groups:

anthroponoses - characteristic only of humans, the source of infection is an infected person;

zoonoses – diseases characteristic of animals and humans; the infection is transmitted from an infected animal to humans; humans are not the source of infection.

2. According to the location of pathogenic microbes in the human body (classification by L.V. Gromashevsky):

intestinal;
blood infection;
respiratory tract damage;
damage to the outer covering.

3. Grouping of diseases by pathogen.

4. Classification based on epidemiological characteristics (routes of transmission of pathogens and methods of preventing an increase in the number of infected people).

Bacteriological damage to plants

Bacteria that cause diseases of plant organisms are called phytopathogenic.

Plant infection can occur in several ways:

affecting tubers;

through infected seeds;

when grafting infected cuttings and more.

In case of pathology caused by phytopathogenic microflora, various options for damage to the plant organism by the pathogen are possible:

general, causes plant death;

parts of the plant (appears on the roots or in the vascular system);

local lesions - the disease does not spread beyond a single part or organ of the plant;

parenchymal infections - cause rot, burns or spots;

formation of neoplasms (tumors).

The causative agents of plant bacterioses are mostly polyphagous bacteria found in the soil. They penetrate plants in two ways:

through the natural physiological openings of the plant (water pores, stomata);

as a result of mechanical damage to plant tissues.

When a plant is infected with pathogens such as phytopathogenic bacteria, several types of damage may occur at once, and in the same plants the same pathogenic bacteria can cause completely different symptoms, which significantly complicates the diagnosis of the disease.

Infectious lesions of animals

Animals, like plants, are susceptible to bacterial infection. Significant animal infections caused by bacteria are:

Infected animals also pose a threat to humans, since as a result of contact or through a carrier (blood-sucking animals), infection with the causative agent of the disease is possible.

Infectious animal diseases that can be transmitted to humans are called zoonoses. In this case, the source of infection is an infected animal, from which, under certain conditions, transmission of the bacteria that cause the disease to humans is possible.

Depending on the source of infection, all zoonoses are divided into:

psittacosis – the source of infection is domestic and indoor birds;

zooanthroponoses - the source of pathogens is domestic and farm animals.

Pathogens of human diseases

The human body contains more than 1000 different bacteria, and only 1% of this number is pathogenic microflora. If the microbial balance is maintained, the disease is not able to develop; in addition, the human immune system suppresses the development of any pathogenic microflora. In addition, intact skin is an insurmountable barrier to pathogens.

Pathogen bacteria that cause human diseases belong to several groups:

The mere presence of pathogenic bacteria in the human body is not a fact of disease - pathogenic microflora can exist in the human body for a long time without showing its destructive properties. And what is the trigger mechanism that causes diseases is not yet entirely clear.

Intestinal infectious diseases are among the most common - every person has suffered from infectious intestinal diseases more than once during their life. This is due to the fact that food and water are not sterile, but even to a greater extent the culprits of intestinal diseases are:

failure to comply with basic sanitary standards;

failure to comply with personal hygiene standards;

violation of food storage rules;

the presence of infection carriers (flies, mosquitoes, mice, etc.).

Bacterial pathogens that enter the body through the fecal-oral route of infection are a typical intestinal infection. Bacterial pathogens of gastrointestinal infections include staphylococcus, typhoid bacillus, Vibrio cholerae, salmonella and dysentery bacillus.

Regardless of the nature of the microbial pathogens, the characteristic signs of any intestinal diseases are:

This reaction of the human body is protective and is designed to quickly remove toxic substances that have entered the gastrointestinal tract.

Pathogens of intestinal infections, once in the intestines, lead to disruption of the digestive processes and, as a result, inflammation of the mucous membranes of the gastrointestinal tract. Which naturally leads to the most characteristic symptom of intestinal infections – diarrhea.

Although the presence of diarrhea and vomiting is most typical for intestinal pathogens, there are some diseases, for example, hepatitis A, for which these symptoms are not typical.

Bacterial infections of the intestines are life-threatening diseases - due to heavy secretions in the body, dehydration quickly occurs, which is accompanied by a massive loss of potassium (K), sodium (Na) and calcium (Ca) salts. Violation of the water-salt balance of the body can quickly lead to death.

Infectious intestinal diseases caused by pathogenic bacteria are subject to therapeutic treatment using eubiotics (beneficial bacteria) and modern enterosorbents. In this case, be sure to drink plenty of fluids and have a specific diet.

Infectious respiratory diseases

The causes of respiratory diseases, according to the results of studies, in 25% of cases are viral influenza, the remaining cases of acute respiratory infections include bacterial infections causing diphtheria, scarlet fever, whooping cough, mycoplasmosis, chlamydia, legionellosis and others.

All of them are characterized by airborne transmission of infection; the source of infection with bacterial respiratory diseases are bacteria carriers and sick people.

The causative agents of respiratory bacterial diseases are various bacteria:

diphtheria – corynebacterium diphtheria, both rod-shaped and coccal forms;

scarlet fever - streptococci;

whooping cough is a rod-shaped gram-negative bacterium;

meningococcal infection - gram-negative diplococci;

tuberculosis – gram-positive mycobacteria.

Like any bacterial disease, respiratory bacterial diseases have an incubation period, after which the diseases are acute, almost all are accompanied by various kinds of cough, rhinitis, fever, pain in the chest and fever (38-39°C).

Respiratory diseases caused by bacteria are characterized not only by damage to the respiratory tract - infection of the genitourinary organs, musculoskeletal and nervous systems, liver, skin and other organs is possible.

Respiratory diseases caused by bacterial pathogens are treated therapeutically using various antibacterial agents, in particular bacteriophages and antibiotics are used.

Mass diseases and ways of localizing infection

Infectious diseases are divided into 4 groups according to localization:

intestinal infections with a fecal-oral transmission mechanism;

respiratory diseases with airborne infection;

blood – a transmissible (through the patient’s blood) way of spreading the infection;

infections of the outer integument - infection occurs through direct contact with a patient or indirectly through objects.

In three cases out of four, infected objects and waste products are released into the environment, where water and air contribute to the rapid spread of infections. The proportion of infectious diseases spread through food is also significant.

For example, an outbreak of a mass disease of typhoid fever or dysentery is a consequence of the pathogen entering either the water supply network or open water bodies. This is possible in case of accidents in sewerage systems or during wastewater discharge.

Even in this case, mass disease can be avoided by observing basic personal hygiene measures.

Patients with infectious diseases caused by bacteria are subject to treatment in special infectious diseases departments and hospitals.

In situations of mass infection, to prevent further spread of pathogenic microflora, which is the causative agent of the disease, restrictive regime measures are carried out - quarantine and observation.

In the Middle Ages, during epidemics, infected cities and villages were simply burned along with everyone who was there to prevent the spread of disease pathogens.

What bacteria are pathogens? Bacteria and humans

The main component of a bacterial cell is water. It occupies 80% of the total mass of the microorganism. However, in disputes its content is much less - about 20%. Many bacteria tolerate a decrease in the amount of water (drying) quite well. At the same time, metabolic processes slow down and they stop reproducing. In addition, the cell contains proteins, carbohydrates, fats, as well as minerals and nucleic acids.

Bacterial cells make movements thanks to a special organ - flagella. These are thin thread-like formations, their number and location are varied. Their thickness is approximately 0.01-0.03 microns. There are several types of them. If there is only one flagellum and it is located at one pole, such bacteria are called monotorichs. Microorganisms that have a bundle of flagella at one of the poles are monopolar lophotrichs. Those bacteria that have bundles at the poles are called amphitrichous. But if the entire surface of the cell is covered with flagella, then these are peritrichous. Another way bacteria move is by sliding. It is believed that this occurs due to the fact that the cells contract in waves.

The method of reproduction in bacteria is quite simple. Its essence lies in the fact that the cell divides into two, having reached a certain size. First, it lengthens, then a transverse septum appears, and sets of cells diverge to the poles. If favorable conditions are created, bacterial division can occur every 20 minutes. But most organisms die under the influence of the environment. To survive unfavorable conditions, bacteria are able to form spores. In this state, they are able to maintain vital activity for thousands of years. Bacterial spores have been found even in ancient mummies. They are formed in several types: inside, in the middle or at the end of the cell.

Globular. These bacteria are causative agents of various diseases. These include staphylococci (have the shape of grapes), streptococci (form a long chain). The latter microorganisms are the cause of inflammatory processes and diseases such as sore throat, otitis media, and pneumonia. Staphylococcal bacteria are causative agents of diseases of the food tract and purulent processes. The most dangerous representative is Staphylococcus aureus.
Spiral. They got their name from their curled shape. These include spirilla, which are a fairly harmless organism. Spirochetes look like a thin twisted thread. These bacteria are known to be the causative agents of syphilis.
Vibrios. Representatives of this category have a slightly curved shape. They have a characteristic feature: such pathogenic bacteria are stable in an alkaline environment. They cause a disease such as cholera.
Mycoplasmas. A feature of this type is the absence of a cell membrane. Outside the host's body, they are not capable of life. The question of which disease is caused by mycoplasma bacteria has a fairly simple answer: they mainly provoke the appearance of diseases in cattle or plants.

One of the most dangerous infections is cholera. It affects the digestive organs and causes severe intoxication of the body. What bacteria are the causative agents of cholera? These microorganisms were discovered by Robert Koch. Vibrio cholerae has the shape of a slightly curved rod. A distinctive feature of these bacteria is their high mobility. Vibrio cholerae enters the small intestine and takes hold there. There they produce protein toxins, as a result of which the water-salt balance is disrupted and the body becomes severely dehydrated. Bacteria are resistant to alkaline environments, but acid is harmful to them. In addition, despite the fact that they tolerate low temperatures well, boiling kills Vibrio cholerae instantly. Infection is possible through contact with a sick person, through food or water. The incubation period is 5 days.

Pneumonia is a fairly serious disease that can be fatal. Children suffer especially hard from pneumonia. It can be caused not only by viruses. The answer to the question of which bacteria are the causative agents of the disease is known: these are pneumococci (up to 90%). Staphylococci (about 5%) and streptococci also provoke the appearance of inflammatory processes. Bacteria are located in the nasal passages and throat.

The most common symptoms of pneumonia are high fever, difficulty breathing, and general intoxication of the body. One of the most dangerous is intrauterine pneumonia. It can be caused by group B streptococci and Staphylococcus aureus. Often this disease occurs as a result of influenza. Bacterial pneumonia is treated with antibacterial drugs. In particularly severe cases, such as a young patient, hospitalization is necessary. Prevention methods include vaccination and promotion of breastfeeding for up to six months (exclusively breast milk). It is also important to monitor personal hygiene and indoor air purification.

Only recently was it established that chlamydia is a bacteria. What disease is caused by bacteria of this type? First of all, they can cause conjunctivitis of the eyes, urogenital infection, and trachoma. A special type of chlamydia causes pneumonia and acute respiratory diseases. Once in the host cells, microorganisms begin to divide. The entire cycle takes approximately 72 hours, resulting in the destruction of the affected cell. This infection is especially dangerous for women. It plays a significant role in the formation of infertility. If a fetus is infected with chlamydia, there is a high probability of its death. That is why it is important to undergo testing before planning a pregnancy, since such an infection is often asymptomatic.

Causative agents of scabies and other diseases

Quite often, amateurs wonder whether bacteria really are the causative agents of scabies. This is, of course, not true. A disease such as scabies is caused by a mite, which, when it comes into contact with the skin, begins to multiply intensively, thereby causing itching. But a complication of this disease - pyoderma, that is, purulent lesions of the skin - can be caused by bacteria of the coccus group. Special ointments are used as treatment, and clothes and linen are also disinfected.

The question of which bacteria are the causative agent of hepatitis is also relevant. Basically, hepatitis is the general name for inflammatory liver diseases. They are mainly caused by viruses. However, there is also bacterial hepatitis (with leptospirosis or syphilis). Leptospira, Treponema - these bacteria are the causative agents of hepatitis.

Another serious disease is malaria. The disease is transmitted to humans through the bites of insects (malarial mosquitoes). It is accompanied by fever, an increase in the size of the liver (possibly the spleen), and high temperature. If treatment is not started in time, death is possible. The causative agents are malaria bacteria of the genus Plasmodium. To date, 4 types of such microorganisms are known. The most dangerous is the one that can cause tropical malaria. As you can see, bacteria are pathogens that have serious complications and require medical attention.

Bacteria that are causative agents of dangerous infectious diseases

The basis of many infectious diseases is the action of pathogenic bacteria on the body. Bacteria are the causative agents of the most common infections. Famous scientists such as Alfred Koch, Leeuwenhoek, Louis Pasteur and many others devoted their activities to the study of such microorganisms.

It has been proven that it is not the microbes themselves that have a pathogenic effect on the body, but the toxins they secrete. During illness, some of these toxic substances enter the human body during the life of bacteria, while others are released after the death of the microbe. Studying the characteristics of the life activity of pathogens makes it possible to most effectively influence them with medications. Bacteria can be pathogens in diseases that are very dangerous to human life, such as anthrax or plague. Let's look at the most dangerous pathogenic bacteria and the diseases caused by them.

Mycobacterium tuberculosis

One of the most common bacteria is the causative agent of tuberculosis. The causative agent of this disease is a mycobacterium (Koch bacillus). The tuberculosis bacterium has a length of 10 nm and a diameter of 0.2 to 0.4 microns. Like all bacteria that cause infectious diseases, this microorganism has a cell wall and a cytoplasmic membrane, nuclear substance (DNA) and cytoplasm.

The causative agent of tuberculosis is a nonmotile, capsule- and spore-forming bacterium. The mycobacterium is quite resistant to the environment: for example, it can survive in water for about 5 months. The most favorable environment for the development of the tuberculosis pathogen is a damp and dark environment, since the sun's rays cause its death within 2-3 minutes. Mycobacterium tuberculosis is resistant to alcohol and acids. To study tuberculosis bacteria, the Ziehl-Neelsen staining technique is used.

The causative agent of tuberculosis can contribute to the development of a pathological process in various systems of the body, but most often it is localized in the respiratory tract. The disease caused by these microbes does not have an acute onset, which is typical for other infectious diseases. This feature is due to the absence of its own toxins in the bacterium. Clinically, this disease manifests itself:

weakness,

night sweats,

chills,

low-grade body temperature,

a prolonged cough, sometimes with streaks of blood in the sputum.

The tuberculosis bacterium enters the human body in early childhood, but the disease occurs in only one in ten cases. The body's response to a pathogen depends on the immune system. The main diagnostic methods used to identify this disease are:

To identify Mycobacterium tuberculosis, blood, sputum, and urine are examined. Only a positive laboratory and instrumental response can reliably indicate the development of the disease.

The following antibacterial drugs are used to treat tuberculosis: rifampicin, ethambutol, isoniazid, streptomycin.

Anthrax infection

One of the most dangerous infectious zoonotic diseases is anthrax. This disease is of great epidemiological significance. The causative agent of anthrax is a nonmotile gram-positive bacterium that forms spores. The causative agent of anthrax (Bacillus anthracis), due to its ability to form spores, can maintain its vital activity in the environment for decades.

Clinical manifestations of anthrax are characterized by the presence of fever, specific ulcerative defects (carbuncles) on the surface of the mucous membranes and on the skin, and damage to the intestines and lungs is also possible. Accordingly, cutaneous, intestinal and pulmonary forms of anthrax are distinguished. In rare cases, a primary septic form of anthrax is observed. The source of infection by the causative agent of this disease is cattle.

Diagnosis of anthrax is based on epidemiological history, clinical manifestations and laboratory tests. For bacteriological examination of the causative agent of anthrax, material is taken from the ulcer, sputum, feces, vomit, and blood. The response from laboratory tests is important both for making a final diagnosis and for prescribing treatment.

Treatment of anthrax is based on the administration of a specific serum that contains antibodies. This treatment method is quite difficult for patients to tolerate and is extremely dangerous. An alternative method of treating anthrax is the use of high doses of penicillin G, chloramphenicol, tetracyclines, and streptomycin.

Plague is one of the deadly diseases of important epidemiological significance. Plague is characterized by fever, severe intoxication syndrome, pneumonia, septicemia and damage to the lymph nodes. Plague is caused by a Gram-negative bacillus that does not have motor activity, Yersinia pestis.

The carriers of plague are representatives of rodents and cats. Human infection with plague most often occurs through fleas. The incubation period of plague can vary from 1 to 6 days. The clinical picture can be varied, depending on the form of manifestation of the plague: bubo, cough with copious sputum, severe diarrhea, severe pain of various locations, skin lesions and many symptoms. To diagnose plague, methods such as:

bacterioscopic examination,

biological sample,

use of diagnostic plague bacteriophage,

immune response of a pathogen to specific antibodies.

Plague is treated with a number of antibacterial drugs, such as streptomycin, tetracycline, and chloramphenicol.

Cholera is another quarantine acute disease of an infectious nature. Cholera is caused by a gram-negative motile bacterium called Vibrio cholerae. The main feature of the cholera causative agent is its high mobility, which determines the use of research methods such as crushed drop or hanging drop. Cholera is considered an infectious disease of intestinal localization. The main manifestations of cholera are severe vomiting and diarrhea, which threaten the patient’s body with significant dehydration. The symptoms of cholera are due to the ability of the causative agent of this disease to produce exotoxins.

The main diagnostic methods for detecting cholera are bacterioscopy and the test response to determine dehydration in the blood. Treatment for cholera may include doxycycline, furazolidone, trimethoprine-sulfamethoxazole, and saline solutions.

Influenza pathogen

Another life-threatening disease is an infection such as influenza. The causative agent of influenza, unlike previous bacterial pathogens, is represented by the influenza virus. But it should also be considered due to the high contagiousness and danger of the disease. A distinctive feature is the presence of many strains of the influenza virus.

Infection with the influenza virus can lead not only to the development of severe illness, but even to death. Clinical manifestations of influenza are represented by a sudden increase in body temperature, fever with chills or fever (the main difference between influenza), typical manifestations of a cold, and manifestations such as dyspeptic disorders are also possible.

Persons with reduced immunity are especially prone to developing influenza. The best way to prevent infection with the flu pathogen is vaccination, which is carried out annually. However, not the last place in the prevention of influenza is played by methods aimed at increasing the body’s immune forces.

Among the huge variety of microorganisms, you can find both friends who ensure the vital functions of our body and worst enemies. Such life forms are divided into bacteria, viruses, fungi and protozoa. Sometimes these microorganisms are combined with the word “microbes”. Bacteria are the causative agents of many diseases, some species pose a serious danger to human life. However, those organisms that live in the human body, on the contrary, help the organs cope with their functions.

Bacteria, their structure

Bacteria are the simplest single-celled organisms. They have small sizes (0.5-10 microns) and different shapes. The cell of these organisms consists of a membrane and cytoplasm. The cell membrane plays an important role in the exchange of substances with the environment. The cytoplasmic membrane fits tightly to the membrane and consists of proteins, lipids and enzymes. It is responsible for the processes of removal and entry of substances into the cell, being an osmotic barrier. The main component of the cytoplasm is protein. It is here that energy processes occur that ensure the vital activity of the cell. Bacteria do not have a formed nucleus. Instead, there is a nuclear substance that contains DNA and RNA.

Chemical composition of the cell

How microorganisms reproduce. Sporulation

Depending on their shape, bacteria are classified into the following types:

Globular. These bacteria are causative agents of various diseases. These include staphylococci (have the shape of grapes), streptococci (form a long chain). The latter microorganisms are the cause of inflammatory processes and diseases such as sore throat, otitis media, and pneumonia. Staphylococcal bacteria are causative agents of diseases of the food tract and purulent processes. The most dangerous representative is Staphylococcus aureus.

Rod-shaped. This type has the shape of a cylinder. They often form spores. Such microorganisms are called bacilli. Such bacteria are the causative agents of anthrax.

Spiral. They got their name from their curled shape. These include spirilla, which are a fairly harmless organism. Spirochetes look like a thin twisted thread. These bacteria are known to be the causative agents of syphilis.

Online questions and answers

Question: What is hepatitis?

Answer: Hepatitis is an inflammation of the liver. This condition can be self-limiting or lead to the development of fibrosis (scarring), cirrhosis, or liver cancer. The most common causes of hepatitis in the world are hepatitis viruses, but it can also be caused by other infections, toxic substances (such as alcohol and some drugs), and autoimmune diseases.

There are 5 main hepatitis viruses, called types A, B, C, D and E. These 5 types pose a huge challenge due to the burden of disease and death they cause and their potential to cause outbreaks and epidemic spread . Types B and C in particular cause chronic disease in hundreds of millions of people and are collectively the most common causes of cirrhosis and liver cancer.

Hepatitis A and E are usually caused by eating contaminated food or water. Hepatitis B, C, and D usually develop as a result of parenteral contact with infected body fluids. Common modes of transmission of these viruses include transfusion of contaminated blood or blood products, invasive medical procedures using contaminated equipment, and, for hepatitis B, transmission from mother to child during childbirth, from family member to child, and through sexual contact.

Acute infection may have limited symptoms or no symptoms, or may include symptoms such as jaundice (yellowing of the skin and eyes), dark urine, fatigue, nausea, vomiting, and abdominal pain.

Question: What are the different hepatitis viruses?

Answer: Scientists have identified 5 separate hepatitis viruses, identified by the letters A, B, C, D and E. All of them lead to the development of liver disease, but there are significant differences between them.

Hepatitis A virus (HAV) present in the feces of infected people and is most often transmitted by consuming contaminated food or water. HAV can also be spread through certain types of sexual activity. Many infections are mild, and most people recover completely and remain immune to subsequent HAV infections. However, HAV infections can be severe and life-threatening. Most people in areas of the world with poor sanitation are infected with this virus. There are safe and effective vaccines to prevent HAV.

Hepatitis B virus (HBV) transmitted through contact with infected blood, semen and other body fluids. HBV can be passed from an infected mother to her child during childbirth or from a family member to a young child. Transmission can also occur through transfusions of HBV-contaminated blood and blood products, injection from contaminated equipment during medical procedures, and injection drug use. HBV also poses a risk to health care workers who suffer needlestick injuries while caring for patients infected with HBV. There is a safe and effective vaccine to prevent HBV.

Hepatitis C virus (HCV), mainly also transmitted through contact with infected blood. This can occur through transfusions of HCV-contaminated blood and blood products, injections from contaminated equipment during medical procedures, and injection drug use. Sexual transmission of infection is also possible, but this occurs much less frequently. There is no vaccine against HCV.

Hepatitis D virus (HDV) can only infect people who are infected with HBV. Dual infection with HDV and HBV may result in more severe disease and worse outcome. Safe and effective hepatitis B vaccines provide protection against HDV infection.

Hepatitis E virus (HEV), like HAV, is transmitted in most cases by consuming contaminated food or water. HEV often leads to outbreaks of hepatitis in developing parts of the world and is increasingly recognized as a significant cause of disease in developing countries. Safe and effective vaccines have been developed to prevent HEV infection, but they are not widely available.

Bacteria, their structure

Chemical composition of the cell

Movement of bacteria

How microorganisms reproduce. Sporulation

Morphology of bacteria

Depending on their shape, bacteria are classified into the following types:

Globular. These bacteria are causative agents of various diseases. These include staphylococci (have the shape of grapes), streptococci (form a long chain). The latter microorganisms are the cause of inflammatory processes and diseases such as sore throat, otitis media, and pneumonia. Staphylococcal bacteria are causative agents of diseases of the food tract and purulent processes. The most dangerous representative is Staphylococcus aureus.
Rod-shaped. This type has the shape of a cylinder. They often form spores. Such microorganisms are called bacilli. Such bacteria are the causative agents of anthrax.
Spiral. They got their name from their curled shape. These include spirilla, which are a fairly harmless organism. Spirochetes look like a thin twisted thread. These bacteria are known to be the causative agents of syphilis.
Vibrios. Representatives of this category have a slightly curved shape. They have a characteristic feature: such pathogenic bacteria are stable in an alkaline environment. They cause a disease such as cholera.
Mycoplasmas. A feature of this type is the absence of a cell membrane. Outside the host's body, they are not capable of life. The question of which disease is caused by mycoplasma bacteria has a fairly simple answer: they mainly provoke the appearance of diseases in cattle or plants.

Cholera

Pneumonia

Chlamydia

Only recently was it established that chlamydia is a bacteria. of this type? First of all, they can cause conjunctivitis of the eyes, urogenital infection, and trachoma. A special type of chlamydia causes pneumonia and acute respiratory diseases. Once in the host cells, microorganisms begin to divide. The entire cycle takes approximately 72 hours, resulting in the destruction of the affected cell. This infection is especially dangerous for women. It plays a significant role in the formation of infertility. If a fetus is infected with chlamydia, there is a high probability of its death. That is why it is important to undergo testing before planning a pregnancy, since such an infection is often asymptomatic.

Causative agents of scabies and other diseases

Quite often, amateurs wonder whether bacteria really are the causative agents of scabies. This is, of course, not true. A disease such as scabies is caused by a mite, which, when it comes into contact with the skin, begins to multiply intensively, thereby causing itching. But a complication of this disease - pyoderma, that is, purulent lesions of the skin - can be caused by bacteria of the cocci group. Special ointments are used as treatment, and clothes and linen are also disinfected.

Infectious diseases

Among the many diseases to which a person is susceptible, there is a special group of diseases that are considered to be contagious, or infectious.

Infectious diseases are diseases caused by a living pathogen that have the ability to be transmitted from a sick person to a healthy person, causing epidemics. Such pathogens, as a rule, are microorganisms - organisms that cannot be seen with the naked eye, but only with the help of more or less powerful microscopes.

But not all microorganisms pose a threat to human health. Some microbes can live inside the human body without causing disease and even help vital processes, such as digestion. According to this, all microbes on the globe are divided into three large groups: pathogenic microorganisms, that is, those that cause diseases can be:

Bacteria (cholera, sepsis, tuberculosis);

Viruses (flu, hepatitis, HIV);

Fungi (skin mycoses);

Protozoa (dysentery, malaria)

Bacteria

Bacteria are single-celled prenuclear organisms. There are more than three thousand species of them on Earth. They have microscopic sizes (from 0.2 to 1 microns). The morphology of bacteria is quite diverse, according to which they are classified in a certain way according to their shape and ability to form groups. So, the following forms of bacteria are isolated.

1. Monocoques. They do not form groups. They have a spherical cell shape. Among them, truly pathogenic forms are rarely found. The most common representatives of monococci are orange micrococcus (Micrococcus aurentiacum) and white micrococcus (Micrococcus album), which, when multiplied, form orange and white spots on food.

2. Diplococci. There are several varieties. More often there is a combination of two spherical bacterial cells covered with a mucous membrane. The nitrogen-fixing Azotobacter croococcum, the causative agent of pneumonia (Dyplococcus pneumonius), has this form. There are also combinations of two cells that look like coffee beans. These include the causative agents of gonorrhea (Neiseria honored) and meningitis (Neiseria miningitidis).

3. Streptococci. The cells are spherical in shape and form long chains. Among them there are both non-pathogenic, for example those that cause sour milk (Streptococcus lactis), and pathogenic, which cause tonsillitis, scarlet fever, and rheumatic carditis. Their characteristic feature is that in the process of life they secrete c-reactive protein, which has hemolytic properties, i.e. those that destroy hemoglobin (Streptococcus piogenes).

4. Sarcins. Several spherical bacterial cells form small groups. A characteristic feature of this type of bacteria is the formation of spores and extremely rapid reproduction. Among the representatives are Sarcina flava, which forms yellow spots on consumer products, and Sarcina urea, which decomposes urine.

5. Staphylococci. There are also pathogenic and non-pathogenic forms. For example, Staphylococcus aureus forms golden colonies in a nutrient medium and does not pose any direct threat to human health. At the same time, there are a number of extremely dangerous staphylococci that cause severe inflammation: scarlet fever, sepsis. A colony of staphylococci is always a large collection of spherical cells. A characteristic feature of this group is its strong mutagenicity - the ability to form new forms.

6. Cocobacteria. A group of bacteria is extremely common in the environment. The cells are very small rods that are sometimes difficult to distinguish from micrococci. Thus, Pseudomonas lives in water and soil, which plays an important role as decomposers. The gastrointestinal tract of humans and animals is inhabited by conditionally pathogenic Escherichia coli (Esherichia Coli), which, on the one hand, helps digestion, but, on the other, some of its forms can cause cholecystitis and pancreatitis. Among the causative agents of diseases are Salmonela tiphi, which causes typhus, Proteus vulgaris, an anaerobe, which causes painful cavities (for example, the maxillary sinus).

7. Bacilli. Evolutionarily more advanced forms of bacteria are cylindrical in shape and form spores. In addition, they can always use nutrients from the environment. The bacillary form is Bacilus subtilis, a Bacillus subtilis that quickly multiplies in warm tea, and Bacilus turingiensis, a bacterium that is of great importance for the development of environmentally friendly insecticides. It secretes a protein substance that causes paralysis of the intestinal apparatus of insects.

9. Streptobacilli. Just like streptococci, they form long chains of their cells. Pathogenic streptobacilli are found. Thus, Streptobacilus anthracis is the causative agent of anthrax.

10. Clostridia. They have a spindle-shaped shape and are characterized by anaerobic respiration. That is why most clostridia are pathogenic microorganisms. Clostridium tetani - the causative agent of tetanus, Clostridium botulinum - causes severe digestive disorders - botulism, Clostridium septicum - the causative agent of gas gangrene. Clostridium perfringens is an indicator of fecal soil contamination. Living in the body, it enriches it with enzymes, but in case of diabetes it can cause gangrene.

11. Vibrios. They belong to forms that are sometimes called sinuous. They are sticks curved less than a quarter of a circle and slightly tremble. A typical representative of vibrios is the cholera causative agent Vibrio cholera, which sometimes forms blue colonies. Its peculiarity is that it is the only one that tolerates an alkaline environment (pH greater than 7).

14. Mycoplasmas. Bacteria are interesting because they do not have a cell membrane. ) X can be considered as a transitional form between viruses and cellular life forms. A characteristic feature is that they are completely incapable of existing outside the host cell. Mycoplasmas are mainly represented by pathogens of plants and cattle.

In addition to classifying bacteria by cell shape, their color is a very important systematic feature. All methods of classifying bacteria by color are based on their different internal chemical composition. The most general method of classification is Gram staining. This method allows you to divide the entire huge number of bacterial organisms into two groups: gram-positive (become purple after staining) and gram-negative (become red after staining).

The practical significance of this taxonomy lies in the unequal sensitivity of gram-positive and gram-negative bacteria to antibiotics. Thus, gram-positive bacteria are more sensitive to penicillin antibiotics, and gram-negative bacteria are more sensitive to gentomycin and streptomycin antibiotics. This determines the methods of treating infectious diseases.

There is an interesting feature of the distribution of bacteria of different forms in the human body. Based on the percentage ratio between the types of microorganisms, one can determine the predisposition to a particular disease, prevent complications, and begin treatment on time. A sample for microflora is taken from the oral cavity, and its analysis can be easily done even at home with a microscope.

So, if streptococci and staphylococci dominate, this indicates respiratory tract diseases. If rod-shaped forms predominate (bacilli, streptobacilli, etc.), gastric tract diseases are possible. The appearance of diplococci is a sign of disease of the genital organs, candida (branched chains of spherical bacteria) is an indicator of dysbacteriosis, possibly thrush, and stomatitis develops. Spirochetes are companions of the inflammatory process in the oral cavity. If all the bacteria are in approximately the same quantity, there is no reason to worry.

Viruses

The second group of common human pathogens are viruses. A virus is an autonomous genetic unit capable of reproduction (reduplication) only in the host cell. Viruses can be considered as substances outside the cell. But once they enter the host’s body, they begin to behave like living beings.

The structure of the virus is quite simple. It consists of a piece of nucleic acid (DNA or RNA) and protein molecules that perform the function of a shell (Fig. 49). The protein shell is enzymatically active; it ensures the attachment of the virus to the host cell. Viruses are specific; they infect not only a specific type of animal, plant or human, but also certain cells of the host; for example, the polio virus infects only nerve cells and does not harm others.

Depending on the type of nucleic acid, DNA genomic and RNA genomic viruses are distinguished. DNA genomic pathogens include hepatitis B, chickenpox, and herpes zoster. RNA genomic viruses cause influenza A, B, C, measles and other diseases. A special group of viruses are the so-called retroviruses, of which the well-known HIV, the human immunodeficiency virus, is a representative. HIV attacks the cells responsible for immunity. If infected, the severe disease AIDS occurs.

The mechanism of action of viruses is that, upon entering the body, they adsorbently penetrate the host cell. Here there is a transition from an inert (crystalline) state to an active one. Next, the virus sheds its shell, releasing a piece of nucleic acid that is integrated into the genetic apparatus of the cell. Synthesis of virus components (nucleic acids, proteins) occurs. Newly formed particles rupture the cell and come out, damaging nearby cells.

The life activity of some viruses is quite specific. They can enter the human body and integrate their nucleic acid into the DNA or RNA of the host cell. But, remaining in the cage, they are in a kind of symbiosis (the phenomenon of virogeny) and do not show themselves in any way. Thus, life activity is characteristic of retroviruses.

It is known that the main cause of cancer is the action of just such viruses. A newly formed gene, which has not shown itself for a long time, begins to actively function during nervous stress, exposure to radiation, or carcinogenic substances and causes the cell to synthesize mitotic division stimulants. The resulting appearance of excess proteins leads to the formation of cancerous tumors.

Among other features of the life activity of many forms of viruses (for example, the causative agent of influenza), it should be noted the so-called antigenic drift - mutations that occur in the pathogen every 2-3 years. The content of this process is the replacement of some part of the gene. The gene is completely replaced after 8-11 years. The significance of this process lies in its counteraction by specific immunity. Interestingly, one virus, having entered the human body, protects it from the penetration of other viruses. This phenomenon is known as viral interference.

A special group of microorganisms are phages - bacterial viruses. They are more complexly constructed; under an electron microscope it can be seen that they have the shape of a comma or a club with dimensions of 5-6 nm. They consist of a head, a rod, inside of which there are special contractile proteins, and several processes.

The phage infects both pathogenic and non-pathogenic bacteria, so it was thought that it could be used to treat infectious diseases. But it turned out that inside the human body the phage loses its activity. Therefore, it can only be used to diagnose bacterial infections.

Mushrooms

The body of the fungus (mycelium) can consist of one, highly branched cell, or many. The main waste product of fungi is urea. Mushrooms reproduce extremely intensively, as a rule, by peculiar spores or budding.

Protozoa and worms

Another group of pathogens of infectious diseases are protozoa and worms.

Protozoa that cause diseases include dysenteric amoeba, coccidia, sporozoans, etc. The body of the simplest animals consists of only one cell, which performs all the functions of the whole organism. Thus, the dysentery amoeba resembles a piece of protoplasm, constantly changes its shape, and can actively move. Once in the human body, it causes a serious disease of the digestive system - dysentery.

The cause of the disease is always the penetration of a pathogen into the human body due to non-compliance with hygiene rules, violation of food preparation technology, contact with patients, etc.

Infectious diseases are caused by certain microorganisms - pathogens, are transmitted from an infected organism to a healthy one and can cause an epidemic or pandemic. Among the causative agents of infectious diseases are:

Microbes (bacteria);

Rickettsia;

Spirochetes;

Protozoa.

Bacteria– these are single-celled microorganisms that have the shape of rods (pathogens of typhoid fever, paratyphoid fevers A and B), balls (staphylococci, streptococci), winding threads (spirilla) or curved rods (vibrio cholerae). The rod-shaped form is represented by the largest and most diverse group of bacteria.

Viruses- These are the smallest microorganisms, the sizes of which are measured in millimicrons. These include pathogens of influenza, foot-and-mouth disease, polio, smallpox, encephalitis, measles and other diseases.

Rickettsia– causative agents of typhus, Q fever, etc. – occupy an intermediate position between bacteria and viruses. Rickettsiae are in the form of rods, or cocci. They are much smaller than many bacteria. Unlike bacteria, they do not grow on artificial nutrient media. Diseases caused by various types of pathogens of this group are called rickettsioses.

Spirochetes(the causative agents of relapsing fever and syphilis) have the form of thin, corkscrew-shaped, actively bending bacteria.

Fungi, or microscopic fungi, unlike bacteria, have a more complex structure. Most of them are multicellular organisms. Microscopic fungal cells are elongated, thread-like. The sizes range from 0.5 to 10–50 microns or more.

Most fungi are saprophytes, only a few of them cause diseases in humans and animals. Most often they cause various lesions of the skin, hair, and nails, but there are types that also affect internal organs. Diseases caused by microscopic fungi are called mycoses.

Depending on their structure and characteristics, mushrooms are divided into several groups.

1. Pathogenic fungi include:

A yeast-like fungus that causes a serious disease – blastomycosis;

Radiant fungus that causes actinomycosis;

Pathogens of deep mycoses (histoplasmosis, coccidoidosis).

2. From the group of so-called “imperfect fungi,” the causative agents of numerous dermatomycosis are widespread.

3. Of the non-pathogenic fungi, the most common are molds and yeasts.

Thus, the cause of an infectious disease is the penetration of a pathogenic microorganism into a susceptible organism in sufficient quantities and in a way specific to the pathogen. Most infectious diseases have an incubation period - the period of time between infection and the appearance of the first symptoms.