Microorganisms are ubiquitous in the environment. They are found in soil, water, air, human and animal bodies. Microorganisms are involved in the processes of transformation of substances, their assimilation by plants and animals.
Microorganisms have the ability to adapt (adapt) to the most different conditions environment. They are found in various combinations (associations) and quantities. Each object has its own characteristic microflora. Our knowledge of the characteristics of the spread of microorganisms helps to prevent infectious diseases and even eliminate some of them.
Soil microflora
In the soil, microorganisms find the most favorable conditions for their development. Organic matter, mineral compounds, sufficient soil moisture create conditions for the accumulation of a huge number of microorganisms in it.
The richest in microorganisms is cultivated, cultivated soil (up to 5 billion per 1 g of soil), the least is desert soil, poor in moisture and organic matter (200 million per 1 g).
The number of microorganisms in the soil is also not the same in different climatic conditions: in the southern regions it is much higher. Their distribution is uneven in different layers of the soil. So, in the surface layer of the soil, due to the destructive effect of sunlight and drying, there are relatively few microorganisms, at a depth of 10-20 cm their number reaches a maximum and then, as they deepen, their number rapidly falls.
Soil microflora is very diverse; it consists of nitrifying, nitrogen-fixing, denitrifying, cellulose-decomposing bacteria; gray and iron bacteria, fungi, algae, protozoa. Most microorganisms living in the soil take part in the cycle of substances in nature: the decomposition of organic substances to inorganic ones, the assimilation of mineral elements and the fixation of atmospheric nitrogen by plants. Microorganisms change the structure and chemical composition soil.
Soil can serve as a pathway for the transmission of infectious agents. Pathogenic bacteria enter the soil with excretions of humans and animals, corpses and waste. Most of them, due to a lack of nutrients, the influence of sunlight and the action of antagonist microbes, quickly die. However, some microorganisms persist for a time sufficient for the spread of infection (from several hours to several months). There are also microorganisms that persist for a long time (many years) in the soil, through which the infection of animals and humans occurs. These include spore-forming bacteria: pathogens of anthrax, tetanus, gas gangrene. And, finally, for some microorganisms, the soil is a permanent habitat: pathogens of botulism, actinomycetes, etc.
Water microflora
The water of open reservoirs is a natural habitat for many microorganisms. They enter the water from the soil, with excretions of humans and animals, waste, sewage.
The usual microflora of the soil is saprophytes. Pseudomonas, micrococci, vibrios live in water. In addition, pathogens of infectious diseases can get into the water, persist and even multiply. For example, Escherichia coli and typhoid pathogens survive in water for a long time, while cholera pathogens multiply.
The intensity of water contamination by microorganisms and the composition of microflora depend on the degree of pollution of the reservoir, especially organic compounds. Close to populated areas where water bodies are polluted with sewage, household and industrial waters, the number of microorganisms in the water is especially high, and the microflora is more diverse.
Self-purification processes are constantly taking place in water - microorganisms die from the action of sunlight and chemical substances, precipitation, exposure to antibiotic substances produced by other microorganisms, algae, fungi.
The water of the seas and oceans is also rich in microorganisms, but there are much fewer of them than in freshwater open reservoirs. There are especially many microorganisms in the layer of bottom silt, on which they form a thin film. The cleanest are soil waters that come to the surface through artesian wells and springs.
Water plays a big role in the transmission of infectious diseases. The causative agents of intestinal infections, poliomyelitis, tularemia, leptospirosis often cause "water" epidemics, and for cholera, water is the main route of infection transmission.
Determining the purity of water and preventing its pollution is one of the mandatory measures in the fight against infectious diseases.
Air microflora
The air does not contain nutrient substrates necessary for the development of microorganisms. In addition, solar radiation, temperature changes and other factors have an adverse effect on microorganisms. Despite this, a significant number of microorganisms are constantly in the air, which enter the air with dust from the soil surface. Most often in the air there are spores of fungi and bacteria, pigment saprophytic bacteria, mold and yeast fungi, and various cocci.
The number of microorganisms in the air varies widely.
The most polluted air in large industrial cities. IN countryside the air is much cleaner, and the least amount of microorganisms is found in the air above the forest, mountains, and seas.
There are fewer microorganisms in the upper layers of the atmosphere than in the lower ones; less in winter than in summer; more indoors than outdoors. Especially a lot of bacteria in poorly ventilated areas in the absence of wet cleaning.
Pathogenic microorganisms enter the air along with droplets of saliva and sputum, coughing, sneezing, talking sick people, as well as dust from contaminated objects and infected soil.
Microorganisms are in the air in the form of an aerosol (droplets of liquid or in the smallest solid particles suspended in the air).
Inhaling air contaminated with pathogenic microorganisms can make a person sick. This way of transmission of infection is called airborne (air-dust).
Low-resistant pathogenic microorganisms are usually transmitted only at a distance close to the patient (the causative agent of measles, influenza, whooping cough); dust particles carry cocci, spores and more resistant microorganisms. The latter include pathogens of anthrax, tuberculosis, etc. Epidemics of diseases spread through the air usually occur in winter when people gather in enclosed spaces that are insufficiently ventilated and in the absence of daily wet cleaning.
To prevent these diseases, gauze masks are used, which are used by medical personnel, patients, employees of children's institutions.
Microflora of the human body
Normal human microflora has developed as a result of the interaction of micro- and macroorganism in the process of evolution. The totality of microbial species characteristic of individual organs and cavities of the body - biocenosis - necessary condition normal functioning of the body. Violation of the biocenosis, the appearance of microorganisms unusual for it, especially pathogens, causes the development of the disease.
The human fetus is sterile during pregnancy. Already during childbirth, microorganisms enter the child's body from the birth canal of the mother. They also come from the mother's skin, the hands of staff, surrounding objects and the air.
During a person's life, the nature of the microflora changes, but in general it is constant and characteristic of individual organs. Internal organs human are usually sterile (blood, brain, liver, etc.). Organs and tissues that communicate with the environment contain microorganisms.
Skin microflora pretty constant. It is represented by staphylococci, streptococci, diphtheroids, spore-forming bacteria, yeast-like fungi. The nutrient substrate for them is the secretions of the sebaceous and sweat glands, dead cells and decay products. Microorganisms that have fallen on clean healthy skin usually die from the effects of secretions from various glands and bacteria that constantly live on the skin.
Pollution of the skin promotes the development of pathogenic microorganisms, so it is very important to keep the skin clean at all times.
The microflora of the oral cavity plentiful and varied. Constant temperature, humidity, availability of nutrients, alkaline reaction of saliva create favorable conditions for the development of microorganisms. Various types of cocci, lactic acid bacteria, diphtheroids, spirochetes predominate; spindle-shaped sticks, actinomycetes and yeast-like fungi are found.
Oral microorganisms play an important role in the development of dental caries, stomatitis, inflammation of soft tissues. In the first stage of the inflammatory process, streptococci, bacteroids, and actinomycetes predominate. As caries develops, putrefactive bacteria join them: Proteus, Clostridia, etc. Oral hygiene is of great importance in preventing these diseases.
Microflora of the gastrointestinal tract. Usually, the microflora of the stomach is extremely poor due to the destructive effect of acidic gastric juice. In the small intestine, despite the alkaline reaction, there are also few microorganisms due to the unfavorable action of enzymes. In the large intestine, conditions for the reproduction of microorganisms are more favorable. Throughout a person's life, the microflora of the large intestine changes: lactic acid bacteria predominate in infants, in adults bacteroids, bifidobacteria, E. coli, fecal streptococcus, etc. are usually found. About a third of fecal masses are various microorganisms.
The microflora of the respiratory tract. Man breathes in air great amount microorganisms. However, most of them linger in the nasal cavity or are brought out with the help of the ciliated epithelium of the upper respiratory tract. In the nasopharynx and pharynx, staphylococci, streptococci, diphtheroids, etc. are usually found. When the body is weakened (cooling, exhaustion, injuries), microorganisms - permanent inhabitants of the upper respiratory tract - can cause various diseases, affecting the lower respiratory tract (bronchitis, pneumonia ).
Microflora of the mucous membrane of the eyes very poor due to the action of lysozyme contained in tears. Nevertheless, staphylococci and diphtheroids are found on the conjunctiva.
Microflora of the vagina changes throughout a woman's life. In girls, coccal flora predominates, in adult women - Dederlein's stick.
Normal human microflora is a necessary condition for maintaining his health. Violation of microbial biocenoses in various organs and systems of the body leads to the development of pathological processes, a decrease in the body's defenses, and the development of dysbacteriosis.
test questions
1. What characterizes the microflora of soil, water, air?
2. What is the role of the normal microflora of the human body?
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The microflora of the air depends on the microflora of the water and soil, above which the layers of air are located. Microbes can multiply in soil and water, but they do not multiply in the air, but only persist for some time. Raised into the air with dust, they either settle with drops back to the surface of the earth, or die in the air from a lack of nutrition and from the action of ultraviolet rays. However, some of them are more resistant, for example, tubercle bacillus, spores of clostridia, fungi, etc., can remain in the air for a long time.
Nai large quantity microbes found in the air of industrial cities. The cleanest air is over forests, mountains, snowy expanses. The upper layers of the air contain fewer germs. Above Moscow at an altitude of 500 m, one meter of air contains 2-3 bacteria, at an altitude of 1000 m - 2 times less. The indoor air is very rich in microbes, especially in medical and preventive, preschool institutions, schools, etc. Pathogenic microbes are often found in the air along with harmless saprophytes.
When coughing, sneezing, the smallest droplets-aerosols are thrown into the air, containing pathogens such as influenza, measles, whooping cough, tuberculosis and a number of others, transmitted by airborne droplets from a sick person to a healthy person, causing disease.
Sanitary and bacteriological examination of air
The accumulation and circulation of pathogens in the air of medical institutions is one of the causes of hospital purulent-septic infections that cause enormous economic damage, increasing the cost of treatment by 2 times.
As a result, much attention has recently been paid to the sanitary-bacteriological study of air in hospitals, operating rooms, maternity hospitals, children's institutions, etc. Studies are carried out both in a planned manner and according to epidemiological indications. Bacteriological examination of the air environment provides for:
Determination of the total content of microbes in 1 m3 of air;
Determination of the content of Staphylococcus aureus in 1 m3 of air.
Air sampling for bacterial research is carried out in the following rooms:
* operating blocks;
* dressings;
« postoperative wards; « delivery rooms;
* Wards for newborns;
* wards for premature babies;
* postpartum wards;
* Intensive care units and wards and other rooms requiring aseptic conditions.
Air sampling methods
There are two main ways to take air samples for research:
1. sedimentation - based on mechanical sedimentation of microorganisms;
2. aspiration - based on the active suction of air (this method makes it possible to determine not only the qualitative, but also the quantitative content of bacteria).
Air samples are taken by aspiration using the Krotov apparatus, which consists of three main parts: base, body and cover. The lid has a disc made of transparent organic glass with a wedge-shaped slot for air intake. To determine the amount of air that has passed through the device, a rotameter is placed on the outer wall of the housing. In the upper part of the housing there is a rotating disk on which a Petri dish is placed. Air is sucked into the device centrifugal fan mounted on the axis of the electric motor. The jet of air entering the device hits the surface of the nutrient medium in the cup, leaving microorganisms on it, and, flowing around the electric motor, exits through the rotameter.
The air pulling speed is 25 liters per minute. The amount of air passed should be 100 liters to determine the total bacteria content and 250 liters to determine the presence of Staphylococcus aureus.
When taking samples in different rooms, it is necessary to treat the surface of the apparatus, the table, and the inner walls with a disinfectant solution of 70 ° alcohol.
Determination of microbial number, pathogenic microorganisms
To determine the total bacteria content in 1 m3 of air, sampling is carried out on 2% nutrient agar. The inoculations are incubated at 37°C for 24 hours, then left for 24 hours at room temperature, the number of grown colonies is counted and recalculated per 1 m3 of air. If colonies of mold fungi have grown on nutrient agar plates, they are counted and recalculated for 1 m3 of air. In the protocol, the number of mold fungi is indicated separately.
Payment. For example, 125 liters of air passed through in 10 minutes, 100 colonies grew on the surface.
100x1000 l The number of microbes in 1 m3 of air = - T -- = 800 l, i.e.
The number of grown colonies -1000 l the amount of air passed
To determine the presence of Staphylococcus aureus, sampling is carried out on yolk-salt agar (YSA). The cups are placed in a thermostat at a temperature of 37°C for 24 hours and incubated for another 24 hours at room temperature, it is possible for 48 hours at a temperature of 37°C. Colonies suspicious for staphylococcus are subject to mandatory microscopy and further identification.
From the yolk-salt agar, the colonies of staphylococci are removed first of all, which form an iridescent corolla around the colony (positive lecitovitellase reaction). Further study is also subjected to pigmented colonies and with a negative lecitovitellase reaction of at least two colonies of various types. Suspicious colonies are subcultured on blood or milk agar plates. Further study of them is carried out according to the scheme.
Bacteriological examination for staphylococcus aureus
Sowing on elective media (yolk-salt, milk-salt or milk-yolk-salt agar). The seeded media are kept in a thermostat at 37°C for 2 days, or one day in a thermostat and an additional 24 hours in the light at room temperature.
2-3rd day.
Viewing cups, fixing in the journal the nature and massiveness of growth. On the above media, Staphylococcus grows in the form of round shiny, oily, convex pigmented colonies. On media containing yolk, Staphylococcus aureus, isolated from humans, in 60-70% of cases forms an iridescent corolla around the colony (positive lecitovitellase reaction).
Agar slant for further examination of at least 2 colonies suspected of staphylococcus aureus. For the study, first of all, colonies that give a positive lecitovitellase reaction are weaved.
Tubes with seeding are placed in a thermostat at 37°C for 18-20 hours.
After a daily incubation, the isolated strains are checked for morphology, tinctorial properties (Gram stain) and the presence of plasma-coagulating activity and a flake-forming factor.
Under the microscope, Gram-stained staphylococci have the appearance of violet-blue cocci, arranged in clusters or small groups (“lace”).
Plasma coagulation activity is checked in the plasma coagulation reaction (PCR). Taking into account the results of the RCP and lecitovitellase activity in 70-75% of cases, on the fourth day of the study, the strain can be confirmed to belong to the type of Staphylococcus aureus and an appropriate response is issued.
If the culture has only plasma-coagulating or only lecitovitellase activity, then the final answer requires the determination of other signs of pathogenicity - mannitol fermentation under aerobic conditions or DNase activity.
The determination of the antibiogram is carried out only after the isolation of a pure culture. Isolated cultures of Staphylococcus aureus are subject to phage typing.
Accounting for the results of phage typing, determination of sensitivity to antibiotics, DNase activity. Final issuance of the answer.
The study of air by the sedimentation method is allowed in exceptional cases.
Petri dishes with a nutrient medium (MPA) are installed in open form horizontally on different levels from the floor. The method is based on the mechanical sedimentation of bacteria on the surface of agar in Petri dishes. The medium plates are exposed for 10 to 20 minutes, depending on the expected air pollution. Elective media are used to identify pathogenic flora. Exposure in these cases is extended to 2-3 hours. After exposure, the dishes are closed, delivered to the laboratory and placed in a thermostat for 24 hours at a temperature of 37 °C. The next day, the grown colonies are studied.
Criteria for assessing microbial contamination of air in surgical and obstetric hospitals
Sampling location
Working conditions
Permissible total number of CFU in 1 m3 of air
Permissible number of colonies of Staphylococcus aureus in 1 m3 of air
Operating rooms and delivery rooms
Before work
Not more than 500
Must not be
During work
Not higher than 1000
No more than 4
Chambers for premature and injured children
Not more than 500
Must not be
During work
Not higher than 750
Must not be
Breast milk collection and pasteurization rooms
During work
Not higher than 1000
No more than 4
Children's wards
Prepared to receive children
Not more than 500
Must not be
During work
Not higher than 750
Air microorganisms
Air as a habitat for microorganisms is less favorable than soil and water, since it contains very little or no nutrients for the reproduction of microorganisms. However, once in the air, many microorganisms can remain in it for a more or less long time. Microorganisms are distributed unevenly in the air. There are more microorganisms in dusty and dirty air than in clean air, as they are adsorbed on the surface of solid particles. The air is especially polluted near earth's surface, and as you move away from it, it becomes more and more pure. There are more microorganisms in the air of the city center, and less on the outskirts. There are more microorganisms in the air in summer, less in winter.
Microorganisms are found even in the clouds. At high altitudes, microorganisms are found that form pigments that increase their resistance to adverse living conditions, especially ultraviolet rays. Above 84 km above sea level, microorganisms are not detected.
The number and species composition of microorganisms in the air . Under natural conditions, hundreds of species of saprophytic microorganisms are found in the air, represented by cocci (including sarcins), spore-forming bacteria and filamentous fungi, which are highly resistant to ultraviolet rays and other adverse effects. external environment. The air in open spaces is relatively clean, while indoor air is much more polluted. In the air of enclosed spaces with poor ventilation, microorganisms accumulate through the respiratory tract of a person. Pathogenic microorganisms enter the air from sputum and saliva when coughing, talking, sneezing. Even a healthy person, when sneezing and coughing, releases 10 ... 20 thousand CFU into the air, and a sick person - many times more.
The number of microorganisms in the air varies over a wide range: from single bacteria to tens of thousands of CFU/1m 3 . So the air of the Arctic contains 2 ... 3 CFU per 20 m 3, and in cities with industrial enterprises a huge amount of bacteria is found in the air. In the forest, especially coniferous, there are very few microorganisms in the air; phytoncides of the forest have a detrimental effect on them. Above Moscow at an altitude of 500 m in 1 m 3 of air, from 1100 to 2700 CFU of microorganisms were found, and at an altitude of 2000m - 500-700 CFU. Spore-forming bacteria and filamentous fungi were found at an altitude of 20 km, other groups of microorganisms were found at an altitude of 61–77 km.
On average, a person inhales 12000 ... 14000 dm 3 of air per day. At the same time, 99.8% of the microorganisms contained in the air are retained in the respiratory tract.
Air pollution by pathogenic microorganisms . When sneezing, coughing and talking, many droplets of liquid are thrown into the air, inside which microorganisms are contained. These droplets can stay suspended in the air for hours; form persistent aerosols. Due to moisture, microorganisms in droplets live longer. In this airborne way, infection occurs with many acute respiratory diseases (flu, measles, diphtheria, pneumonic plague, etc.). This way of spreading pathogens is one of the main reasons for the development of not only epidemics, but also major pandemics of influenza, and in the past, pneumonic plague.
In addition to the airborne route, pathogenic microorganisms can spread through the air through the “dusty” route. This is explained by the fact that the microorganisms found in the secretions of patients (sputum drops, mucus, etc.) are surrounded by a protein substrate, so they are more resistant to drying and other factors. When these droplets dry, they turn into a kind of microbial dust containing many pathogenic microorganisms.
Microbial dust particles have a diameter of 1 to 100 microns. For particles larger than 100 µm in diameter, the force of gravity exceeds the air resistance, and they quickly settle. The rate of dust transfer depends on the intensity of air movements. Microbial dust plays a particularly important role in the epidemiology of tuberculosis, diphtheria, tularemia and other diseases.
To reduce microbial contamination of air in industrial premises apply physical ways its cleaning and disinfection. Using the system supply and exhaust ventilation polluted air is removed from the premises, and cleaner air is supplied in its place. Filtration of incoming air through special air filters greatly improves ventilation efficiency.
The most widespread method of air filtration through fibrous porous or granular materials. Although fibrous filters are at least 5 µm in diameter and have low compaction (gaps of at least 50 µm), they easily trap most microorganisms with an average size of about 1 µm.
Filters impregnated with a special dust-binding liquid trap up to 90-95% of microorganisms and dust particles in the air. After purification, the air is subjected to disinfection. Using fine air filters (FTO) it is possible to achieve a cleaning efficiency of up to 99.999%. The required degree of air purification in the room is determined by the conditions and nature of the product being produced. Modern equipment for biological treatment air provides the organization of common and special areas. The biological air purification line, as a rule, includes several technological elements working in series: an oil filter, a coarse filter, a head filter and individual fine filters. Kit individual elements in the system is determined by a specific production task.
Decontaminated air can be obtained using UV irradiation. For this purpose, the room is equipped with stationary or portable bactericidal lamps at the rate of 2.0-2.5 W / m 3 of the room volume. The operation of the lamps for 6 hours can reduce the number of microorganisms in the air by 80-90%. However, it should be borne in mind that the operation of conventional lamps should be carried out in the absence of people, since their radiation has an adverse effect on the skin, mucous membranes of the body and eyes. Air disinfection in the presence of people can only be carried out using ultraviolet bactericidal irradiators-recirculators, which are designed for periodic and continuous operation.
Usually in the air industrial premises food enterprises should contain no more than 500 CFU / m 3. For some industries, the allowable indicators of the content of microorganisms in the air are more stringent, their values are given in the regulatory documentation.
Sanitary assessment of air. The following methods are used to determine airborne microorganisms:
sedimentation (Koch method), filtration (air is passed through sterile water);
methods based on the principle of impact action of an air jet using special devices. The latter methods are more reliable, as they allow you to accurately determine the quantitative air pollution by microorganisms and study their species composition.
At the enterprises of the food industry, in production shops and in places of storage of products, it is necessary to observe a certain humidity, temperature and microbiological purity of the air.
Sanitary assessment of indoor air is carried out according to the following indicators: QMAFAnM (number of mesophilic aerobic and facultative anaerobic microorganisms); the content of mold (mycelial) fungi and yeast; the number of sanitary-indicative streptococci in 1m 3 of air.
The number of cells (CFU) in 1 m 3 of air is used to judge the degree of contamination of human nasopharyngeal microorganisms with streptococcus and, therefore, the possible presence of pathogenic microorganisms in the air.
Air is a medium containing a significant number of microorganisms. With air, they can be transported over considerable distances. Unlike water and soil, where microbes can live and multiply, they only remain in the air for a while and then die under the influence of a series of adverse factors: drying, the action of solar radiation, temperature changes, lack of nutrients, etc. The most resistant microorganisms can remain in the air for a long time and be found there with great constancy. Such permanent air microflora includes spores of fungi and bacteria, sarcins and other pigment-forming cocci.
Relevance of the topic.
It is undeniable that only a healthy person, with good health, is able to live actively, study well, and successfully overcome difficulties. The state of our health depends on a number of factors, including the quality of the air around us. Wherever people are - at work, at school or at home, when they breathe clean air, their well-being and performance improve. Therefore, it is important to know about the state of the air in those rooms where we spend most of the time. In this regard, the problem of maintaining the purity of the air in school premises, in which we spend 6-7 hours a day, is relevant for us. Most of the day today's children spend at school. Sometimes it seems to us that in our school everyone is just obsessed with cleanliness. The first thing you hear when you enter a school is: “Look how much dirt you bring on your feet, and then you will breathe this dust all day long.” “Do you know how many microbes are in this dust?” No, we don't, but I can find out how many germs are in the air in school buildings, and what factors influence this.
Objective: to identify quantitative changes in the air microflora in various school premises during the school day using the precipitation method.
To achieve my goal, I need to solve a series tasks:
1. Explore various sources information on the problem under consideration, requirements for the sanitary and hygienic state of the air in classrooms.
2. Master the techniques of working with laboratory equipment, take air samples to determine its purity.
3. Monitor the process of growth of bacterial colonies, perform calculations based on the results of the experiment.
4. To study the dynamics of the content of microorganisms in the air during the school day.
5. Develop proposals for improving the state of the air environment in the school.
Research methods:
Theoretical;
-experimental - experiments, observations, comparisons;
- mathematical - carrying out calculations.
Equipment: disposable plastic Petri dishes with dense nutrient medium (DMF), thermometer, magnifying glass, ruler, camera.
Object of study: the air environment of school premises.
Subject of study: air microflora.
Hypothesis: I assume that the air of school premises during the day is exposed to pollution, including microbial pollution, and over time, the number of microorganisms in the air increases.
Chapter I. Overview of sources of information on the research problem
1.1. Brief description of microorganisms
Most microbes belong to the group of bacteria. This group is widespread in nature, the most well studied, so the study of microbes usually begins with bacteria.
Bacteria are divided according to the shape of their cells: into spherical - cocci, rod-shaped or cylindrical - actually bacteria - and convoluted - vibrio and spirilla. In addition, there are also filamentous bacteria and myxobacteria. Between all these groups there are numerous and often not noticeable transitions, for example, cocco-bacteria and others.
Cocci, in turn, are divided according to their combination with each other into several subgroups: micrococci, diplococci, streptococci, tetracocci, staphylococci and sarcins.
Among the cocci, streptococcus, which is involved in lactic acid fermentation, has the most important practical significance. Many cocci cause various diseases in humans and animals. Streptococcus is the causative agent of angina. Staphylococci and streptococci are pyogenic microorganisms.
When the skin is damaged, various types of injury, as well as when the protective functions of the body are weakened, these microorganisms cause purulent inflammation of the skin, throat, respiratory tract, and so on. Pathogenic streptococci are also the causative agents of scarlet fever, rheumatism, secondary mixed infections, and many others. All of these pathogens can cause sepsis - blood poisoning.
Rod-shaped bacteria make up the most extensive groups.
This group includes many pathogens of infectious diseases: anthrax, brucellosis, tetanus, intestinal infections. But among the bacteria of this group there are many useful microbes, for example, intrifiers, and bacteria that absorb nitrogen from the air.
Convoluted bacteria are called spirilla if they have the appearance of a spiral with several whorls, and vibrios if they have one whorl, not exceeding ¼ of the turn of the spiral. Typical representatives of vibrios are the causative agent of cholera and water vibrios, very similar to Vibrio cholerae, but not pathogenic, common inhabitants of fresh water, as well as spirilla.
Filamentous bacteria are long threads of cells joined together. These are mainly aquatic microorganisms.
Myxobacteria (mucus bacteria) are the most highly organized bacteria. Most species have a well-formed core.
The internal structure of bacteria is still insufficiently studied due to technical difficulties in the research methodology.
1.2. Air microflora
Air microflora can be conditionally divided into constant, often occurring, and variable, whose representatives, getting into the air from their habitats, do not remain viable for long. Pigment-forming cocci, bacilli, yeasts, fungi, actinomycetes, spore-bearing bacilli and clostridia, etc., are constantly found in the air, that is, microorganisms that are resistant to light and drying. In the air of large cities, the number of microorganisms is greater than in rural areas. Over forests, seas, the air contains few microbes (in 1 m 3 - units of microbial cells). Rain and snow help cleanse the air of germs.
There are much more microbes in the indoor air than in open air pools, especially in winter, with insufficient ventilation. The composition of the microflora and the number of microorganisms found in 1 m 3 of air (microbial number of air) depend on the sanitary and hygienic regime, the number of people in the room, their state of health and other conditions.
Pathogenic microorganisms from animals, people (patients and carriers) can also get into the air.
Dust particles serve as a favorable environment for the vital activity of various microorganisms. Scientists have found 383 species of bacteria and 28 genera of microscopic fungi in the air. Sources of air pollution are soil, water, plants, animals, humans and waste products of living organisms.
The microflora of the air depends on the microflora of the soil or water, over which the layers of air are located. Microbes can multiply in soil and water, but they do not multiply in the air, but only persist for some time. Raised into the air by dust, they either settle with drops back to the surface of the earth, or die in the air from a lack of nutrition and from the action of ultraviolet rays. Therefore, the air microflora is less abundant than the microflora of water and soil. The largest number of microbes contains the air of industrial cities. The air in rural areas is much cleaner. The air microflora differs in that it contains a lot of pigmented and spore-bearing bacteria, as they are more resistant to ultraviolet rays (sarcinas, staphylococci, pink yeast, miraculous bacillus, hay bacillus and others). The indoor air is very rich in microbes, especially in cinemas, train stations, schools, livestock buildings and others.
Together with harmless saprophytes in the air, especially indoors, pathogenic microbes can also be found: tubercle bacillus, streptococci, staphylococci, pathogens of influenza, whooping cough, and so on. Influenza, measles, whooping cough are infected exclusively by airborne droplets. When coughing, sneezing, the smallest aerosol droplets containing pathogens are thrown into the air, which are inhaled by other people and, having become infected, fall ill. Microbiological analysis of air for pathogenic flora is carried out only according to epidemic indications.
The cleaner the air in public places, around human habitation and in rooms, the less people get sick. It is estimated that if you brush the vacuum cleaner over the surface of an object four times, up to 50% of germs are removed, and if twelve times - almost 100%. Forests and parks are of great importance in the fight for clean air. Green spaces precipitate, absorb dust and release phytoncides that kill microbes.
Microbes are not only harmful to human health. The pathogens of animals and plants also spread through the air. Microorganisms, together with dust, settle on food products, causing them to turn sour and putrefactive.
In a planned manner, air samples for bacteriological examination are taken in operating rooms, postoperative wards, intensive care units, intensive care units and other rooms requiring aseptic conditions. According to epidemic indications, the air of nurseries, kindergartens, schools, factories, cinemas, and so on is subjected to bacteriological examination.
Detection in the indoor air of hemolytic streptococcus group A and staphylococcus, which has signs of pathogenicity, is an indicator of the epidemic unfavorability of this object.
1.3. Sanitary and microbiological examination of air
The air environment, as an object of sanitary and microbiological research, has whole line specific features. As a rule, among them, first of all, there are:
- lack of nutrients and, as a result, the impossibility of reproduction of microorganisms;
- short-term presence of microorganisms in the air phase and their spontaneous sedimentation;
- low concentrations of microorganisms in the air;
- a relatively small number of microbial species found in the air.
Microorganisms are in the air in the form of an aerosol. A microbial aerosol is a suspension in the air of living or killed microbial cells adsorbed on dust particles or enclosed in “drop nuclei”. It includes particles ranging in size from 0.001 to 100 microns. Particle size determines 2 important parameters aerosol:
1. settling rate (sedimentation) - for particles with a size of 10 to 100 microns is 0.03 - 0.3 m/sec. Particles of the specified size settle on the surface in 5-20 minutes. Particles with a size of 5 microns or less form a practically non-sedimentary aerosol of particles constantly suspended in the air;
2. penetrating ability of particles - particles with a size of 0.05 to 5 microns are the most dangerous, as they linger in the bronchioles and alveoli. It is this fraction of dust particles that is taken into account in modern classification clean rooms according to GOST R 50766 - 95. Particles with a size of 10 microns or more are retained in the upper respiratory tract and removed from them.
The danger of microbial aerosol to human health is due not only to the existence of an aerosol transmission mechanism in a number of infectious diseases. Microbial aerosol can also cause the development of allergies, as well as intoxications (poisoning) associated with inhalation of endotoxins of gram-negative bacteria, gram-positive bacteria and mold mycotoxins. In addition, the presence of microbial aerosols in the air is undesirable in the implementation of a number of technological processes.
1.4. Methods of microbiological studies of the qualitative and quantitative composition of bacteria in the air
For studying various properties microbes in microbiology, a method has been developed for their artificial cultivation on special media. Microorganisms in natural conditions usually found in communities of various species. An accurate study of individual species is possible only if they are isolated in pure cultures, that is, in cultures containing only one type of microbes. Pasteur was the first to develop special methods for the study of microbes. Further improvement of the methods of bacteriological research belongs to the leading German scientist R. Koch.
Currently, they use natural and artificial media, liquid and dense. Natural media include: skimmed milk, unhopped wort, pea decoctions, potato slices, and others. There are a lot of artificial environments. For heterotrophic bacteria, media with peptone is used. Peptone is a product of incomplete breakdown of animal proteins. Such is peptone water (1 g of peptone, 0.5 sodium chloride per 100 ml of water). In meat-peptone broth, the same amount of peptone and salt is added to meat broth from which proteins are precipitated. These liquid media can be solidified by adding 1-3% food agar to them. Agar is a substance extracted from seaweed. Its value is that the agar medium solidifies in the form of a transparent jelly and does not liquefy if it is not heated to a boil. The environment must have a certain reaction (pH), must be sterile. Crops are grown at a certain temperature. Meat-peptone agar is very widely used in microbiology, since almost all types of microorganisms grow on this substrate, and therefore, it is applicable for the primary identification of air bacteria.
In the study of indoor air, the method of isolating microorganisms from the air is of great importance. Depending on the principle of trapping bacteria, microbiological methods for studying air are divided into sedimentation, filtration and aspiration methods. The method of natural sedimentation is based on the sedimentation of microorganisms under the action of gravity on the surface of a dense nutrient medium. An open Petri dish with a nutrient medium is left on a horizontal surface for a certain time. Then the cup is closed and after incubation in a thermostat, the grown colonies are counted. It should be noted that the results obtained in this case turn out to be underestimated, in comparison with the data obtained using the Krotov device, by an average of three times, since fractions with particles smaller than 100 μm practically do not settle. In this regard, attempts were repeatedly made to correct the calculation scheme, but they did not end with the development of a generally recognized calculation method. At present, many authors, citing the results of measurements made using the sedimentation method, limit themselves to indicating the number of colonies, the time of sampling, and the diameter of the Petri dish. To determine the type of microbes crucial have: features of the surface of the colonies (smooth, rough, convex, bumpy), its edges (smooth, jagged), color, size of the colonies.
The number of microbes in working and residential premises is closely related to the sanitary and hygienic regime of the premises: the size of the premises, lighting conditions, the quality of cleaning, the frequency of ventilation and other factors. With crowds of people, poor ventilation, poor natural light, improper cleaning of the premises, the number of microbes increases. Dry cleaning, infrequent washing of floors, the use of dirty rags and brushes, and drying them in the same room create favorable conditions for the accumulation of microbes in the air.
The sanitary and hygienic condition of indoor air is determined by two indicators:
microbial number - the content of the total number of microorganisms in 1 m 3 of air;
the number of sanitary-indicative bacteria - hemolytic streptococci and pathogenic staphylococci in 1 m 3 of air;
Particularly strict sanitary and hygienic requirements are imposed on the air of operating rooms, maternity hospitals, hospital wards and children's institutions.
Used for indoor air disinfection germicidal lamps different power. Irradiation of air with such lamps leads to rapid inactivation and complete death of viruses and bacteria. Sometimes, for disinfection of indoor air, the method of spraying chemical antiseptics - propylene glycol, triethylene glycol, which are odorless and non-toxic to humans, is used.
Microbes can be spread by air currents, airborne dust and airborne droplets. The pathogens of influenza, measles, acute respiratory infections, scarlet fever, diphtheria, whooping cough, tonsillitis, tuberculosis and other diseases can be transmitted through the air along with drops of mucus and sputum when sneezing, coughing, talking. When sneezing, coughing, talking, a sick person throws out pathogenic bacteria along with drops of mucus, sputum environment with a radius of 1 - 1.5 m or more.
Pathogenic microorganisms can be transmitted through the air by airborne dust. 1 g of dust contains up to 1 million particles. various bacteria including pathogenic fungi. Pyogenic streptococci and staphylococci, mycobacterium tuberculosis, anthrax bacilli, tularemia bacteria, salmonella, etc. can be transmitted by airborne dust.
During epidemics, in order to protect people from infection with pathogenic microorganisms through the air, mandatory wet cleaning and frequent ventilation of rooms, cotton-gauze masks, burning or disinfection of sputum of patients is recommended.
Chapter II. Research methodology
The study of air microflora was carried out in November 2014 in the premises of MBOU secondary school No. 18 of the village of Kislyakovskaya and included a number of stages:
1. Preparation of an artificial nutrient medium.
2. Growing microorganisms by precipitation from the air.
3. Quantitative calculation of microorganisms in the air.
4. Statistical processing of the material and analysis of the data obtained.
2.1. Preparation of artificial nutrient medium.
First, at home, I prepared meat-peptone broth from beef meat (I passed 500 g of meat without bones and fat through a meat grinder). Minced meat in an enamel pan was filled with water (1 liter) and left for 24 hours at a temperature of 7°C. Then the minced meat was boiled for 30 minutes. Cooled and filtered. Then I added 1 g of salt and 1 g of peptone to 100 g of broth, brought it to a boil again and filtered a second time. I added a 10% solution of baking soda to neutralize the broth to a slightly alkaline reaction. In the resulting MPB added 20 g of gelatin. Received meat-pepton gelatin. I sterilized the Petri dishes, poured the same amount of NRM into them and closed them, left them to solidify.
2.2. Growing microorganisms by precipitation from air.
To determine the presence of microorganisms in the air, I used the method of growing them on culture media, inoculating directly on a nutrient medium (Koch's sedimentation method). The Koch settling method is used only in the study of indoor air and is suitable for comparative assessments of air purity. The degree of air pollution is judged by the number of grown colonies.
First, together with the teacher, they identified rooms for research. We chose rooms where the temperature was the same (20-22 ° C): geography room - No. 11 (sunny side), chemistry / biology room (shady side) - No. 12, corridor of the 1st floor, school canteen and dressing room.
Wardrobe
1st floor corridor
Dining room
Office number 11
Office number 12
Microbiological analysis was carried out three times during one day: early in the morning, before the students arrived; then at the third break, with the active movement of schoolchildren, and after the sixth lesson until wet cleaning.
Petri dishes filled with meat-peptone gelatin, pre-numbered with a marker, were placed at the indicated points and left open for 10 minutes. Along with dust and moisture droplets, microbes also settle on the surface of the NRM. At the end of the set time, the cups were closed with lids, placed in a self-made thermostat and kept in the biology laboratory at t 25ºС for 7 days.
2.3. Quantification of microorganisms in the air
After 7 days, the grown colonies are counted, assuming that each colony has grown from one settled microbial cell. It has been established that in 10 minutes, the amount of microorganisms contained in 10 liters of air will settle on an area of 100 cm 2.
Knowing the number of colonies that have grown in a Petri dish and its area (at 9 cm it is 63.6 cm 2), it is possible to calculate how many microorganisms are contained in 10 liters of air. So, if A microorganisms settle on an area equal to 63.6 cm 2, then X microorganisms are contained on an area equal to 100 cm 2:
Multiplying the result by 100, determine the content of microorganisms in 1 m 3, or in 1000 liters of air
The description of colonies of microbes grown on a nutrient medium is carried out according to the following indicators: shape (round, irregular); surface (smooth, shiny, rough, dry, wrinkled); edge (smooth, wavy, crenate); color; size (diameter).
It should be noted that the method of counting colonies in petri dishes with inoculation from air gives only approximate data. Only microbes of rapidly settling dust are taken into account, in addition, only aerobic forms of microorganisms will germinate on a solid nutrient surface. Sedimentation sampling method (Koch) does not allow to determine the exact number of microorganisms in the air, it gives only an approximate assessment of the microflora. However, the results of such studies allow one to obtain big picture air pollution.
2.4. Carrying out statistical processing of the material
Statistical processing of the obtained data was carried out according to the method of B. A. Dospekhov.
Accounting for the sowing of bacteria from the air is carried out by counting the grown colonies of bacteria separately. Knowing the area of the Petri dish, you can determine the number of microorganisms in 1 m 3 of air. For this:
1) the area of the nutrient medium in the Petri dish is determined by the formula πr 2 ;
2) calculate the number of colonies in an area of 1 dm 2 ;
3) recalculate the number of bacteria per 1 m 3 of air.
Approximate calculation:
In a Petri dish with a diameter of 10 cm, 25 colonies grew.
1) determine the area of the nutrient medium in the Petri dish according to the formula 3.14 * 5 2 = 3.14 * 25 = 78.5 cm 2
2) calculate the number of colonies on an area of 1 dm 2 equal to 100 cm 2
25 colonies - 78.5 cm 2
x \u003d 25 * 100 / 78.5 \u003d 32 colonies
x colonies - 100 cm 2
i.e., on an area of 1 dm 2 there are 32 colonies.
3) recalculate the number of bacteria per 1 m 3 of air, which is equal to 1000 liters. The 32 colonies of bacteria contained in an area of 1 dm 2 correspond to a volume of 10 liters of air. To find out the amount in 1 m 3 of air, make up the proportion:
32 – 10
x \u003d 32 * 1000 / 10 \u003d 3200
x - 1000
Therefore, 1 m 3 of air contains 3200 bacterial bodies.
Chapter III. Results and its discussion
During the studies, three Petri dishes were used for each microbiological assessment. Colonies of microorganisms grown on the NRM medium are shown in the photo (the results of microbiological analysis at the 3rd change):
Office number 11
Office number 12
Dining room
Wardrobe
1st floor corridor
Based on the count of colonies grown in Petri dishes, an assessment was made of the content of microorganisms that are contained in the air various premises at different times of the school day.
The results of this study were compared with the criteria for the sanitary assessment of the air in residential premises (Table No. 1) and presented in Table No. 2.
Table number 1. Criteria for sanitary assessment of indoor air
Table 2. The number of microorganisms contained in 1 m 3 of air in school premises during the school day
Then a comparative analysis of the microflora of school premises was carried out throughout the school day (Diagrams 1-3).
Diagram 1. Sanitary assessment of air in the premises of Kislyakovskaya MBOU secondary school No. 18 in the morning (microorganisms in 1m 3)
Chart 2
Diagram 3. Sanitary assessment of indoor air in Kislyakovskaya MBOU secondary school No. 18 after the 6th lesson (microorganisms in 1m 3)
Revealed a trend towards an increase in the number of microorganisms in all school premises compared with the morning test, which, apparently, is associated with the intensity of human movement. Based on the data obtained, the room most contaminated with microorganisms is the dressing room, the corridor of the 1st floor, then office No. 12, the dining room and office No. 11.
The high pollution of the dressing room is explained by the high intensity of people's movement, all 134 students of the school pass through it, and air was taken during the undressing and dressing of students, which increased the circulation of dust - the main carrier of microorganisms. The high pollution of the corridor on the 1st floor is explained by the fact that there is a higher air temperature of +24°С and high traffic intensity throughout the school day. Based on the fact that microorganisms multiply abundantly in warm and humid environments, on the remains food products, on dust particles in darkened areas of the premises, we can say that the high microbial content found in the premises is natural. The increased number of microorganisms after the lessons can be explained both by the increase in air pollution towards the end of the school day and by the intensity of traffic. But the level of microbial contamination, based on the standards, in all rooms, except for the wardrobe, is not exceeded.
The air in classroom No. 11 and the dining room after the 6th lesson turned out to be cleaner compared to other rooms, this can be explained by the fact that wet cleaning has already taken place. A small number of colonies of microorganisms in room No. 11 indicates that there are no favorable conditions for their development (sunny side).
Work Conclusions
The results of the study generally confirm my hypothesis.
1. The smallest number of microorganisms was found in the air samples of the first experiment (in the morning).
2. The level of microbial contamination in the premises of the Kislyakovskaya MBOU secondary school No. 18, except for the wardrobe, does not exceed the standard.
3. The indoor air does contain bacteria, the number of which increases during the day under the influence of various factors.
4. When found a large number people indoors, the number of microorganisms in the air increases.
5. Wet cleaning and ventilation of the room help reduce dust and bacteria in the air.
1. To oblige the attendants at a big break to open the windows.
2. Clean the premises more often with the use of disinfectants.
3. Clothes must be given out by a wardrobe worker through a window or door.
4. At the entrance to the school, lay out rugs that remove mechanical dirt from shoes.
Conclusion
So, at this stage of my project, I can say that germs enter the air mainly with rising dust, so keeping the rooms clean is very important. Together with the teacher, we plan to continue our research in the warm season and compare the results obtained with the data of this work. In addition, it is possible to conduct a comparative analysis of one room in different periods of time in the presence of additional factors:
1) ventilation of the room,
2) the number of people and the intensity of their movement,
3) the effect of phytoncidal activity of plants on the microflora of school premises.
We did not take air samples in the gym due to its renovation, which is planned to be done in the future.
Well, my little observation, which is based not only on scientific, but also on everyday experience. Students elementary school always change into a change of shoes, but middle and senior students are often too lazy to do this. As it turned out, in vain. Creating a safe environment around us, schoolchildren, is a concern not only for cleaners or teachers on duty, but also for ourselves.
List of information sources used
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10. http://www.webmedinfo.ru/library/mikrobiologija.php
11. http://ayp.ru/spargalki/biologiya/1/Page-19.php
12. http://www.ebio.ru/gri06.html
Work completed:
Rud Sofya Grigorievna
7th grade student MBOU secondary school No. 18
Scientific adviser:
Fomenko Elena Vladimirovna
teacher of chemistry, biology MBOU secondary school No. 18
Municipal budgetary educational institution
basic comprehensive school No. 18
Krasnodar region
Kushchevsky district
stanitsa Kislyakovskaya
2014